Symposium Organizers
Richard B. Jackman University College London
Christoph Nebel National Institute of Advanced Industrial Science and Technology
Robert J. Nemanich Arizona State University
Milos Nesladek Commissariat Energie Atomique (CEA/Saclay)
P1: Keynote Session
Session Chairs
Monday PM, November 26, 2007
Independence W (Sheraton)
11:30 AM - **P1.1
Mechanisms of Self Assembly at Nanoscale Dimensions.
Harold Kroto 1
1 Chemistry and Biochemistry Department, The Florida State University, Florida, Florida, United States
Show Abstract12:00 PM - **P1.2
Atomic-scale Studies of Diamond Surfaces.
Gerald Dujardin 1 , E. Boer-Duchemin 1 , G. Cometet 1 , A. Mayne 1 , E. Tranvouez 1
1 Laboratoire de Photophysique Moleculaire, University of Paris - Sud, Orsay France
Show AbstractClean and hydrogenated diamond surfaces have outstanding optical, electronic and chemical properties which make them unique candidates for fabricating nanometer-scale devices such as nano-sources of photons or electrons and biological nano-sensors. For that purpose, we have investigated the atomic-scale properties (topography, electronic structure, electronic conductivity and adsorption of nanoparticles) of clean and hydrogenated diamond C(100) surfaces by using the STM and the AFM.
12:30 PM - **P1.3
Luminescence of Blue Diamonds: Donor-Acceptor Pair Recombination?
James Butler 1
1 Chemistry, Naval Research Laboratory, Washington, District of Columbia, United States
Show AbstractLuminescence experiments were performed on a large sampling of natural blue and gray diamonds including the Hope Diamond and Blue Heart diamond. Nearly all of the 66 diamonds examined showed a combination of aqua (500 nm) and red (660 nm) phosphorescence. The red phosphorescence of natural blue diamonds, previously thought to be a rare phenomenon, is shown to be quite common. A few natural and high pressure, high temperature (HPHT) synthetic stones were also studied using cathodoluminescence (CL), laser-induced photoluminescence (PL), and time-resolved PL to better determine the defects responsible for the observed luminescence. The data are compared with previous research performed on synthetic diamonds. Variation in the phosphorescence with temperature provided evidence that donor-acceptor pair recombination was the responsible mechanism for at least one of the observed phosphorescence peaks.
P2: Diamond Electrochemistry
Session Chairs
Monday PM, November 26, 2007
Independence W (Sheraton)
2:45 PM - **P2.1
Optically Transparent Diamond Electrodes for Chemical Analysis.
Yingrui Dai 1 , Jerzy Zak 2 , Denis Proshlyakov 3 , Greg Swain 1
1 Department of Chemistry, Michigan State University, East Lansing, Michigan, United States, 2 Faculty of Chemistry, The Silesian Technical University, Gliwice Poland, 3 Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan, United States
Show AbstractElectrically conducting diamond is an advanced carbon electrode material that is proving to be useful for several electrochemical technologies. In fact, few materials show as much versatility as an electrochemical electrode as does boron-doped, chemical vapor deposited (CVD) diamond. The material can be used in electroanalysis to provide low detection limits for analytes with superb precision and stability; for high-current density electrolysis (> 1 A/cm2) in aggressive solution environments with little microstructural or morphological degradation; and as an optically transparent electrode (OTE) for spectroelectrochemical measurements in the UV/Vis and IR regions of the electromagnetic spectrum. The application of optically transparent electrodes (OTEs) for spectroelectrochemical measurements in the UV-Vis and IR regions of the electromagnetic spectrum represents a new field of diamond research. This new OTE possesses properties that are superior to those of conventional UV-Vis OTEs, like indium tin oxide (ITO). These properties enable its use in measurements and chemical environments where conventional OTEs fail. The growth and characterization of optically transparent diamond electrodes for use in transmission spectroelectrochemical measurements in the UV-Vis and IR regions of the electromagnetic spectrum will be discussed. Diamond-quartz electrodes were used to study the electrochemical and optical properties of aqueous (Fe(CN)6-3/-4) and non-aqueous (ferrocene) redox systems in the UV-Vis region, while diamond-undoped Si electrodes were used to study the electrochemical and optical properties of these same redox systems in the mid- and far-IR. Studies of structure-function relationships of redox proteins (e.g., cytochrome c and myoglobin) using spectroelectrochemical methods will also be discussed.
3:15 PM - **P2.2
Application for Electrochemical Sensors using Boron-doped Diamond Electrodes.
Yasuaki Einaga 1
1 Chemistry, Keio University, Yokohama Japan
Show AbstractConductive boron-doped diamond (BDD) electrodes are very attractive material because of their wide potential window, low background current, chemical inertness, and mechanical durability. Here, we several examples for electrochemical applications by using bare BDD electrodes and modified BDD electrodes will be discussed. (1)Glucose: Cu-implanted BDD electrodes: The detection of glucose is very important. However, glucose is normally undetectable using bare BDD electrodes. The glucose oxidation is a complicated process that requires a catalytic reaction using an enzyme or active metal surfaces. Although Au, Pt, Ni and Cu metal electrodes are known for showing electrocatalysis for the glucose oxidation, BDD electrode does not have the catalytic properties. In the present work, we have studied electrochemical detection of glucose using Cu-modified BDD electrode (Cu-BDD). We report the simple method of selective glucose detection using the Cu-BDD. The selectivity was derived from the differences in the diffusion processes for interfering species such as ascorbic acid and uric acid (linear diffusion on BDD) and for glucose (spherical diffusion on implanted copper). Each dispersed copper particle of the Cu-BDD act as an ultra microelectrode because glucose react only at copper surface but not BDD surface. On the other hand, interfering substances react at both of two electrodes. Eventually the difference of diffusion leads to dependence or independence of the Faradic current on time, and a steady-state component of the current reflects only glucose concentration.(2)Proteins (BSA, IAP): A development of simple and wide detection range protein detection methods are much increasing attention because the early detection of biomarkers such as cancer markers is very crucial. We have succeeded in the direct electrochemical detection of proteins including cancer markers in the range of in vivo concentration by using BDD electrodes.(3)Arsenic : Au-modified BDD electrodes: Electrochemical separate detection of As(III) and As(V) was realized by using Au-deposited BDD electrodes. Catalytic activity realized a high sensitivity detection of them (detection limit : 0.5 ppb) by using linear sweep stripping voltammetry. References [1] Y. Einaga, A. Fujishima, et al.(Ed.) Diamond Electrochemistry, Elsevier/BKC-Tokyo 2005. [2] Y. Einaga, et al., Diamond Relat. Mater., 14, 2133 (2005)., Anal. Chem., 78, 3467 (2006)., Anal. Chem., 78, 6291 (2006)., Anal. Chem., 78, 7857 (2006).
3:45 PM - P2.3
Functionalization of Diamond Surfaces for Electrochemical Sensing of Nitric Oxide (NO).
James Sund 1 , Jeffrey Glass 1 , Scott Wolter 1 , Charles Parker 1 , Eric Toone 2 , Corey Causey 2 , Brian Stoner 3
1 Electrical and Computer Engineering, Duke University, Durham, North Carolina, United States, 2 Chemistry & Biochemistry, Duke University, Durham, North Carolina, United States, 3 Advanced Technologies, Research Triangle Institute International, Research Triangle Park, North Carolina, United States
Show AbstractThe medical community is interested in the important roles that nitric oxide (NO) plays within the human body including vasodilation, anti-infection, and neurotransmission. The research presented here integrates engineering, physical and biological sciences with the goal of developing a biocompatible sensor for detecting NO and variants like NO
2- in aqueous environments.
Diamond has many desirable attributes for sensing analytes including chemical stability and a large electrochemical window for detecting analytes in solution by reduction or oxidation. A diamond sensor can also be made more selective by limiting the molecular interactions between analytes and the surface through surface attachment of functional groups that have a higher affinity for specific classes of analytes. For example, a thiol (R-SH) can bind nitrogen oxygen (NOx) species for sufficiently long periods. The binding event can be detected through electrochemical methods by applying a ramping voltage and measuring current that begins to flow at specific voltages. Polycrystalline boron-doped* diamond was grown using microwave plasma chemical vapor deposition. The surface, as deposited, was hydrogen terminated.
Two processes for functionalizing the surface with thiol containing molecules will be presented. Both processes use deep UV photons to excite surface electrons that convert terminally double bonded molecules into surface attached molecules with diamond thus forming a chemically stable C-C covalent bond. The first process photochemically adds the surface tether, which contains an amine (R-NH-). Various chemical steps follow including deprotection, SN2 chemistry, and radical induction until a thiol terminal group is achieved. A second method for functionalizing the diamond surface is to chemically synthesize a thiol molecule that contains a double bond on the opposite end for photochemical attachment, e.g. CH2=CH-R-SH. This second method or process would reduce exposure of the diamond-silicon substrate to the various chemical processes and would ensure a homogenously functionalized surface. X-ray photoelectron spectroscopy analysis was used to confirm C 1s core level spectra changes in components and chemical shifts and supported by N 1s and S 2 p core level peaks. In the first process, the structure of the surface molecule changes with each chemical step and hence C 1s binding energy shifts arise in the XPS spectrum as attached hydrocarbons are modified. These oxidation of NO or reduction of NO2 during cyclic voltammetry occur at certain applied potentials. The additional activity of NO binding with RSH diminishes the RS reduction peak. The combination of peaks serves as a signature for identifying each species.
*Acknowledgements: BDD Samples provided by Taka Tachibana, Kobe Steel, Ltd., Electronics Research Laboratory. 1-5-5 Takatsukadai, Nishi-ku, Kobe 651-2271 Japan.
4:00 PM - P2: Electrochem
BREAK
P3: Biotechnology I
Session Chairs
Monday PM, November 26, 2007
Independence W (Sheraton)
4:30 PM - **P3.1
Towards Diamond Based Neuroelectronics.
Andreas Offenhausser 1
1 , Forschungszentrum Juelich, Juelich Germany
Show AbstractThe bio matter–solid state interfacing is anticipated to be one of the key technologies and synergies of 21st century with emerging potentials in smart sensing and applications interests in biology, food industry, biotechnology, communications and medicine. On a long term one of most fascinating topics is the cell and neuron interfacing. The coupling of neurons to micro- and nanoelectronic devices with possibility of future non-invasive long-term neural signals recording from large number of neurons within artificial or natural neural networks can ultimately lead to ground-breaking changes in current communication sciences.In order to establish a two-way interface between a neuron and an electronic device, we have followed several approaches. On the one side we focused on the detection of extracellular neuronal signals with electronic devices. In order to study the signal transfer between cell and sensor spot, we recorded signals from different cell types with microelectronic devices and used classical patch-clamp measurements for comparison. The obtained signals were described by simplified coupling models. On the other side we used the electronic devices for extracellular stimulation of excitable cells.Interfacing of electronic systems with single cells or defined networks of neurons implies the patterning of neurons to control soma adhesion on sensor array and to guide neurites. Neurons connections is of great interest in the field of cell-based bioelectronics and neuroelectronics circuits. The in vitro network architecture of neurons can be controlled by chemical patterning methods. Using microcontact printing we applied micro- and nano pattern of biomolecules (extracellular matrix proteins, biopolymers) which promote defined cell attachment to a highly cell repellent background. Cells are forced to align with the pattern and cell-cell interactions are limited to predefined pathways. A particularly challenging approach aims at not only controlling neurons growth but additionally the direction of signal transduction in the network (neuronal polarity and synaptogenesis).
5:00 PM - P3.2
Topographical Evolution of and Osteoblast Interactions with Nanocrystalline Diamond.
Lei Yang 1 , Abhishek Kothari 1 , Brian Sheldon 1 , Thomas Webster 1 2
1 Engineering, Brown University, Providence, Rhode Island, United States, 2 Orthopedics Surgery, Brown University Medical School, Providence, Rhode Island, United States
Show AbstractThe potential of nanocrystalline diamond films (NDF) for biological applications has been addressed by a variety of recent researchers. In the present work, we consider the topographical evolution of NDF fabricated by microwave plasma assisted chemical vapor deposition (MPCVD), in conjunction with a detailed study of osteoblast (bone forming cells) growth on NDF with various topographical features. The NDFs were grown with 0.5~1% methane, 2%~30% hydrogen and argon. Scanning electron microscopy (SEM) images reveal that the nano diamond grains evolve from round shapes into platelet and successively cubic shapes as the hydrogen increases. Atomic force microscopy (AFM) analysis confirms this evolution as well as the variation of the surface roughness. The mechanisms responsible for the topographical evolution are discussed. Importantly, interactions between osteoblast and NDFs were investigated by cell adhesion and proliferation assays. Results demonstrate that the osteoblast adhesion and proliferation on NDF varies dramatically depending on different topographical profiles of the films. Further observation by SEM and contact angle measurements suggests that the differences in osteoblast adhesion and proliferation are relative to the type of nano roughness (such as the local profile of the NDF surfaces). In this manner, the present study provides crucial information to those pursuing the use of NDF for orthopedic applications as it outlines which topographical features of NDF promote osteoblast functions.
5:15 PM - P3.3
Transparent Diamond MEA for Neurals Ex-vivo Experiments.
Mathias Bonnauron 1 , Samuel Saada 1 , Lionel Rousseau 2 , Blaise Yvert 3 , Philippe Bergonzo 1
1 Laboratoire de Technologies de Détecteurs, CEA, LIST, Gif-sur-Yvette France, 2 ESYCOM, Groupe ESIEE, Noisy-le-Grand France, 3 CNIC - UMR 5228, CNRS & Université de Bordeaux, Bordeaux France
Show AbstractNowadays developments in neuroscience require to study neural networks at a multicellular level. This can be achieved using Micro Electrodes Arrays (MEA) either in vivo or in vitro. In vitro MEA studies use both recording and stimulation of neural tissues and require to be as near as possible from several tens of cells. MEAs have to be very dense with high aspect ratio electrodes in order to reach undamaged cells above edges of the slice. Several systems, using inert metals such as platinium, have already been developed and demonstration has been made for their ability to record neural signals. However exciting cells without electrode damage during long lasting experiment is still difficult due to irreversible reactions that can take place at the electrode surface such as water hydrolyzation. Furthermore, most of this study requires transparent support in order to correlate electrical and biochemical activity using conventional fluorescent imaging techniques. Here, we propose to fabricate high aspect ratio diamond MEA onto glass substrates using both nanoseeding techniques and RIE diamond etching. Such system combines high electrode reactivity with high current injection limits further to be biocompatible, chemically resilient, and transparent. This system has been characterized using HRSEM, Cyclic Voltammetry and the performances of these arrays are expected to be superior to those of standard MEA during ex-vivo experiments.
5:30 PM - P3.4
Study of Cell Attachment on Undoped and B-Doped Nanodiamond Films.
Alex Kromka 1 , Petra Bilkova 1 , Lubica Grausova 2 , Lucie Bacakova 2 , Vera Lisa 2 , Frantisek Fendrych 1 , Milan Vanecek 1 , Milos Nesladek 3
1 Institute of Physics, Academy of Sciences of teh Czech Republic, Prague 6 Czech Republic, 2 Institute of Physiology, Academy of Sciences of the Czech Republic, Prague Czech Republic, 3 DRT-LIST, CEA Saclay, Gif sur Yvette, 91191 Czech Republic
Show AbstractCVD diamond attracts interests as a biocompatible material for application to medicine, due to its unique surface properties suitable for biomolecule and cell attachment. Additionally the mechanical properties of diamond make this material suitable for applications for medical implants. In this work the surface microarchitecture is the main target of our investigations in order to improve the cell and tissue attachment to implants. Also a little is known about the influence of surface wettability and electrical properties on the adherence of cells, via binding to inorganic cations incorporated in the substrate material (doping) as well as by cationic amino-acids and proteins attached to a charged surfaces[1]. In this study, we investigated preparation of undoped and B-doped nanocrystalline diamond films with different surface roughness and the different B-doping levels. The surface modification comprising hydrogenation and oxidation plasma treatment has been used to investigate the influence of the surface wettability on the cell growth. Further on, the adhesion, growth, viability and differentiation of human osteoblast-like MG 63 cells have been studied in cultures on H- or O-terminated nanocrystalline diamond (NCD) films deposited on glass and silicon substrates. The cell attachment, spreading, proliferation, viability, cytoskeletal organization and osteocalcin production have been studied by fluorescence methods. Our results suggest that the nanocrystalline diamond films support well adhesion, growth and differentiation of osteogenic cells and could be used for surface modification of bone implants (e.g., bone-anchoring parts of joint prostheses or bone replacements) in order to improve their integration with the surrounding bone tissue.[1] Ohgaki M, Kiziki T, Katsura M, Yamashita K. , J Biomed Mater Res 2001; 57: 366-373.
5:45 PM - P3.5
Diamond Nanoparticles as Photoluminescent Nanoprobes for Biology.
Francois Treussart 1 , Orestis Faklaris 1 , Alexandra Elli 2 , Vandana Joshi 2 , Jean-Paul Boudou 4 , Thierry Sauvage 3 , Patrick Curmi 2 , Jean-Francois Roch 1
1 Laboratoire de Photonique Quantique et Moleculaire, Ecole Normale Superieure de Cachan, Cachan France, 2 Laboratoire Laboratoire Structure-Activité des Biomolécules Normales et Pathologiques, INSERM U829 et Université Evry-Val d'Essonne EA 3637, Evry France, 4 Laboratoire BioEmCo, UMR 7618 , CNRS/Université Pierre et Marie Curie, Paris France, 3 Centre d’étude et de recherche par irradiation, CNRS, Orléans France
Show AbstractMonday, Nov 26Transferred Poster P15.27 to P3.5 @ 4:45 PMDiamond Nanoparticles as Photoluminescent Nanoprobes for Biology. Francois Treussart
Symposium Organizers
Richard B. Jackman University College London
Christoph Nebel National Institute of Advanced Industrial Science and Technology
Robert J. Nemanich Arizona State University
Milos Nesladek Commissariat Energie Atomique (CEA/Saclay)
Tuesday AM, November 27, 2007
Independence W (Sheraton)
9:30 AM - **P4.1
Recent Advances in High Growth Rate Fabrication of Single Crystal CVD Diamond.
Russell Hemley 1 , Chih-Shiue Yan 1 , Szczesny Krasnicki 1 , Yufei Meng 1 , Qi Liang 1 , Joseph Lai 1 , Hai-Yuan Shu 1 , Thomas Yu 1 , Ho-kwang Mao 1
1 , Carnegie Institute of Washington, Washington, District of Columbia, United States
Show AbstractLarge single crystal diamond is needed for a broad range of scientific and technological applications. We report continued advances in microwave plasma chemical vapor deposition (MPCVD) techniques in our laboratory to produce large diamond single crystals at high growth rates. The types of reactant gases and their concentrations have been varied to optimize diamond quality and growth rates. The deposited diamond has been characterized by a variety of spectroscopies and diffraction techniques. We have repeatedly grown single-crystal CVD diamonds over 10 carats and above 1 cm in thickness at growth rates of 50-100 /u/m/h. Near-colorless single-crystal CVD diamond has been produced by further optimizing the process. Residual color of colored diamond has been altered and removed have been removed by post-growth treatments, processes that can also alter the mechanical properties. Other methods to enlarge the size have been explored.
10:00 AM - P4.2
Microstructural Features at the Diamond/Iridium Interface of Heteroepitaxial Diamond on (001)Iridium/Strontium Titanate.
Richard Anderson 1 , Douglas Medlin 1 , Brage Golding 2
1 , Sandia National Laboratories, Livermore, California, United States, 2 , Sandia National Laboratories, Livermore, California, United States
Show AbstractThe synthesis of diamond by chemical vapor deposition (CVD) on non-diamond substrates (heteroepitaxy) holds the promise of wafer-scale production of single crystalline diamond. Currently the preferred technique is growth on an oriented layer of (001) iridium on a crystalline dielectric such as strontium titanate or sapphire, with the crucial step of bias-enhanced nucleation (BEN) to initiate the process. Microstructural defects at the diamond/iridium interface may limit the application of such diamond for electronic purposes. To understand this microstructure more fully we have synthesized heteroepitaxial diamond on (001) iridium over strontium titanate with various BEN exposure times, and differing layer thicknesses of diamond. HRTEM micrographs of the diamond/iridium interface region show a rich microstructure, including misfit dislocations and stacking faults along <111>. We will present a description and analysis of these defects, and their extension into the growing diamond layer.This work was funded by the Transformational Research and Development Directorate of the Domestic Nuclear Detection Office of the Department of Homeland Security, and performed at Sandia National Laboratories, which is operated under USDOE contract # DE-AC04-94AL85000
10:15 AM - **P4.3
Surface Behavior of Heterosubstrates during the Early Stages of BEN-MPCVD: a Key for Heteroepitaxy.
Jean-Charles Arnault 1
1 DSM/DRECAM/SPCSI, CEA Saclay, Gif sur Yvette France
Show AbstractDiamond heteroepitaxy is a major challenge to grow in large scale high quality diamond films devoted to active electronics. At the present time, the best diamond (100) epitaxial layers have been grown on iridium and 3C-SiC using the Bias Enhanced Nucleation (BEN) technique. Diamond (111) highly oriented films have been also grown on Pt substrates using a different nucleation procedure combining seeding and annealing steps. Competing mechanisms taking place during diamond nucleation may have detrimental consequences on the quality of the diamond/substrate interface. Indeed, the ideal heterosubstrate must demonstrate an excellent stability under Microwave Plasma Chemical Vapour Deposition (MPCVD) conditions and be rather insensitive to competing reactions (etching by hydrogen radicals, carbide formation, surface roughening, carbon dissolution into the substrate). The present talk will first give an overview on the state of the art of diamond heteroepitaxy. For several heterosubstrates (3C-SiC, Ir, Si), the surface behaviors under BEN-MPCVD conditions will be compared. These studies have been in situ performed with a MPCVD reactor connected to a UHV analysis chamber. The influence of the competing mechanisms on diamond nucleation and on the interface formation will be discussed.
10:45 AM - P4.4
Formation of Diamond (Nano)spheres at High Pressures and Temperatures.
Andreas Zerr 1 2 , Gerhard Miehe 3 , Veronique Buschmann 3 , Hartmut Fuess 3 , Reinhard Boehler 2
1 , LPMTM-CNRS, Université Paris Nord, Villetaneuse France, 2 , MPI for Chemistry, Mainz Germany, 3 Materialwissenschaft, Technische Universität Darmstadt, Darmstadt Germany
Show AbstractDiamond spheres having diameters between about 20 nm and 5 μm were formed by decomposition of long chain alkanes such as octadecane, C18H38, or nonadecane, C19H40, at high pressures and temperatures. Experiments were performed in a laser heated diamond anvil cell at pressures between 10 and 20 GPa where the starting materials were heated with the radiation of a CO2-laser to temperatures around 3000 K. Solid agglomerates obtained after heating and recovery to ambient conditions were examined using Raman spectroscopy and scanning electron microscopy (SEM). The Raman spectra have shown only one band at 1333 cm-1 which corresponds to diamond. From the SEM measurements followed that the main part of the product consisted of crystals with sharp edges or of polycrystalline crusts of irregular shape. However, on the surface of the agglomerate we found numerous spheres of nearly perfect shape having diameters between 20 nm and 5 μm. Electron diffraction measurements performed on individual spheres using a transmission electron microscope provided the evidence that the spheres consist of a material having the diamond structure. This finding incites speculations on the slope (dT/dP) of the melting curve of diamond at high pressures.
11:00 AM - P4: Growth
BREAK
P5: Doping I
Session Chairs
Tuesday PM, November 27, 2007
Independence W (Sheraton)
11:30 AM - **P5.1
n-Type Diamond Growth by Phosphorus Doping.
Hiromitsu Kato 1 , Toshiharu Makino 1 , Satoshi Yamasaki 1 , Hideyo Okushi 1
1 , AIST, Tsukuba Japan
Show AbstractDiamond is expected to be a promising wide-band-gap semiconductor for electronic and optical applications, such as ultraviolet light emitting diodes (UV-LED), cold cathode electron emitters, and high-power and high-frequency devices. Particularly, exciton-related devices and electron emitters with negative electron affinity are considered to be future applications utilizing the unique properties of diamond. To realize these applications, several fundamental technological issues must be resolved including p- or n-type doping.n-Type diamond is not present in nature, and controlled n-type doping had been considered almost impossible until 1997. Phosphorus, P, has long been considered as a candidate for n-type doping. In 1997, Koizumi et al. experimentally demonstrated the growth of n-type diamond on (111)-oriented diamond substrates by PECVD. However, this discovery of phosphorus doping was closely limited to (111)-oriented diamond lattice structure. For actual technological applications, the growth on (001) substrates is a basic requirement. The (111) diamond surface is difficult to polish mechanically, whereas it is relatively easy to achieve smooth (001) surfaces. In addition, (111)-oriented diamond substrates are difficult to produce, which makes them expensive, and the size is currently limited. To bring diamond electronic applications closer to the actual market, it is necessary to control n-type doping using phosphorus on (001)-oriented crystals.In 2005, we overcame this difficulty by optimizing the conditions for CVD growth, where the parameters differ significantly from those for (111) growth. This is a significant achievement, eliminating the restrictions on crystal orientation of n-type doping. Based on this breakthrough, the fabrication of p-n and p-i-n junctions with good diode characteristics became feasible on (001)-oriented substrate and high-efficiency excitonic emission (~235 nm) at room temperature could be realized. In here, we summarize our research results, including the procedures and conditions of CVD growth, phosphorus incorporation, and characteristic properties and compare it with the features of (111) P-doped diamond. Recent progress in p-i-n junction UV-LED is also reported.
12:00 PM - P5.2
High Temperature Carrier Transport in Phosphorus and Boron Doped Diamond.
Niall Tumilty 1 , Haitao Ye 1 , Mose Bevilacqua 1 , Bertrand Bazin 2 , Milos Nesladek 2 , Philippe Bergonzo 2 , Richard Jackman 1
1 London Centre for Nanotechnology, University College London, London United Kingdom, 2 , CEA-LIST, Saclay, Paris France
Show AbstractIt is now well established that boron and phosphorus can be used to create p-type and n-type diamond respectively. However, both form relatively deep acceptor/donor levels of 0.37 (B) and 0.6eV (P) when present in modest concentrations. This is a problem when devices are fabricated which are designed to operate at room temperature, as most dopants will not be ionised. However, devices which are to be used at elevated temperatures will be unaffected by this issue. Diamond, as a wide band-gap semiconductor (5.5eV), can therefore be considered as an ideal candidate for high temperature electronics.The design of high temperature power electronic devices requires careful correlation of carrier concentrations, compensation ratios and carrier mobility values. Not only must these values be known for the different layers within the device structure at the chosen operating temperature, the influence on temperature fluctuations must also be considered. This paper presents Hall effect measurements carried out over the temperature range 300-800K, for both phosphorus and boron doped epitaxial (111) diamond layers. Surprisingly high carrier mobilities persist even at the highest temperatures measured here.
12:15 PM - P5.3
Compensation and Doping Dependence of the Hall Electron Mobility in Phosphorus Doped {111} Homoepitaxial Diamond.
Julien Pernot 1 , Céline Tavares 1 2 , Satoshi Koizumi 2
1 Nanosciences, University Joseph Fourier and Néel Institute CNRS, Grenoble France, 2 Sensor Materials Center, National Institute for Materials Science, Tsukuba, Ibaraki, Japan
Show AbstractDespite its elevated ionization energy of 570 meV [1], phosphorus (P) is a promising n-type dopant candidate for diamond. P-doped homoepitaxial diamond films have been grown on {111}-oriented substrates and {100}-oriented substrates by microwave plasma-assisted chemical vapour deposition (CVD) using phosphine (PH3) as a dopant source. In order to achieve high performance diamond devices, it is necessary to improve and to control the electrical properties of the P-doped layers. In particular, the scattering mechanisms which limit the free electron mobility must be understood and described in detail.In this work, the Hall mobility of high quality {111} homoepitaxial phosphorus-doped diamond films is systematically compared with theoretical calculations, using a model described elsewhere [2,3]. The temperature dependence (292 K–873 K) of the each scattering modes (phonons and impurities) is described for samples with different P-doping levels. The dependence of the Hall mobility versus the compensation and doping at room temperature is established and discussed.[1] M. Katagiri, J. Isoya, S. Koizumi, and H. Kanda, Appl. Phys. Lett. 85, 6365 (2004).[2] J. Pernot, C. Tavares, E. Gheeraert, E. Bustarret, M. Katagiri and S. Koizumi, Appl. Phys. Lett. 89, 122111 (2006).[3] J. Pernot, W. Zawadzki, S. Contreras, J. L. Robert, E. Neyret, and L. Di Cioccio, J. Appl. Phys. 90, 1869 (2001).
12:30 PM - P5.4
Surface Nano-Morphology and Nanostructures Made of Heavily B-Doped Diamond.
Milos Nesladek 1 , Bohuslav Rezek 2 , Cermak Jan 2
1 CEA - Saclay, LIST, Gif Sur Yvette France, 2 Institute of Physics, Academy of Sciences of the Czech Republic, Prague Czech Republic
Show AbstractNanostructures based on diamond, due to its interesting optical and electrical properties, could be another candidate for UV optoelectronics and biosensing. In general, morphological structures such as nanorods or nanowires have been reported, based on several wide gap semiconducting materials, however diamond nanowires are extremely difficult to prepare due to rather complex gas chemistry during the CVD growth and substrate requirements for homoepitaxy. The growth chemistry during PE CVD growth could be significantly altered by introduction of residual gas impurities, such as dopants, in high concentration and selecting suitable growth conditions for growing single crystal diamond nanostructures. In this work we have investigated morphological changes using high resolution AFM set-up allowing to study the underlined growth mechanism for thin B-doped epitaxial layers prepared on (111) and (100) HPHT substrates using MW–PECVD growth and TMB as a dopant source. We show that at specific conditions unusual morphological structures, resembling nanorods, can be grown, while maintaining their single crystalline character. The KFM measurements were used to study the surface potential profile of the nanostructures grown, showing differences in B-incorporation. The layers have been further studied by Raman measurements, confirming the single-crystal character.
12:45 PM - P5.5
Theory of n-type Doping of Diamond by Deuteration of B-doped Diamond.
Yanfa Yan 1 , Suhuai Wei 1 , Mowafak Al-Jassim 1
1 , National Renewable Energy Laboratory, Golden, Colorado, United States
Show AbstractExperimental results have shown that n-type diamond can be achieved by by deuteration of B-doped diamonds. It is reported that the deuteration of B-doped diamond undergoes two clear steps. The first step is the passivation of B acceptors by deuterium. The second step is the excess deuterium doping that leads to the formation of shallow donors. The experiments suggest strongly that (B,D) complexes are responsible for the shallow donors. Activation energies of 0.2-0.3 eV were found for the donors. Based on density-functional theory calculation, we propose that the experimental data can be explained by doping of impurity-band. Our calculation shows that the passive (B+H) complexes generate fully unoccupied impurity bands, which lie about 1.0 eV below the host CBM. Additional H atoms dope these impurity bands, forming shallow donors. The calculated activation energies are 0.2 and 0.3 eV, agree well with the experimental data. Based on this concept, other acceptor-donor complexes will also be discussed.
P6: Detectors I
Session Chairs
Tuesday PM, November 27, 2007
Independence W (Sheraton)
3:00 PM - **P6.1
Probing The Transient Response To Improve The Stability Of Diamond Devices Under Pulsed Periodic Excitation.
P. Bergonzo 1 , H. Hamrita 1 , D. Tromson 1 , C. Descamps 1 , C. Mer 1 , M. Nesladek 1
1 , CEA LIST, Gif sur Yvette France
Show AbstractCVD diamond combines attractive properties for the fabrication of detection devices operating in specific environments. One inherent problem however with diamond is the presence of defect levels that are altering the detection characteristics. These are observed in most CVD materials just like they were observed in very high quality natural diamonds. They result in unstable responses and carrier losses. Also, it is known that unstable observed sensitivities may result from the progressive filling of trapping levels (including e.g. pumping and polarisation effects), with a detrimental effect on stability and response time. Several studies have aimed at identifying the origin of defect levels but the question remains open : impurities, dislocations, and grain boundaries are often associated with the presence of electrical defects. The defect levels associated with such trapping states are spreading from shallow to deep traps, and thus their populations are also strongly affected by the temperatures at which the device is used. The challenge has been to grow materials with the least defect concentrations: single crystals are foreseen as good candidates but still the presence of defects can always be probed, probably from propagating dislocations and low impurity concentrations (B, N etc). We had tried to optimise other routes that are based on the temperature control of the devices either during use, or between uses. This implies the detrapping of electrical species using thermal excitation, but of course requires the fine control of the device temperature, together implying limits for the domains of applications: e.g. a tissue equivalent diamond detector is an interesting material for dose metrology in radiotherapy applications, but when kept at typ. 100°C it clearly looses part of its interests and namely its bio-inertness…One of the issues discussed here will analyse the situation when the devices are operated in the pulsed mode regime, i.e. when transitory effects are less impacted by defective level evolution than for steady state currents. This comes as a very valuable route to improve the device performance when used for monitoring pulsed radiation sources (e.g. medical accelerators) in terms of linearity and reproducibility. Also, it implies the use of materials that are faster, but also of lower carrier lifetime, and therefore generally agreed to be of poorer quality. This has therefore to be compromised with respect to the desired performances.
3:30 PM - P6.2
Single Crystal CVD Diamond Detectors: Position and Temporal Response Measurements using a Synchrotron Microbeam Probe.
John Morse 1 , Murielle Salome 1 , Eleni Berdermann 2 , Michal Pomorski 2 , Petr Ilinski 3
1 Experiments Division, ESRF, Grenoble France, 2 Detektorlabor, Gesellschaft für Schwerionenforschung, Darmstadt Germany, 3 Hasylab, DESY, Hamburg Germany
Show Abstract3:45 PM - P6.3
Development of Fast CVD Diamond Detectors for Inertial Confinement Fusion Experiments.
Vladimir Glebov 1 , Thomas Sangster 1 , Christian Stoeckl 1 , Sam Roberts 1 , Chad Mileham 1 , Oliver Landoas 2 , Laurent Disdier 2 , Philippe Bergonzo 3 , Hassen Hamrita 3
1 , Laboratory for Laser Energetics, University of Rochester, Rochester, New York, United States, 2 , CEA/DIF, Bruyeres-le-Chatel France, 3 , CEA/Saclay, Gif-sur-Yvette France
Show AbstractNeutron time-of-flight detectors based on chemical vapor deposition (CVD) diamonds in current-mode have been sucsessfully operated in inertial confinement fusion (ICF) experiments. Experiments on the future National Ignition Facility (NIF) and Laser Mega Joule (LMJ), currently under construction in USA and France, will produce up to 2 E19 neutrons. The NIF and LMJ facilities will require fast CVD diamond detectors with a wide range of sensitivities. Studies of the sensitivity and time response of different CVD diamonds were performed with a fast electron beam on ELSA facility in France and with DT neutrons on the 60-beam, 30 kJ OMEGA laser facility in the USA. Results of these studies and proposed CVD diamind detectors for the NIF and LMJ will be presented.This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under the Cooperative Agreement No. DE-FC52-92SF19460.
4:00 PM - P6.4
Development of a Hydrogen Termination Procedure for Tetrahedral Amorphous Carbon for use with the Interstellar Boundary Explorer.
Joshua Smith 1 , Robert Nemanich 2 , Eric Hertzberg 3 , Thomas Friedmann 4
1 Department of Physics, North Carolina State University, Raleigh, North Carolina, United States, 2 Department of Physics, Arizona State University, Tempe, Arizona, United States, 3 Advanced Technology Center, Lockheed Martin, Palo Alto, California, United States, 4 , Sandia National Laboratories, Albuquerque, New Mexico, United States
Show AbstractThe interstellar boundary explorer, IBEX, is an orbiting satellite that detects neutral particles in space and features a tetrahedral amorphous carbon (ta:C) conversion surface. Neutral particles enter the IBEX-Lo detector and strike the ta:C conversion surface where they are ionized. The particles are then detected by a time of flight mass-energy spectrometer. Hydrogen termination improves the ionization efficiency of the ta:C facets. Additionally, the project required an RMS roughness of less than 0.1nm over a 1x1 μm2 area to ensure specular reflection of particles and thus improve detection efficiency. 100nm of ta:C was deposited on Si by pulsed laser deposition at Sandia National Lab. A procedure was developed at North Carolina State to H-terminate the facets by exposure for two minutes to a remote hydrogen plasma in an ECR-CVD vacuum system. X-ray photoemission spectroscopy was performed before and after H-termination and showed removal of oxygen from the surface by the CVD procedure. Ultraviolet photoemission spectroscopy was performed before and after H-termination and showed a decrease in the vacuum cutoff after the treatment as well as a sharp peak in the spectrum at the vacuum cutoff, indicating a negative electron affinity and suggesting the presence of hydrogen. AFM was performed before and after the termination procedure and it was found that the facets were not roughened above the project specification.The ECR CVD technique was chosen specifically to maintain the very low RMS roughness of the ta:C surface. The plasma was maintained by flowing 20sccm of hydrogen into the chamber while delivering 300W of microwave power. The plasma was contained between the two ECR magnets; the top magnet was operated with 105A of current and the bottom with 118A. The ECR system is configured such that the plasma is maintained at a distance of around 0.5m below the facet surface. Therefore, the surface was not directly exposed to the high temperatures and energetic ionic species of the plasma and thus avoided possible damage.This project was supported by a grant through Lockheed Martin.Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000
Symposium Organizers
Richard B. Jackman University College London
Christoph Nebel National Institute of Advanced Industrial Science and Technology
Robert J. Nemanich Arizona State University
Milos Nesladek Commissariat Energie Atomique (CEA/Saclay)
P7: Biotechnology II and Carbon Devices
Session Chairs
Wednesday AM, November 28, 2007
Independence W (Sheraton)
9:30 AM - **P7.1
Chemical Modification of Carbon Materials with Sulfur Functionalities.
T. Nakamura 1
1 , National Institute of Advanced Science and Technology, Tsukuba Japan
Show Abstract10:00 AM - P7.2
Microscopic Detection of DNA Hybridization using Miniaturized Diamond DNA-FETs.
Christoph Nebel 1 , Nianjun Yang 1 , Hiroshi Uetsuka 1 , Hideyuki Watanabe 1 , Takatoshi Yamada 1 , Takako Nakamura 2
1 AIST, Diamond Research Center, Tsukuba, 0, Japan, 2 Center for Advanced Carbon Materials, AIST, Tsukuba, Ibaraki, Japan
Show AbstractBio-sensors from diamond attract increasing attention, as they are promising with respect to chemical properties, show strong bonding to bio-molecules and offer a variety of detection schemes like cyclic voltammetry, impedance spectroscopy and gate threshold potential variations in bio-functionalized ion-sensitive field effect transistor structures (ISFET). The in-plane gate structure of ISFETs from diamond are unique, as they are based on a thin surface conductive layer in close vicinity to the buffer solution. Unfortunately, such devices from diamond show mostly strong variations in sensor quality, stability and reproducibility. To elucidate the reasons for these features, we have manufactured a set of bio-functionalized diamond ISFETs, with active sensor areas varying between hundreds of square micrometers down to small areas, typically in the micrometer regime. Such structures are manufactured on atomically smooth surfaces which allow the application of AFM/STM experiments to characterize the homogeneity of the bio-layers attached on the gate in conjunction with transistor characterization techniques, where the drain source currents are measured as a function of gate potentials, iconicity of the used buffer solutions and of the DNA hybridization.The results will be discussed, taking into account the AFM/STM data, ISFET sensitivity, stability and reproducibility to establish a reliable set of data for such devices to be used in multi-array DNA sensor structures for cancer detection.
10:15 AM - P7.3
Electrochemical-STM Analysis on Bio-functionalized Diamond Surfaces.
Hiroshi Uetsuka 1 , Nianjun Yang 1 , Hideyuki Watanabe 1 , Norio Tokuda 2 , Christoph Nebel 1
1 Diamond Research Center, National Institute of Advanced Industrial science and Technology, Tsukuba Japan, 2 Nanotechnology Research Institute, National Institute of Advanced Industrial science and Technology, Tsukuba Japan
Show AbstractDiamond bio-sensors attract increasing attention as diamond is promising with respect to biocompatibility, chemical inertness, and electrochemical properties. Many results about sensitivities with respect to pH, DNA, enzymes and proteins activities have been reported already, using nano-, poly- and single-crystalline diamond as transducers [1]. These materials show however a great variety with respect to surface properties, grain boundaries and grains, sp2/sp3 ratios and boron doping homogeneity. Macroscopically detected sensitivities will therefore be dominated by a variety of microscopic inhomogeneities. Up-to now however, no microscopic discussion and characterization of bio-sensors from diamond have been presented. In the study, we introduce electrochemical-scanning tunneling microscopy (EC-STM) data deduced from measurements on metallically boron doped poly- and single-crystalline CVD diamonds, on linker (amine and phenyl) modified diamonds and on DNA grafted diamond biosensors, in biological buffer solution. These films are atomically smooth, and H-terminated before bio-functionalization. Nitrophenyl [2] and amine layers [3] are prepared by electrochemical and photochemical techniques, DNA is bonded to such films as described in Ref. 1. The EC-STM data show strong local variations of linker molecule densities on diamond, which are also seen after DNA attachment. The macroscopic electrochemical signal is strongly affected by the number of pin-holes in such films. The results will be discussed in detail, taking into account surface smoothness, grain boundaries and H-termination effects.[1] C.E. Nebel et al., J. R. Soc. Interface 4 (2007) 439.[2] H. Uetsuka et al., Langmuir 23 (2007) 3466.[3] N. Yang et al., Chem. Mater. 19 (2007) 2852.
10:30 AM - **P7.4
Flat Carbon Substrates for Molecular Electronics: toward Molecular Memory Devices.
Richard McCreery 1 2 , Jing Wu 2 , Haijun Yan 2 , Andrew Bonifas 2 , Sudip Barman 2
1 Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada, 2 , National Institute of Nanotechnology, Edmonton, Alberta, Canada
Show AbstractPyrolysis of commercial photoresist in a reducing atmosphere yields extremely flat sp2 hybridized carbon films, which may be patterned with photolithography1-3. Covalent bonding of organic molecules to these films yields a C-C bond stable to > 500 oC, and permits fabrication of carbon/molecule/metal molecular electronic junctions. We use Raman, FTIR, and UV-Vis spectroscopy to probe the structure of the molecules in live molecular junctions, in which molecules are subjected to unusually large electric fields (e.g. 107 V/cm)4-6. The behavior of molecules as circuit components is strongly dependent on temperature, molecular structure and bonding to the contacts, and it is possible to monitor chemical changes in molecular junctions during operation. Of particular interest are bistable memory devices containing both a molecular layer and a metal oxide, which exhibit excellent persistence (> 24 hours) and fast read/write/erase times (~ 10 μsec).(1) Wu, J.; Mobley, K.; McCreery, R.; Electronic characteristics of fluorene/TiO2 molecular heterojunctions; J. Chem. Phys. 2007, 126, 24704.(2) McCreery, R.; Wu, J.; Kalakodimi, R. J.; Electron Transport and Redox Reactions in Carbon Based Molecular Electronic Junctions; Phys. Chem. Chem. Physics. 2006, 8, 2572.(3) Ranganathan, S.; McCreery, R. L.; Majji, S. M.; Madou, M.; Photoresist-Derived Carbon for Microelectrochemical Applications; J. Electrochem. Soc. 2000, 147, 277.(4) Nowak, A.; McCreery, R.; In-Situ Raman Spectroscopy of Bias-Induced Structural Changes in Nitroazobenzene Molecular Electronic Junctions; J. Am. Chem. Soc. 2004, 126, 16621.(5) Kalakodimi, R. P.; Nowak, A.; McCreery, R. L.; Carbon/Molecule/Metal and Carbon/Molecule/Metal Oxide Molecular Electronic Junctions; Chem. Mater 2005, 17, 4939.(6) McCreery, R. L.; Analytical challenges in molecular electronics; Analytical Chemistry 2006, 78, 3490.
11:00 AM - P7: Biotech II
BREAK
P8: Industrial Perspectives
Session Chairs
Wednesday PM, November 28, 2007
Independence W (Sheraton)
11:30 AM - **P8.1
Using Diamond to Enhance Competitive Wide Bandgap Technologies.
Jerry Zimmer 1
1 , sp3 Diamond Technologies, Santa Clara, California, United States
Show AbstractIntegrating diamond heat spreaders into the junction region of high power wide bandgap compound semiconductor devices offers a competitive parallel path to achieving some of diamond’s promise as a wide bandgap electronic material without the high risk factors of developing a brand new material and device architecture. The concept is to place diamond as close as possible to the heat generating area of a high quality wide bandgap semiconductor. This paper will discuss some of the recent progress being made in combining efficient diamond heat spreading layers with wide bandgap materials such as GaN. Prototype device results will be presented which show both the promise and the problems of such an architecture.
12:00 PM - **P8.2
The New Diamond Age.
Robert Linares 1
1 , Apollo Diamond, Framingham, Massachusetts, United States
Show AbstractThe "New Diamond age" was ushered in during the 1950's with invention of the high temperature-high pressure process for synthesis of diamond. This was quickly followed by processes to form large polycrystalline diamond (PCD) compacts. Together, these new diamond products revolutionized the materials fabrication industries which led to new applications for diamond and exponential growth of diamond production. In the mid 1980's CVD grown diamond was introduced and polycrystalline products, as bulk and thin film, began to find their way into large scale use. Now, in the 2000's, CVD grown single crystal diamond has become available in large sizes and controlled properties. The wide availability of CVD grown single crystals will bring about a new era of dramatic growth in the diamond industry. The application of the various forms of diamond and trends for the future will be discussed.
12:30 PM - **P8.3
Recent Progress In Delta-Doped Diamond MESFET Technology.
Richard Lang 1
1 , Diamond Microwave Devices Ltd, County Durham Ireland
Show AbstractP9: Emission Devices
Session Chairs
Wednesday PM, November 28, 2007
Independence W (Sheraton)
2:30 PM - P9.1
Novel Approaches to Moderate Temperature Thermionic Emitters Based on Nitrogen – Doped Diamond Thin Film Stacks.
Franz Koeck 1 , Robert Nemanich 2
1 Physics, NC State University, Raleigh, North Carolina, United States, 2 Physics, Arizona State University, Tempe, Arizona, United States
Show AbstractEfficient, high brightness electron sources are crucial for a wide variety of applications from high power microwave sources for communications to space propulsion systems. While the electron extraction mechanism can vary (field and thermionic emission), the energy needed to remove electrons from an emitter is directly related to the emission barrier, i.e. the effective work function, where low values of the effective work function correspond to higher emission currents at a given temperature. We have employed microwave plasma assisted CVD to prepare a stacked layer thermionic emitter comprised of a metallic substrate, nucleation– and a doped diamond layer. Crucial to the emission characteristics are substrate material and a highly conductive nucleation layer for the nitrogen doped diamond thin film. Employing a nitrogen – incorporated nucleation layer grown with Ar in the gas feed resulted in detectable electron emission at temperatures < 250 °C. This low resistivity layer can provide efficient electron injection into the successive highly nitrogen doped diamond film which exhibits a negative electron affinity (NEA) surface due to the exposure of the film surface to a hydrogen plasma. An evaluation of the emitter structure with respect to the thermionic emission law of Richardson – Dushman provided a work function < 1.4 eV with a Richardson’s constant AR > 1 A/cm2.
This research was supported by the Office of Naval Research through the TEC MURI.
2:45 PM - P9.2
Diamond Amplified Photocathodes.
John Smedley 1 , Ilan Ben-Zvi 1 , Andrew Burrill 1 , Xiangyun Chang 1 , Ranjan Grover 1 , Abdel Isakovic 1 , Triveni Rao 1 , Qiong Wu 2
1 , Brookhaven National Laboratory, Upton, New York, United States, 2 , Indiana University, Bloomington, Indiana, United States
Show AbstractHigh-average-current electron linacs require photo-injectors capable of delivering tens to hundreds of mA average current, with peak currents of hundreds of amps. Standard photocathodes face significant challenges in meeting these requirements, and often have short operational lifetimes in an accelerator environment. We report on recent progress toward development of secondary emission amplifiers for photocathodes, which are intended to increase the achievable average current while protecting the cathode from the accelerator. The amplifier is a thin diamond wafer, which converts energetic (few keV) primary electrons into hundreds of electron-hole pairs. The electrons drift through the diamond under an external bias and are emitted into vacuum via a hydrogen-terminated surface with negative electron affinity (NEA). Secondary emission gain of over 300 has been achieved for both single crystal and polycrystalline CVD diamonds. Techniques of diamond preparation, including metallization and hydrogen termination, have been adapted to this application. Two methods of patterning diamond, laser ablation and reactive-ion etching, are being developed to produce the required geometry. A variety of diagnostic techniques, including FTIRS, SEM and AFM, have been used to characterize the diamonds.
3:00 PM - **P9.3
Diamond Cold Discharge Cathodes for Backlight Lamp Application.
Tadashi Sakai 1 , Tomio Ono 1 , Naoshi Sakuma 1 , Mariko Suzuki 1 , Daisuke Takeuchi 2 , Satoshi Yamasaki 2 , Shozo Kono 3
1 Corporate R. & D. Center, Toshiba Corporation, Kawasaki, Kanagawa, Japan, 2 , AIST, Tsukuba, Ibaraki, Japan, 3 , Tohoku University, Sendai, Miyagi, Japan
Show AbstractBoron (B)-doped polycrystalline diamond has been investigated as a cold discharge cathode material. Cathode fall voltage of diamond has shown at a minimum 1/3 of that of a conventional cathode material such as Mo. A grow-discharge tube with a cold cathode fluorescent lamp (CCFL)-like slim outer shape has been demonstrated applying a diamond cathode.CCFLs are now widely used as backlights for liquid crystal displays. Due to their simple structures, features necessary for the backlight application are available, namely, long lifetime and slim tubular shape. However, luminous efficiency of CCFLs is lower than that of hot cathode type fluorescent lamps. One of the reasons of the loss is a large cathode fall (Vc) of cold discharge cathodes. Therefore, we have proposed B-doped polycrystalline diamond as a cathode material to reduce this large Vc (1). In this contribution, CVD conditions of the B-doped diamond films have been varied to clarify relationship between the film characteristics and Vc. The results obtained indicate that the Vc is strongly related to both ion-induced secondary electron efficiency and photo-induced electron yield. The lowest Vc observed among the films was less than 50 V, which was almost 1/3 that of a conventional Mo cathode.The B-dope diamond film was coated on a small Mo cathode substrate (1.7 mmΦ) and implemented in a slim tubular shape discharge tube. The diamond cathode tube shows proper glow discharge on the cathode head in the current range less than 1 mA. Although the discharge current is still smaller than that of a commercialized CCFL, the driving voltage of the diamond cathode tube is more than 10% smaller than that of an uncoated Mo cathode tube.1. T. Sakai, T. Ono, N. Sakuma, M. Suzuki, and H. Yoshida, Abst. of 16th European Conference on Diamond, Diamond-Like Materials, Carbon Nanotubes, Nitrides & Silicon Carbide, (2005) 16.1.This work was supported by the ADD project funded by the NEDO of Japan.
3:30 PM - P9.4
Phosphorus Doped Diamond Electron Emitter Devices.
Natsuo Tatsumi 1 , Akihiko Ueda 1 , Keisuke Tanizaki 1 , Yoshiki Nishibayashi 1 , Takahiro Imai 1
1 , Sumitomo Electric Industries, LTD, Itami, Hyogo, Japan
Show AbstractDiamond is expected to be one of the best material of electron emission devices due to the outstanding physical properties such as negative or low electron affinity. Many researchers made much efforts to study surface and electron emission properties in 1990's and various undoped and boron doped diamond electron emitters were reported. As doping technology developed, n-type diamonds were found to have high electron emission properties. We are convinced that the n-type diamond electron emission devices are the next generation electron sources.However, device fabrication on n-type phosphorus doped diamond had 2 difficulties. First, large substrate were necessary for fabricating homogeneous 3 dimensional device structure. Highly doped diamond layer can be grown only on (111) diamond substrate. Because large (111) diamond substrate is not available, an enlargement approach of substrate size was needed. Second problem was that the resistivity of n-type diamond was still over 100 Ohm cm and too high for high current electron emission devices.To solve these problems, we developed a new large size composite wafer in which (111) single crystal diamond was buried in polycrystal diamond and highly homogeneous electron emitter devices were successfully fabricated. And we also developed a new electrode coated emitter tip structure for conduction support only whose apex was exposed from the electrode.N-type phosphorus doped diamond was grown on the 15 mm composite diamond wafer with high PH3/CH4 concentration of 20% and high doped active layer was epitaxially grown on the embedded (111) single crystal. Sharp emitter tip arrays were fabricated by etching the n-type diamond. The radius of the apex was as small as 2 nm. Electrodes were coated on these tips and exposed area of diamond was less than 200 nm from the apex of the tip. Gate electrodes were also fabricated for each emitter tips. A boron doped diamond device was fabricated for comparison of the electron emission properties.Electron emission of these devices were measured in the vacuum of 10-7 Pa. The threshold voltage of the n-type diamond device was 60 V which was lower than 100 V of the p-type diamond device. The threshold voltage of n-type diamond with and without electrode coatings did not changed. This means that electrode coating did not affect the emission properties and electrons were emitted from the diamond surface. The emission current was enhanced by 2 orders by the electrode coatings and total emission current from 1 mm2 reached 1103 mA. This high emission current electron source enables applications to microwave tubes, electron beam processing and integrated micro vacuum devices.
3:45 PM - P9.5
Electron Emission from Diamond pn Junction.
Satoshi Koizumi 1 , Mariko Suzuki 2 , Tadashi Sakai 2
1 Sensor Materials Center, National Institute for Materials Science, Tsukuba Japan, 2 Corporate Research and Development Center, Toshiba Corporation, Kawasaki Japan
Show AbstractIt is well known that p-type diamond surface shows negative electron affinity (NEA) state. If we could inject electrons on the conduction band of p-type diamond and transport to the surface, we will have a high efficiency electron emitter that is insensitive to operating environment (range and quality of vacuum etc.). As we have already reported, diamond pn junction shows clear diode characteristics and ultraviolet light emission under forward bias operation. This shows the injection of minority carriers is taking place at pn junction interface. In the present study, we formed diamond pn junctions with different thickness of p-type layers and examined the electron emission measurement in vacuum. The phosphorus doped n-type diamond films are formed on {111} Ib diamond surface by microwave plasma chemical vapour deposition with the thickness of n-type 5-10 μm. The p-type boron doped layers have been formed on the n-type layers by CVD with the thickness variation of 250 nm, 500 nm and 1 μm. The pn junctions were processed by reactive ion etching using oxygen to form mesa structures (250 μmΦ). The electron emission measurements were performed in ultra high vacuum probe testing system. Electron emission was observed with forward bias operation of diodes. When the pn junction shows poor rectification characteristics by current leakage, the electron emission has not been observed. At room temperature, the emission current was the order of nA because high resistance of n-type layer suppress the diode current to the order of μA. When the sample was heated to 300 C, we could have 30 μA of emission current from a single mesa of 250 nm sample at diode current of 5 mA, corrector voltage 100 V. The maximum electron emission efficiency was 0.64 %. This value is very large as to a preliminary device having a simple mesa structure with a plane circular metal contact. The corrector voltage dependence of emission current showed clear onset at around Vc=0 V that implies the successful formation of NEA emitter.
4:00 PM - P9: Em. Devices
BREAK
P10: Detectors II
Session Chairs
Wednesday PM, November 28, 2007
Independence W (Sheraton)
4:30 PM - **P10.1
CVD Diamond for Accelerating and Detecting High Energy Particles.
Roy Gat 1 , Alexei Kanareykin 3 , Paul Schoessow 3 , Harris Kagan 2
1 , Coating Technology Solutions Inc, Somerville, Massachusetts, United States, 3 , Euclid Labs, Rockville, Maryland, United States, 2 Physics Dept, Ohio State Univ, Columbus, Ohio, United States
Show AbstractCVD diamond tubes were developed and applied to dielectrically loaded accelerator structures (DLA). DLA is one of the most promising technologies for advanced accelerators expected to sustain accelerating gradient in excess of 100 MV/m. DLA'a can be applied in the linear collider and medical accelerators for cancer therapy. High quality polycrystalline diamond was used for detection of high energy ionizing radiation. Collection distance scales with film thickness. Best results showed collection distance of the order of 20% of the film thickness enabling applications in fundamental high energy physics and in medical dosimetry.
5:00 PM - P10.2
Synthetic Single Crystal Diamonds as Radiotherapic Dosimeters.
Isabella Ciancaglioni 4 , Rita Consorti 2 , Francesco De Notaristefani 3 , Marco Marinelli 1 , Enrico Milani 1 , Assunta Petrucci 2 , Aldo Tucciarone 1 , Gianluca Verona-Rinati 1
4 Ingegneria Elettronica, Università ``Roma 3", Roma Italy, 2 U.O. Fisica Sanitaria, Ospedale S. Filippo Neri, Roma Italy, 3 INFN - Sez. Roma 3, Università ``Roma 3", Roma Italy, 1 Ingegneria Meccanica, Università ``Tor Vergata", Roma Italy
Show Abstract5:15 PM - P10.3
Single Crystal CVD Diamond Growth for Detection Device Fabrication.
Tranchant Nicolas 1 , Tromson Dominique 1 , Hamrita Hassen 1 , Moignau Fabien 1 , Nesladek Milos 1 , Bergonzo Philippe 1
1 DRT / LIST DETECS / SSTM / LTD, CEA - LIST, Gif - Sur Yvette France
Show Abstract5:30 PM - P10.4
Performances of Epitaxial Diamond in the Field of X-ray Tube Diagnostics.
Claudio Manfredotti 1 , Lorenzo Visca 1 , Alessandro Lo Giudice 1
1 , University of Torino, Torino Italy
Show AbstractCarefully selected natural diamond dosimeters are presently used in the field of X-ray radiotherapy. Recently (1, 2 ) we reported on the performances of epitaxial CVD diamond as radiological X-ray dosimeter for energies up to 120 KeV and on a comparison with silicon : current pulse shapes generated by X-rays were integrated and the obtained charge was compared with dose measured by standard ionization chambers. Linearity tests with respect the measured doses were carried out. Results were encouraging, but diamond dosimeters were not optimized, particularly as far as electrodes were concerned. The present work is carried out with a better defined electrode geometry and with CVD diamond detectors reaching 100% charge collection efficiency at reasonable bias voltages. of the order of few V/micrometer. As before, no previous priming is necessary. Dose linearity is perfect for doses from 5 up to 120 mGy, as obtained with maximum X-ray energies from 50 to 120 KeV and for time-anodic current products from 20 up to 100 mAs. Reproducibility, which includes both fluctuations of generated X-ray pulses at given mAs and of dose recorded by ionization chamber, is very good. Pulse timimg, which is given both by the X-ray generator and by a standard diagnostic monitor based on a filtered silicon detectors array, is reconstructed with a time resolution better than 10 ms. The response of the dosimeter is constantly 8 10-8 C/Gy, which corresponds in our case to 0.43 C/J. In conclusion, CVD epitaxial diamond dosimeter can be very suitably used as a unique diagnostic tool in order to measure the entrance dose at the patient level, to display tube efficiency curves in terms of delivered Gy’s as a function of selected mAs and finally to compare the real timing of X-ray pulses with time setting in terms of mAs. All these functions, which are commonly carried out by different devices, may be now gathered in only one, which is able to give a tissue-equivalent dose. By a standard X-ray filter set, as done in common silicon detector arrays, the same CVD diamond dosimeter may give also the maximum or the effective X-ray energy, by completing this way the X-ray tube diagnostics procedure.1) Y. Garino, A. Lo Giudice, C. Manfredotti, Marco Marinelli, E. Milani, A. Tucciarone and G. Verona-Rinati “ Performances of homoepitaxial single crystal CVD diamond in diagnostic X- Ray dosimetry”, Applied Physics Letters 88 (2006) 1519012) A. Balducci, Y. Garino, A. Lo Giudice, C. Manfredotti, Marco Marinelli, G. Pucella and G. Verona-Rinati “ Radiological X-ray dosimetry with single crystal CVD diamond detectors” Diamond and Related Materials 15 (2006) 797-801
5:45 PM - P10.5
Developments of New Single Crystal Diamond Detectors : Applications in Radiotherapy.
Dominique Tromson 1 , Nicolas Tranchant 1 , Caroline Descamps 1 , Aurelie Isambert 2 , Milos Nesladek 1 , Philippe Bergonzo 1
1 , CEA-LIST, Gif sur Yvette France, 2 , IGR, Villejuif France
Show AbstractTreatment of cancers is of great importance at the beginning of this century. Several European projects are focusing on this topic. The MAESTRO (Methods and Advanced Equipment for Simulation and Treatment in Radio-Oncology, 6th FP)project aims to develop the tools for measurements of radiation and simulation equipment for radiotherapy. One of the innovative tools is the single crystal diamond detector for measurements of new fields of irradiation as for example in the case of IMRT (Intensity Modulated Radiation Therapy).Diamond exhibits attractive properties for applications in the medical field as soft-tissue equivalence (Z=6 compared to Z=7.42 for human tissue), mechanical robustness and radiation hardness. One of the particular interesting properties of diamond is the small volume of detection due to the high sensitivity of the material that allows its use for IMRT treatments. This technique will be developed in many clinics and hospitals in the future for a better control and adjustment of the dose received by the tumour and until now there is no other detector than diamond that are well adapted to these kinds of measurements. Detectors fabricated from natural diamonds are used in several hospitals but these devices are expensive with long delivery times are common. The use of synthetic single crystal diamond is a promising issue for point dosimeter in IMRT fields.Here we report on the growth of synthetic diamond using the CVD technique to fabricate single crystals. Samples were characterized (Raman, TOF…) and mounted as solid state ionisation chambers in a special holder for the evaluation of their dosimetric properties. The dosimetric performances of synthetic single crystal detectors were evaluated in medical conditions in specialised Institutes in the treatment of tumours. Results were estimated with respect to the requirements of the Code of practice IAEA (International Atomic Energy Agency) TRS-398. Response time, stability and repeatability of the signal, signal to noise ratio, linearity with the absorbed dose, dose rate and energy dependence were evaluated. A good agreement is shown between the results and the requirements tested that demonstrate the quality of such single crystal diamond detectors for radiotherapy applications.
Symposium Organizers
Richard B. Jackman University College London
Christoph Nebel National Institute of Advanced Industrial Science and Technology
Robert J. Nemanich Arizona State University
Milos Nesladek Commissariat Energie Atomique (CEA/Saclay)
P11: Nanocrystalline Diamond
Session Chairs
Thursday AM, November 29, 2007
Independence W (Sheraton)
9:45 AM - **P11.1
Configuration Interactions and the Mechanism of n-type Conductivity in Ultrananocrystalline Diamond.
Dieter Gruen 1
1 Materials Science Division, Argonne National Laboratory, Argonne, IL, Illinois, United States
Show AbstractIn recent work, the origin of the n-type metal-insulator transition in ultrananocrystalline diamond (UNCD) has been shown to be strongly correlated with a nanostructural transformation resulting in partially oriented diamond nanowires surrounded by an sp2 bonded carbon sheath when nitrogen is added to the synthesis gas (1). The plasma conditions prevailing during UNCD deposition are known to be conducive to the formation of precursor species for polymers such as polyacetylene, polynitrile and cyanopolyynes (2). Based on detailed density functional calculations (3) highly exothermic cycloaddition reactions of conjugated hydrocarbon molecules such as these with the partially sp2 bonded carbon dimers of the reconstructed (100) surface likely occur resulting in thermally stable conducting “graphitic” chains of carbon atoms covalently bonded to diamond. These initial nucleation sites provide the growth centers that develop into the sp2 bonded carbon sheaths observed in HRTEM and EELS measurements (1) along which facile electron transport can occur. The thermal stability of these nanostructured composites make them of interest for a number of high temperature applications.Carbon is unique in having allotropes, diamond and graphite, whose physical and chemical properties are widely divergent while their free energies of formation differ by only 0.02ev. Electron delocalization leading to electronic conductivity is strongly dependent on sp3/sp2 hybridization ratios. Control of this parameter will be discussed from the point of view of the relationship between the energetics and the size, structure and bonding configuration of nanocarbons.(1)R. Arenal, P. Bruno, D. J. Miller, M. Bleuel, J. Lal and D. M. Gruen, Phys. Rev. B 75, 195431 (2007).(2)F. Cataldo, Editor –in-Chief, Polyynes: Synthesis, Properties, and Applications, CRC (2005).(3)D. R. Fitzgerald and D. J. Doren, J.A.C.S., 122, 12334 (2000).This work was supported by the U. S. Department of Energy, Office of Science, under Contract DE-AC02-06CH11357.
10:15 AM - P11.2
Reaction of Conjugated Hydrocarbons with Diamond.
Paola Bruno 1 , Dieter Gruen 1 , Markus Bleuel 2 , Jyotsana Lal 2
1 MSD, Argonne National Laboratory, Argonne, Illinois, United States, 2 , Pulsed Neutron Source, Argonne National Laboratory , Argonne, Illinois, United States
Show AbstractIn ultrananocrystalline diamond (UNCD) film growth, the synthesis of crystallites and grain boundaries are simultaneous events. In recent work, the importance of the grain boundaries in determining the remarkable ambient temperature conductivity of n-type UNCD has been discussed in detail (1). It has become a matter of considerable interest to study in detail the mechanism of formation of the grain boundaries in these nanomaterials so as to be able to optimize their electronic transport properties.We have chosen disperse UNCD powder (DUNCD) with a crystallite size distribution virtually identical to that in UNCD films as a starting material. After an initial densification step, the compacts having an approximate density of unity are exposed to flowing methane or methane/nitrogen gas mixtures and heated in a tube furnace to temperatures of 300-1200K. Weight gain is observed and measured as a function of temperature and time.The results are interpreted on the basis of Raman data, X-Ray diffraction results and Small Angle Neutron Scattering (SANS) measurements. In brief, the material deposited as a result of methane exposure is “graphitic” in nature and electrically conducting thus displaying two of the outstanding characteristic of the UNCD film grain boundaries. The XRD measurements confirm that the amount of diamond component of the composite remains invariant during the reaction cycle. The SANS results will be discussed on the basis of changes in the size and shape of the agglomerates that occur during the reaction cycle.At the temperatures where “graphitic” carbon deposition occurs, it is likely that decomposition of methane to conjugated hydrocarbon occurs which can react with the sp2 bonded dimers of the diamond (100) surface leading to polymer-like structures, reminiscent of the nature of the film grain boundaries. The current approach appears to be a fruitful one for the investigation of the sequential formation of “grain” boundary-like material in the nanoporous DUNCD matrix.(1) R. Arenal. P. Bruno, D.J. Miller, M. Bleuel, J. Lal, D.M. Gruen, “Diamond nanowires and the insulator-metal transition in Ultrananocrystalline Diamond films”. Phys. Rev. B. 75, 19, 195431 (2007).This work was supported by the U. S. Department of Energy, Office of Science, under Contract DE-AC02-06CH11357.
10:30 AM - **P11.3
Nanodiamond Powders: Oxidation, Surface Functionalization and Phonon Confinement.
Yury Gogotsi 1 , V. Mochalin 1 , S. Osswald 1 , C. Portet 1 , M. Havel 1 , C. Hobson 1
1 , Drexel University, Philadelphia, Pennsylvania, United States
Show AbstractThursday, November 29New Presenter - *P11.3Nanodiamond Powders: Oxidation, Surface Functionalization and Phonon Confinement. Vadym Mochalin
11:00 AM - P11: NCD
BREAK
P12: Quantum Information Processing
Session Chairs
Thursday PM, November 29, 2007
Independence W (Sheraton)
11:30 AM - **P12.1
Defect in Diamond: Application in Quantum Optics and Imaging.
Joerg Wrachtrup 0
0 , University of Stuttgart, Stuttgart Germany
Show AbstractThe optical properties of defects in diamond are outstanding among all solid state quantum systems. Some defect show strong optical transitions coupled to electron paramagnetic states. This makes them ideally suited for certain applicaitons in quantum information processing. On the other hand the high photostability of e.g. the nitrogen-vacancy color center makes it an ideal point-like light emitter for high resolution microscopy. The talk will highlight recent developements.
12:00 PM - P12.2
Triggered Single-photon Source based on Photoluminescence of Nickel-related Colour Centres in CVD-grown Nanodiamonds
Francois Treussart 1 , E. Wu 1 2 , Vincent Jacques 1 , James Rabeau 4 , Heping Zeng 2 , Steven Prawer 4 , Philippe Grangier 3 , Jean-Francois Roch 1
1 Laboratoire de Photonique Quantique et Moleculaire, Ecole Normale Superieure de Cachan, Cachan France, 2 Key Laboratory of Optical and Magnetic Resonance Spectroscopy, East China Normal University, Shanghai China, 4 School of Physics, University of Melbourne, Melbourne, Victoria, Australia, 3 Laboratoire Charles Fabry de l’Institut d’Optique, Institut d'Optique Graduate School, Palaiseau France
Show AbstractDue to its fascinating luminescence properties, e.g. its near perfect room temperature photostability, the Nitrogen-Vacancy [N-V] colour centre in diamond has been recognised as a remarkable source for emitting single-photon light pulses on demand. This system has been used to implement single-photon quantum key distribution within realistic operating conditions and to observe single-photon interference as examples of wave-particle duality. However, NV centers emits a 100 nm broad spectrum in the red and near infra-red region which makes practical use in daylight very hard. Spectral filtering could be a solution, but at the expense of a severe decreases of single-photon emission rate.The wide variety of colour centres in diamond offers a unique opportunity to optimize single-photon emission properties. Recently, Nickel-related point defects in diamond arose strong interest. These defects can be found in some natural type II-a diamonds and also in high-pressure high-temperature diamonds where Nickel is used as a solvent/catalyst for the crystal growth. Compared to the [N-V] colour centre emission, the photoluminescence of individual Ni-related colour centre has several striking features: a narrow band emission around 800 nm almost entirely concentrated in the zero phonon line, corresponding to a spectral width of the order of 1 nm; a nanosecond excited level lifetime; and a linearly polarized light emission. It was also shown that these colour centres can be fabricated in a controlled way in chemical vapor deposited (CVD) diamond thin films. This breakthrough in diamond defect control opens numerous possibilities for the development of highly efficient diamond-based single-photon sources.In this talk we report on the observation of individual Ni-related colour centres in well isolated CVD grown nanodiamonds. Using a continuous-wave titanium-doped sapphire laser tunable between 690 nm and 770 nm, we have measured the excitation spectrum of these defects in order to optimize the signal-over-background ratio corresponding to the detection of their photoluminescence. At excitation of 765 nm, we got the best photoluminescence performance achieving a signal-over-background ration of 80. Based on this result, a triggered single-photon source was built using pulsed excitation at a wavelength of 765 nm. The pulsed excitation source is a frequency-doubled pulsed laser amplified with a fibre amplifier. The pulse duration is about 5 ps, which is much shorter than the radiative lifetime of the colour centres, an appropriate to emit a single photon per excitation pulse. Under pulsed excitation, antibunching has been observed proving that we excited a single emitter. Our triggered single-photon source delivers 30 kcts/s single-photon pulses at an excitation repetition rate of 20 MHz.
12:15 PM - P12.3
Defects in Diamond for Quantum Information Processing.
Chiranjib Mitra 1 , Anthony Stanley-Clarke 1 , Haitao Ye 1 , Gavin Morley 1 , Christopher Kay 2 , A Marshall Stoneham 1 , Richard Jackman 1
1 London Centre for Nanotechnology, University College London, London United Kingdom, 2 Department of Biology, University College London, London United Kingdom
Show AbstractThere has been much interest recently in the use of diamond for quantum computing and quantum cryptography applications. This is in part due to the long-lived nature of several of the spin states that may be used as qubits. One of the proposed paradigms relies on the use of phosphorus and nitrogen centres, whilst less well defined defect centres may also be useful. To ascertain which defect state systems may be of most use we have initiated a study of radiative lifetime excited states from photoluminscence and spin states observed by electron-spin resonance (esr). When combined this information can be used to determine the presence of suitable levels. In this paper we present results obtained from a large number of single crystal diamonds of different colours, and discuss the defects that may be of most interest to QIP.
12:30 PM - **P12.4
Diamond Based Quantum Information Processing.
Steven Prawer 1
1 Center for Excellence for Quantum Computer Technology and Quantum Communications Victoria, University of Melbourne, Parkville, Victoria, Australia
Show AbstractOptically emitting defect centres in diamond display a range of unique quantum properties that offer exciting possibilities for the construction of quantum devices which employ optical single-spin read-out. In this talk I will review these remarkable properties and explain why diamond is an ideal material for use in the fabrication of (i) single photon sources for quantum communications, (ii) optical fibre-based single spin read out systems, (iii) photonic platforms for the investigation of quantum entanglement in solid state systems and (iv) optical regenerators and non-linear quantum gates. The toolkit of available fabrication strategies which are used to engineer devices taking advantage of these unique properties will be presented. Our most recent results include demonstrations of (i) optical fibre based single photon sources based on Nickel and Nitrogen optical centres, (ii) waveguiding of light in structures hewn from single crystal diamond, (iii) Electrical Stark shift of the frequency of single optical emitters, (iv) coupling between the spins between single NV and N atoms in devices engineered by ion implantation, and (v) electromagnetically induced transparency in single NV centres. These crucial demonstrations establish the feasibility of a defect tolerant architecture for the fabrication of a few (~10-50 ) qubit diamond based quantum information processor.
P13: Applications
Session Chairs
Thursday PM, November 29, 2007
Independence W (Sheraton)
2:45 PM - P13.1
UNCD-based Diamond-on-insulator (DOI) Starter Wafers for MEMS.
Nicolaie Moldovan 1 , Nikhil Neelakantan 1 , Charles West 1 , Neil Kane 1 , John Carlisle 1
1 , Advanced Diamond Technologies, Inc., Romeoville, Illinois, United States
Show AbstractIn this talk we present our work over the past year to develop and bring to market a series of foundry-quality MEMS DOI (Diamond-on-Insulator) “starter” wafers based on thin films of ultrananocrystalline diamond (UNCD) integrated with other typical MEMS materials (oxides, metals, etc.), with the overarching goal of getting UNCD into the hands of MEMS designers in industry and academia. UNCD has proven its advantages for MEMS components through its exceptional hardness, Young’s modulus, toughness, acoustic velocity, smoothness, uniformity, bio-compatibility, and tunable electrical and thermal conductivity. The commercialization of diamond MEMS products however is inhibited by limited (high) quality diamond production capabilities, little experience with diamond by end users, and concerns that the seeding process (precursor of diamond growth) may lead to contamination issues. Advanced Diamond Technologies, Inc. (ADT) has solved the problem of thickness uniformity, sp3/sp2 ratio uniformity, grain size uniformity, adhesion, and roughness (<10 nm rms as deposited), but problems remain with the stress level (400 to 700 MPa, compressive), particle density (>102/ cm^2 particles >1 micron in size, mainly due to non-clean room processing), and limited uniformity of the acoustic velocity (14-16 km/s). Bringing all of these properties to within 2% from wafer to wafer and over the surface of a given wafer is a requirement for most MEMS applications in addition to devices exhibiting clear performance and/or cost advantages over incumbent technologies. The present DOI product targets users at various levels (small companies, foundries, research centers) who want to enter the diamond MEMS realm. Diamond MEMS has great potential in RF-MEMS (resonators, filters, oscillators for wireless communication and information technology), bio-implantable chips (artificial retina, cochlear implants, implantable ID chips), electronics and material research (AFM probes, data storage devices, x-ray and electron optics), sensors (SAW sensors, vibrating cantilever sensors, etc). Ultimately the goal is to develop a full UNCD MEMS module capable of insertion into foundries in both industrial and academic settings.
3:00 PM - P13.2
Nanocrystalline Diamond as a Dielectric for SOD Applications.
Mose Bevilacqua 1 , Abioye Odunsi 1 , Aysha Chaudhary 1 , Niall Tumilty 1 , Haitao Ye 1 , James Butler 2 , Richard Jackman 1
1 London Centre for Nanotechnology, University College London, London United Kingdom, 2 , Naval Research Laboratories, Washington, Washington, United States
Show AbstractSilicon-on-insulator (SOI) technology is now well established for the production of high performance VLSI circuits, since. amongst other things, parasitic capacitances are subtantially reduced. However, as device packing densities decrease, there is becoming a major problem removing the heat created locally due to power losses - silicon dioxide which is currently used as the insulating layer being a poor thermal conductor. A possible solution to this problem is the replacement of silicon dioxide with an insulator with a uch higher thermal conductivity - diamond. Whilst large area single crystal diamond films remain a target for the research community, in the near-to-mid term the only diamond technology that is likely to provide flat, homogenious and large area films, is based around the growth of nanocrystaline diamond (NCD).If NCD is to find a role within SOD a number of issues need to be addressed. Those of concern within this paper are the dielecrtric quality of the NCD, given the presence of the numerous grain boundaries, and the electrical nature of the interface formed between the NCD and the silicon. To address these points we have used impedance spectroscopy and C-V methods, and can report exciting results - some forms of NCD can display dielectric characteristcs that are close to those of ideal diamond.
3:15 PM - P13.3
Thermal Conductivity of Nanocomposites Based on Diamonds, Detonation Nanodiamonds and Fullerenes.
Sergey Kidalov 1 , Fedor Shakhov 1 , Alexander Vul' 1 , Maria Yagovkina 1
1 , Ioffe Physico-Technical Institute of the Russian Academy of Science, St.Petersburg Russian Federation
Show AbstractWe studied the sintering mechanisms and thermal conductivity of composites based on well purified detonation nanodiamonds (ND) prepared by Dr. Aleksenskii A.E. The thermal and electrical conductivities of composites from natural diamonds of 10-14 μm in size were also examined. Both types of composites were sintered at high pressures (5.0–7.0 GPa) and high temperatures (1200-2300 °C) for 10-25 seconds. High-pressure chamber was a «toroidal» type with 6 mm inner diameter. The diameter of the sintered samples is about 3-4 mm, and the height is about 4-5 mm. It was found that the thermal conductivity of composites from natural diamonds increased as the sintering temperature approached the diamond-graphite equilibrium in the pressure range of 4.5-6.5 GPa because of the surface graphitization of the diamond samples. Above the phase equilibrium temperature, the thermal conductivity was observed to decrease due to the sample bulk graphitization. The maximum value of this parameter for the ND samples was observed at approximately 1900 °C. Higher temperatures caused sample damage at lowered pressures, which seems to be due to the ND transition to the nondiamond carbon phase possessing a lower density. When we added 5 wt% of C60 fullerene to the initial ND, the diamond transition to a nondiamond carbon-like state occurred at a temperature below 1400 °C and the thermal conductivity increased from 50 to 100 W/(m*K).Thermal conductivity was found to be about 50 W/(m*K) for the ND samples and about 500 W/(m*K) for the microdiamonds.The thermal conductivity measurements were done by the steady state technique in the temperature range 30-200°C in vacuum. The temperature gradient was measured by two thermocouples on sample’s surfaces. The heat flux magnitude was defined by a reference copper sample pasted in series with the samples.Also the density of the samples of different compositions was measured. We have found there is no dependence between the density and the thermal conductivity of the samples prepared from the same starting material.This study was supported by the RFBR grant 06-08-00944-a, and partly, by the State Contract N02.513.11.3213 and N02.523.11.3003 of Ministry of Science and Education of the Russian Federation.
3:30 PM - P13.4
The Diamond Nanobalance.
Oliver Williams 1 2 , Vincent Mortet 1 2 , Ken Haenen 1 2
1 Institute for Materials Research, Hasselt University, Diepenbeek Belgium, 2 Division IMOMEC, IMEC vzw, Diepenbeek Belgium
Show AbstractIn 1959 the foundations of what is now the Quartz Crystal Microbalance (QCM) were laid down in the derivation of the Sauerbrey equation, which related the shift in resonant frequency of an oscillator with applied mass for a bulk acoustic wave oscillator. Thus micro-graviometry was born and in the nearly 50 years since, the QCM has been implemented in practically every laboratory in the world, be it for simple vacuum deposition monitoring, immunosensing, DNA detection or sophisticated macro-molecule visco-elastic characterisation. Following the discovery that QCMs can operate in liquids, further development of the technique lead to simultaneous electrochemistry and visco-elastic measurements. For the QCM, one of the most complicated areas is the surface and it’s stability. For many simple applications such as metal deposition monitoring this is not crucial, but for monitoring antibody-antigen interactions for example, the long-term stability of the surface functionalisation is critical. For most QCM electrodes this is rather poor, such as gold-thiol strategies. Diamond has been shown to exhibit the most stable functionalised surface of all the semiconductors, and this could have be a crucial advantage for pathogen detection, immunosensing, toxin monitoring, stripping voltammetry etc. Diamond also exhibits low friction, extreme chemical stability and bio-inertness, tuneable wettability to the nano scale with simple stable surface terminations and the widest electrochemical window / lowest noise floor for electrochemical electrodes. Thus a conductive diamond coating could be particularly interesting for biological and electrochemical QCM applications. Unfortunately the curie point of quartz is below that of conventional diamond deposition temperatures, rendering the resulting sensor non – piezoelectric. The novel solution we present here is to replace the quartz of the QCM with a high temperature stable piezoelectric such as Langasite or Gallium Orthophosphate. These materials can withstand the high temperatures and have the added advantage of higher piezoelectric coupling coefficients. The resulting device was coated with nanocrystalline diamond and exhibits clear resonant behaviour in air and liquid. We have successfully fabricated devices operating at 2.5, 5 and 9MHz. As the device is no longer based on quartz and is capable of detecting less than ng masses we term the device the “Diamond Nanobalance”.
3:45 PM - P13.5
Thermal, Mechanical and Microwave Characteristics of Nanocrystalline Diamond Bridges.
Srinath Balachandran 1 , Joachim Kusterer 2 , Dane Thompson 3 , Thomas Weller 1 , Ashok Kumar 4 , Erhard Kohn 2
1 Electrical Engineering, University of South Florida, Tampa, Florida, United States, 2 Electron Devices and Circuits, University of Ulm, Ulm Germany, 3 , Ansoft Corporation, Pittsburg, Pennsylvania, United States, 4 Mechanical Engineering, University of South Florida, Tampa, Florida, United States
Show AbstractNanocrystalline diamond due its outstanding thermal, mechanical and tribological properties is an ideal candidate for MEMS/NEMS devices. Nanocrystalline diamond based MEMS devices increases the reliability and life time of the switch and it mitigates the problems of stiction, charge trapping, surface wear and cold welding found in traditional all metal RF-MEMS switches. In this work, nanocrystalline diamond cantilever beams and bridges have been fabricated on a low resistive silicon substrate by using standard micromachining techniques (Figure 1). The diamond structures are then integrated onto an alumina substrate wherein microwave transmission lines in the microstrip and coplanar waveguide (CPW) topology have been fabricated. The diamond bridges are integrated using a combined soldering and flip chip technique. The micromachined bridges are thermally actuated using a bi-metal actuation scheme. In this thermal actuation scheme, the difference in coefficient of thermal expansion between copper and diamond bends the diamond bridge and switches the bridges to the actuated state. In the CPW topology, RF-MEMS switches and tunable planar inductors are realized using the micromachined devices. These devices are fabricated on a 650 micron thick alumina substrate and its microwave characteristics are analyzed in the frequency range of 5-30 GHz. The switches yield a return loss of 15 dB and an insertion loss of 0.2 dB at 20GHz. An inductance ratio of 2.2 is achieved by the tunable inductors at 30 GHz. Transient thermal fluctuations and structural changes in the diamond actuator can be determined in simulation. To accomplish this, the volumetric and surface loss densities are extracted from the low and high frequency electromagnetic field simulations. The combined field loss density from Maxwell/HFSS is then applied as a source for the thermal and structural simulations in ePhysics. With this methodology, the interactions between electromagnetic field sources and induced heating/deformation in the diamond actuator can be analyzed on a computer.
4:00 PM - P13:Applications
BREAK
P14: Surfaces
Session Chairs
Thursday PM, November 29, 2007
Independence W (Sheraton)
4:30 PM - **P14.1
The Oxidation Mechanism of Diamond.
Phillip John 1 , Michael Anderson 1 , Maria Stoickou 1
1 School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh United Kingdom
Show AbstractThe oxidation of diamond at high temperatures has been studied since the elemental composition was established by Lavoisier. Despite the ensuing work, there remains considerable uncertainty over the detailed mechanism of the thermal oxidation of diamond. Naturally occurring and synthetic single crystal diamond stones contain significant defect densities and the incorporation of impurities such as nitrogen and transition metals. Atomically smooth (100) surfaces of such samples are exceedingly difficult to prepare given the cleavage energy of the (100) plane is higher than the other low index planes. Furthermore, mechanical polishing of diamond is known to result in micro-grooves and off-axis alignment of the plane.Data obtained from high quality homoepitaxial or oriented heteroepitaxial layers are likely to be free from problems associated with growth or polishing defects. This paper will present a comparison of the thermal oxidation kinetics of the low index planes of CVD diamond in dry oxygen with kinetic simulations based on QM potential energy profiles.
5:00 PM - P14.2
Electrochemical Charge Transfer to Diamond, Carbon Nanotubes and Gallium Nitride.
Vidhya Chakrapani 1 , John Angus 1 , Alfred Anderson 1 , Kathleen Kash 1 , Gamini Sumanasekera 2
1 , Case Western Reserve University, Cleveland, Ohio, United States, 2 , University of Louisville, Louisville, Kentucky, United States
Show AbstractHydrogen-terminated diamond actively interacts with humid air giving rise to a p-type surface conductivity [1, 2]. The direction of electron transfer between diamond and its surroundings depends on the relative positions of the Fermi level of diamond and the chemical potential of electrons in the surrounding medium [3]. In humid air the electron chemical potential is determined by the oxygen redox couple in an adsorbed water film [4],O2 + 4H+ + 4e− = 2H2O,and consequently is a function of pH, oxygen partial pressure and relative humidity. The effect is not confined to diamond, but is observed in other semiconductors, e.g., carbon nanotubes and GaN, when the band lineup is appropriate. The conductance of single-walled, semiconducting nanotubes increases and the sign of the Seebeck coefficient changes from negative to positive upon exposure to humid air. In GaN the charge transfer is to midgap states and directly mediates the intensity of the yellow band and near-band-edge emission. Since adsorbed water films on solids are ubiquitous in humid air [5], electrochemically mediated charge transfer can occur in many situations and may explain disparate results encountered with semiconductors and other solids that have been exposed to air. [1] M. I. Landstrass, and K. V. Ravi, Appl. Phys. Lett., 55, 975 (1989).[2] R. S. Gi et al., Jap. J. Appl. Phys. Part 1 38, 3492-3496 (1999).[3] F. Maier, M. Riedel, B. Mantel, J. Ristein, L. Ley, Phys. Rev. Lett. 85 (2000) 3472-3475.[4] V. Chakrapani, S. C. Eaton, A. B. Anderson, M. Tabib-Azar, and J. C. Angus, Electrochem. and Solid State Lett. 8 (2005) E4-E8.[5] A.W. Adamson, “Physical Chemistry of Surfaces,” John Wiley, NY, 4th edition, 1982.
5:15 PM - P14.3
STM Characterization of Low Dimensional Surface Electronic Properties of Undoped Diamond in Buffer Solutions.
Nianjun Yang 1 , Hiroshi Uetsuka 1 , Hideyuki Watanabe 1 , Takatoshi Yamada 1 , Christoph Nebel 1
1 Diamond Research Center, National Institute of Advanced Industrial Science and Technology, Tsukuba Japan
Show AbstractTheoretical calculations by the Schrödinger and Poisson equations show that the electronic density-of-state (DOS) distribution at the surface of hydrogen terminated diamond has a two-dimensional (2D) system. However, no experimental evidence for a true 2D property has been presented up-to-now. This has been attributed to macroscopic electronic disorder, arising by surface roughness, imperfect H-termination, surface defects and ionic scattering. We report here for the first time about scanning tunneling microscopy experiments (STM) applied in air and buffer solutions on atomically flat, homo-epitaxially grown, undoped CVD diamond to characterize local electronic properties of the DOS with nanometer resolution. Tunneling currents (I) were measured as a function of applied potentials (V). The DOS is calculated by derivation (dI/dV) of the currents. For positive potentials to the diamond with respect to the Pt0.8Ir0.2 STM tips, well defined tunneling current modulations are detected, which arise from a 2D electronic levels. For negative potentials, only a continuous DOS can be detected. This is in general agreement with our previously presented calculations about surface electronic properties of undoped diamond, where a 2D system, composted out of heavy-, light- and split-off hole-states are introduced. The data will be discussed in detail and compared to results available in the literature.
5:30 PM - P14.4
Surface Transfer Doping to Adsorbates Covalently Bonded on Diamond.
Yu Lin Zhong 1 , Kian Ping Loh 1
1 Chemistry, National University of Singapore, Singapore Singapore
Show AbstractSurface transfer doping of diamond to acid mist layer was first discovered and subsequently extended to electron-withdrawing adsorbates such as fullerene and tetrafluoro-tetracyanoquinodimethane. Such novel mechanism allows the fabrication of nano-scale planar doped electronic devices with tuneable doping level controlled by the surface adsorbates. However, to-date, surface transfer doping was demonstrated only on H-terminated diamond which unfortunately is prone to oxidation overtime. In this work, we seek to covalently link surface dopants onto diamond in order to create a highly stable channel.C60 and fluorinated-C60 were covalently linked onto diamond via UV photochemical functionalization of H-terminated diamond in the fullerene solution (1 mg/ml in toluene). The functionalized diamond substrates were rinsed in boiling toluene and subjected to ultrasonication to remove any physisorbed fullerene. The presence of C60 and energy level was determined by UPS while surface transfer doping was observed through XPS core-level C 1s shift. Furthermore, covalently bonded monolayer coverage was confirmed through AFM “scratching” experiments. To extend the variety of molecules covalently linked onto diamond, we first functionalized the diamond surface via spontaneous reduction of 4-bromophenyldiazonium tetrafluoroborate. Subsequently, target functional boronic acids can be linked via surface Suzuki coupling which provides uninterrupted conjugation between the target molecules and diamond. The target molecules can range from molecular cage host to redox species such that they may behave as tuneable dopants. For all grafted samples, gold contacts were e-beam deposited and their surface I-V characteristics were recorded for comparison.
5:45 PM - P14.5
Adsorption Studies of Fullerene and Fluorinated Fullerene at Diamond Surfaces.
John Foord 1 , Hao Wang 1
1 Department of Chemistry, University of Oxford, Oxford United Kingdom
Show AbstractThe adsorption of fullerene and fluorinated fullerenes at diamond surfaces is of interest in view of reports that these adsorbates can induce surface conductivity as a result of electron transfer from the diamond valence band to the deep acceptor levels which these molecules possess. Nevertheless, there have been view dedicated adsorption studies of these chemical systems. In the present work we therefore use photoelectron, electron energy loss and desorption techniques to examine the interactions which occur when adsorption takes place.Studies are carried out on both hydrogen-free and hydrogen-terminated surfaces, and we compare the behaviour observed on diamond with that seen on other Gp IV semiconductors. The XPS spectra of adsorbed fullerenes look very different depending on whether adsorption occurs on the H-terminated or H-free surface. The differences are interpreted in terms of the unusual influence which the different electron affinity can exert on the spectral appearance. Monolayer and multilayer adsorption occurs depending on surface coverage, and the different desorption kinetics and phase stabilities are determined for the various adsorbate coverages, types of surface termination and types of fullerene. Thes results are found to be very different to the well-characterised corresponding Si adsorption systems.
P15: Poster Session
Session Chairs
John Foord
Oliver A. Williams
Friday AM, November 30, 2007
Exhibition Hall D (Hynes)
9:00 PM - P15.1
Arsenic and Antimony Doping: An Attempt to Deposit n-type CVD Diamond.
Paul May 1 , Martin Davey 1
1 School of Chemistry, University of Bristol, Bristol United Kingdom
Show AbstractFinding a suitable n-type dopant is a key requirement if CVD diamond is to play a major role in future electronic devices. However, previous attempts to make n-type diamond by doping with elements such as N, S or P have either been unsuccessful, or have produced films with electrical characteristics that are not adequate for many proposed devices. Theoretical studies have recently shown that arsenic and antimony may act as n-type dopants. However, the large size of these atoms has led to the suggestions that incorporation efficiency into the diamond lattice may be low. This, coupled with the high toxicity of As and Sb compounds has resulted in no experiments being reported in the literature on their use as dopants for CVD diamond, despite these elements being quite commonly used in the Si industry.In this paper we shall report the results of experiments to try to deposit n-type CVD diamond using (i) AsH3 as a gas phase source of arsenic, and (ii) evaporated Sb or Sb(Ph)3 as a source of antimony. Electrical conductivity measurements will be presented to show if doping is achieved. The films will be characterised by laser Raman, SEM and TEM, to see changes in microstructure, and by SIMS to relate the gas phase concentration of As/Sb with the concentration incorporated in the films.
9:00 PM - P15.10
Theoretical Analysis of the Graphitization of a Nanodiamond.
S. Joon Kwon 1 , Jae-Gwan Park 1
1 Materials Science and Technology Division, Korea Institute of Science and Technology, Seoul Korea (the Republic of)
Show AbstractA theoretical analysis of the graphitization of a nano-size diamond (nanodiamond) in the metastable state is given. During annealing at a relatively lower temperature, a nanodiamond suffers morphological transition into a nanodiamond-graphite core-shell structure. A thermodynamic analysis on the stability of the nanodiamond showed that the phase-diagram (relationship between the annealing temperature and radius) of the nanodiamond-graphite has three regimes: smaller nanodiamond, nanodiamond-graphite, and larger nanodiamond. Particularly, these regimes of nanodiamond-graphite are due to an additional phase boundary by taking into consideration the maximum size of the nanodiamond which can be graphitized. In the theoretical analysis, the most probable and the maximum volume fractions of graphite in the nanodiamond were about 0.76 and 0.84 respectively, independent of the annealing temperature and the initial radius of the nanodiamond graphitized. Therefore, the nanodiamond is not completely transformed into graphite by simple annealing at relatively lower process temperature and pressure. The highest graphitization probability decreased with increasing annealing temperature. For the systematic examination of the graphitization of the nanodiamond, Raman spectra for the F2g-vibration mode of nanodiamond was calculated, and the variation in properties of the spectra line was strongly dependent on the graphitization temperature and the initial size of the nanodiamond.
9:00 PM - P15.11
The Origin of Field-induced Electron Emission from N-doped CVD Diamond Characterized by Combined XPS/UPS/FES System.
Hisato Yamaguchi 1 2 , Yuki Kudo 1 , Tomoaki Masuzawa 1 , Masato Kudo 3 , Takatoshi Yamada 4 , Yuji Takakuwa 5 , Ken Okano 1 2
1 Department of Physics, International Christian University, Mitaka, Tokyo Japan, 2 School of Materials Science, Japan Advanced Institute of Science and Technology, Nomi, Ishikawa Japan, 3 Diamond Research Center, AIST, Umezono, Tsukuba Japan, 4 Technical Division 1, JEOL, Akishima, Tokyo Japan, 5 IMRAM, Tohoku University, Aoba, Sendai Japan
Show AbstractElectric field of less than 5 V/um is enough to extract electrons from CVD diamond, whereas field of one to two orders of magnitude higher is needed to extract electrons from metal emitter tips. Diamond has various advantages as an electron emitter in addition to the low-threshold voltage, negative electron affinity (NEA), high thermal conductivity, and high chemical stability. The difficulty in clarification of electron emission mechanism is the factor preventing diamond from being used in practical applications. Quite a few numbers of possible mechanisms have been proposed based on conventional emission current-anode voltage (I-V) characteristics, however, difficulty remained in the determination of origin for emitting electrons. In our previous study, we have succeeded in determining the origin for lightly nitrogen (N)-doped CVD diamond by using combined x-ray photoemission spectroscopy / ultraviolet photoemission spectroscopy / field emission spectroscopy (XPS/UPS/FES) system. The origin at 1.47 eV above valence band maximum (VBM) was consistent with donor level for aggregated N. The origin was at VBM for natural IIb diamond measured as a reference, indicating the emitted electrons strongly depend on the dopant incorporated in the diamond. In this study, the origin of emitting electrons for heavily N-doped CVD diamond was characterized by the means of combined XPS/UPS/FES. Extremely low-threshold electron emission at 0.5 V/um is still one of the lowest threshold voltages. Such a low-threshold emission may be possible if electrons are somehow injected to conduction band of diamond and emitted into vacuum through NEA surface. Hence, we strongly believe the determination of the origin for heavily N-doped CVD diamond leads to the clarification of mechanism for low-threshold electron emission from diamond. The system in which we have developed for this study consists of ultraviolet source built in an X-ray photoelectron spectrometer. The diamond sample could be negatively biased up to 4kV relative to the mesh grid for FES. Individual spectroscopy of XPS was performed prior to the combined spectroscopy to determine any possible contaminants on CVD diamond. Peaks referred to C1s and O1s of diamond were observed in addition to Gold, used in a mesh grid set above the sample. Combined spectroscopy of UPS/FES was then, conducted on the CVD diamond to identify the origin of field emitted electrons. The diamond was first illuminated by He I excitation for photoemission. NEA with the typical spectra shape for diamond was observed. After confirming stable operation of individual UPS, negative voltage was applied simultaneously for field emission. Exceeding threshold voltage, a sharp peak, which can be referred to field-emitted electrons appeared in addition to typical UPS spectra. The origin of emitting electrons as well as its dependence on the applied voltage will be discussed.
9:00 PM - P15.12
Barrier Height Difference Induced by Surface Terminations for Field Emission from P-doped Diamond.
Yuki Kudo 1 , Masuzawa Tomoaki 1 , Hisato Yamaguchi 1 , Shin-ichi Shikata 2 , Christoph Nebel 2 , Takatoshi Yamada 2 , Ken Okano 1
1 Physics, International Christian University, Mitaka, Tokyo Japan, 2 Diamond Research Center, National Institute for Advance Industrial Science and Technology (AIST), Tsukuba Japan
Show AbstractCold cathodes are essential elements for vacuum nano-electronics in order to realize devices such as field emission displays. An ideal cold cathode would operate under low vacuum and with a small-applied voltage, where diamond could be one of the most appropriate candidates. This is mainly because the electron affinity is observed to exhibits very low, or even negative, and the chemical stability is extremely high. In addition, n-type diamond could be developed by phosphorus (P)-doping from the recent invention [1]. Although the resistivity of P-doped diamond is not as low as the B-doped, the confirmed n-type electron conduction might result in the low threshold electron emission. Surface termination is also a key technology for using diamond as a practical cold cathode because the H-terminated surface is reported to have negative electron affinity, while the O-terminated indicates the small positive affinity. The difference can be explained by the existence of an internal depletion layer preventing electrons from approaching to the surface [2]. However, field emission mechanism associated with surface termination has not been clarified so far.In this paper, the field emission properties of "reconstructed" and "oxidized" P-doped diamond have been compared in order to clarify the electron emission mechanism of P-doped diamond. The preparation procedures of the reconstructed and oxidized surfaces were as follows; H-terminated diamond was annealed in a high vacuum system (< 1 x 10-7Pa) at 900°C for 10min.The surface was characterized by reflective high energy electron diffraction RHEED experiments, indicating C:(111)-(2x1) reconstruction. This was in agreement with data from the literature, where it has been demonstrated that annealing over 727°C gives rise to a diamond surface reconstruction from C: (111)-(1x1) to C: (111)-(2x1). The oxidized surface was achieved by boiling the diamond in a mixture acid of H2SO4 and HNO3 (=3:1) at 200°C for 60 min. As a result, the electric field of vacuum were evaluated to be 5.0 V/um for reconstructed surface and 25 V/um for oxidized surface by measuring the emission current versus anode voltage characteristics under variety of anode-cathode spacings. It was confirmed that the reconstructed surface required only 1/5 of the electric field required for the oxidized surface to obtain emission current of 1nA. This ratio of the electric field enables us to evaluate the ratio of the barrier height as 1/3.Although the emission mechanism of P-doped diamond has not yet been clarified only from the present results, we have confirmed that the surface termination indeed affects the emission threshold which might lead to the complete mechanism in the near future.[1] S. Koizumi, K. Watanabe, M. Hasegawa, H. Kanda. Science. 292 1899 (2001).[2] T. Yamada et al, J. Vac. Sci. Tech. B 24(2), 967 (2006).
9:00 PM - P15.13
High Thermoelectric Effect in Nanocarbon Generated by the Ballistic Phonon Drag of Electrons.
Alexander Vul 1 , Evgeny Eydelman 1 2
1 Solid State Electronics, Ioffe Physico-Technical Institute, St.Petersburg Russian Federation, 2 , St. Petersburg Chemical-Pharmaceutical Academy, St.Petersburg Russian Federation
Show AbstractThe thermoelectric power and thermoelectric figure of merit in carbon nanostructure consists of graphite-like (sp2) and diamond-like (sp3) regions have been investigated. Probability of electron collisions with quasi-ballistic phonons in sp2 regions has been analyzed for the first time. We have shown that the probability is not small. We have analyzed the influence of various factors on the process of electron-ballistic phonon drag effect (phonon drag effect). The thermoelectric power and thermoelectric figure of merit under conditions of ballistic transport were found to be substantially higher than those in the case of the drag by thermalized phonons or of electron diffusion. The thermoelectric figure of merit (ZT) in the case of a ballistic phonon contribution to the phonon drag of electrons should be in 50 times higher for chaotic phonons and 500 higher than that in the case of diffusion process. In that case the ZT should be record (ZT = 2-3).
9:00 PM - P15.14
Field Electron Emission from Carbon Nanostructures: Theoretical Models and Reality.
Artur Dideykin 1 , Evgeny Eydelman 1 2 , Alexey Babenko 2 , Konstantin Reikh 1
1 Solid State Electronics, Ioffe Physico-Technical Institute, St Petersburg Russian Federation, 2 , St. Petersburg Chemical-Pharmaceutical Academy, St.Petersburg Russian Federation
Show AbstractThe unique field electron emission (FEE) properties of carbon nanostructures were discovered more than 10 years ago. Since that time different nanocarbon materials (NCM), such as nanotubes, nanodiamonds, diamond-like films still remains promising for the new generation of vacuum electronic devices. However, in spite of intensive investigations there is no significant progress in this field.Here we have reviewed current theoretical models for field electron emission included [1,2,3,4] and compared them with published experimental data as well as the results of our own experiments on the NCM. The main conclusion of the most investigations on field emission from NCM is that one cannot explain the observed levels of emission current by simple Fowler-Nordhaim model. To fit the experimental values of current one needs to use the unrealistic values of work function (0.1 – 0.01 eV) and has to assume the local concentration of electric field with aspect ratio more than 1000. However, the direct calculation gives the noticeable drop down of work function for instance, for the edges of the separate graphene sheets, only at the applied field 1011-1012 V/cm. The published results and our investigations have shown that the emission current concentrates in a number of emission centers while the rest surface of the NCM emitter remains passive and keeps the work function in agreement with calculations. The important feature of the FEE from the NCM was that to obtain the observed values of the emission current and threshold electric field one had to perform so-called activation of the emission by short time applying extra value of field to the sample. Such action caused the break down-like appearance and increasing of the emission current. After activation the current – field dependences of the material still remain stable and reproducible during several hours and then the vanishing of emission had taken place. The repeated activation returned the same value of emission current. Such a behavior of the emission is quite similar to the effect of anomalous secondary emission, observed by Malter [4]. We suppose that the models suggested in [1, 2], have to be modified for adequate description of that field electron emission from the NCM. 1.A.T.Dideikin, E.D.Eidelman, A.Ya.Vul’. Solid State Communication, 126, 495 (2003).2.N. Obraztsov et al. Journal of Experimental and Theoretical Physics, October 2001, v. 93, Issue 4, pp. 846-852.3.V.D.Frolov, V.I.Konov et al. Diam&Rel. Mat. 10 (2001) 1719-1726.4.V.Malter. Phys.Rev. 49. 378. 1936; 50, 48, 1936.
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Diamond Film Synthesis on Glassy Substrates for Heat-spreading Applications.
Katsunori Yagi 1 , Naoyuki Yonekyu 1 , Yoshiki Takagi 1
1 Takagi Laboratory, Teikyo University of Science & Technology, Uenohara-city, Yamanashi-pref, Japan
Show AbstractDiamond has the highest thermal conductivities among all materials. On the other hand glassy materials have relatively low thermal conductivities. Therefore, diamond film on glassy substrate can conduct heat from electronic devices to cooling fans or other heat spreaders. Diamond coating on glassy substrates with specially designed patterns and parts of the surfaces, results more effective heat spreader for electronic devices, and in near future, realize higher density and smaller ICs. Diamond film was synthesized on glassy substrates, such as borosilicate and soda lime glasses, successfully with HFCVD (hot-filament chemical vapor deposition) method. And selective deposition on borosilicate glass, successfully with our unique masking technique.Heat SpreaderElectronic devices were set up on transparent substances, for example, glassy materials. Heat comes from electronic devices was accumulated on low thermal conductive substrate. Though, heat comes from electronic devices spread through diamond film with higher thermal conductivity, according to depositing diamond film. In this work, diamond films were synthesized on glassy substrates.Selective DepositionDiamond films were selective deposited on borosilicate glass with special pretreatment, will report at meeting.Non-Alkaline GlassWe have to avoid the possibility of contamination of alkaline element from substrate materials, in industrial field. Therefore, borosilicate glass is the typical choice. Non-alkaline glasses are used for substrates of display equipments.Soda Lime GlassWe also tried the diamond thin film synthesis on soda lime glass. The diamond thin film synthesis to the soda lime glass is a very useful technology to improve various properties of these glass products. Soda lime glass is utilized on many industrial applications.Future ApplicationsDiamond coating on these substances will improve mechanical and chemical stability, and also will improve optical performance of optical lens, comes from high refractive index of diamond, which is utilized on many industrial applications.
9:00 PM - P15.16
The Homogeniety of Carrier Transport Within Epitaxial Boron Doped Diamond Layers.
Haitao Ye 1 , Niall Tumilty 1 , Milos Nesladek 2 , Philippe Bergonzo 2 , Richard Jackman 1
1 London Centre for Nanotechnology, University College London, London United Kingdom, 2 , CEA-LIST, Saclay, Paris France
Show AbstractAs the complexity of device structures that can be fabricated increase, so does our need to understand variations in the nature of carrier transport within the different doped layers used, not just the differences that occur between the layers. Hall effect measurements are commonly used throughout the semiconductor industry t measure free carrier concentrations and mobility values at different temperatures, and we have used this technique extensively with diamond. However, the Hall measurement averages carrier transport information both laterallu across the sample being measured. Moreover, no information on the effect of variations vertically though the layer is achieved. To overcopme this problem, we have used successive etching (RIE)-Hall measurement cycles, as different layers of boron doped diamond are thinned. The results are then compared with 'as-grown' layers of different thicknesses. In this way we have been able to isolate the 'skin-effect' of the layers from inherent inhomogiety of carrier transport within the layers. The results are interesting, showing that there is a clear limit to the useful thinness of a boron-doped diamond epitaxial layer to be used within a device due to surface/interface roughness effects.
9:00 PM - P15.17
The Influence of Surface Roughness on Carrier Transport within Doped Epitaxial Diamond Films I: An Impedance Spectroscopic Study.
Haitao Ye 1 , Niall Tumilty 1 , Mose Bevilacqua 1 , Richard Jackman 1
1 London Centre for Nanotechnology, University College London, London United Kingdom
Show Abstract9:00 PM - P15.18
New Mechanism of Spark Method for Diamond Deposition.
Naoyuki Yonekyu 1 , Yoshiki Takagi 1 , Takayuki Hirai 2 , Hitoshi Kinoh 3 , Osamu Shimizu 3 , Yoshihisa Suda 3
1 , Takagi Laboratory, Teikyo University of Science & Technology, Uenohara-city, Yamanashi-pref Japan, 2 , University of Yamanashi, Yamanashi, Kofu-city, Yamanashi-perf Japan, 3 , MITSUBISHI PENCIL CO., LTD., Fujioka-city,Tokyo-pref Japan
Show Abstract Diamond has recently emerged as important and promising materials for a wide field of optoelectonic and electronic applications. In a current report, the particles were synthesized with spark method in inert gas atmosphere, on various kinds of substrates. We used two graphite rods, one with straight cut shaped and other with sharpened just like screwdriver top, and rods set on the center of the camber, substrate was set up to orthogonalize to the rods. Inert gas was installed up to 100 Torr in the chamber. Various kinds of substrates were set 2-3 mm beneath the rods. Applied electric current kept 40-45A of hreating. With graphite spark method in inert gas atmosphere, synthesized particles were observed with SEM and confirmed as diamond with Raman spectrometer. We successfully synthesized diamond particles with 0.2-1μm in diameter 30-50 seconds without hydrogen gas on various kinds of substrates. As a next stage we have to synthesize the diamond film by present method. Experimental result will be reported on this presentation.
9:00 PM - P15.19
Investigation of Biological Properties for DLC Film Coating on an Artificial Heart Blood Pump.
Kazuya Kanasugi 1 , Yasuharu Ohgoe 1 , Tatsuya Fukui 1 , Kenji Hirakuri 1 , Akio Funakubo 1 , Yasuhiro Fukui 1
1 , Tokyo Denki University, Saitama Japan
Show AbstractDiamond-like carbon (DLC) films have been considerably interesting in a variety of applications, due to their attractive electrical, mechanical, chemical, and biological properties. In our previous work, we have developed a special 3-dimensional type electrode using a large number of small metallic balls, which is possible to adjust to be a shape of the artificial heart blood pump flexibly. We succeeded in the DLC films deposition on an irregular structure such as an artificial heart blood pump by radio frequency (r.f.) plasma chemical vapor deposition (CVD) technique using the special electrode. However, the previous investigations of the DLC film coatings have focused mainly on the deposition technique, without detailed understanding of the coating for biomaterials. In this study, we focus on structural and compositional effects of the DLC films on cellular response. In this experiment, DLC film was deposited on an artificial heart blood pump’s surface uniformly using the electrode. In order to investigate the structural and compositional effects of the DLC film on cellular response, under the film depositions, the DLC film was deposited on the three kinds of polymeric (Polycarbonate: Pc, Polystyrene: Ps, and Polytetrafluoroethylene: PTFE) tips (10 mm ×10 mm) that were put on at the different positions of the blood pump’s surface, respectively. The deposited DLC films were denoted as an DLC/Pc, DLC/Ps, and DLC/PTFE, respectively. And then, the DLC/Pc, DLC/Ps, and DLC/PTFE films were analyzed for the surface properties (structure, chemical composition, roughness and potential) using infrared spectrometer (IR), Ar-laser Raman spectrophotometer (Raman), X-ray photoelectron spectrometer with Mg Kα radiation (XPS), and Atomic Force Microscopy (AFM). Additionally, we measured contact angle of the film’s surface, and mouse fibroblasts have been grown on the DLC film coated for periods of up to 96 hours. The surface results of all the DLC films indicated the non-toxic nature of the surface on the cells, however, we found that the cells spread depended on the surface conditions of the DLC/Pc, DLC/Ps, and DLC/PTFE films, respectively. The surface constitutions were controlled by the deposition conditions of the DLC films. This suggests that the deposition conditions are possible to control an important factor for influencing the biological response of the DLC films surface. This study indicates a good degree of biomedical applications of DLC films which were deposited on a biomaterial’s surface modifications.
9:00 PM - P15.2
785 nm Raman Spectroscopy of CVD Diamond Films.
Paul May 1 , James Smith 1 , Keith Rosser 1
1 School of Chemistry, University of Bristol, Bristol United Kingdom
Show AbstractRaman spectroscopy is a powerful technique often used to study CVD diamond films. Excitation using laser wavelengths in the UV and visible regions are most commonly used, and these typically produce spectra with a limited number of characteristic peaks, including the diamond peak (~1332 cm-1), the D and G bands from graphitic impurities, and sometimes the 1150 and 1450 cm-1 bands from sp2 carbon impurities at the grain boundaries of nanophase diamond. Very little work has been reported, however, for the study of CVD diamond films using near infrared (785 nm) excitation, which is exceptionally sensitive to sp2 carbon. Here we report that when using 785 nm excitation, the Raman spectra from diamond films exhibit a multitude of peaks (over 50) ranging from 400-3000 cm-1. These features are too sharp to be photoluminescence, and are a function of film thickness. For films >30 μm thick and for freestanding films, the Raman peaks disappear, suggesting that we are probing the disordered small-grained interface between the diamond and substrate. Some of the peaks change in relative intensity with time (‘blinking’), and the spectra are very sensitive to position on the substrate – this behaviour is reminiscent of the peak behaviour seen in SERS.
9:00 PM - P15.20
The Influence of Surface Roughness on Carrier Transport within Doped Epitaxial Diamond Films II: A Hall Effect Study.
Niall Tumilty 1 , Haitao Ye 1 , Mose Bevilacqua 1 , Richard Jackman 1
1 London Centre for Nanotechnology, University College London, London United Kingdom
Show Abstract9:00 PM - P15.22
Atomic Clustering in a Highly Hydrogenated Diamond-like Carbon Determined Using Fluctuation Electron Microscopy and Raman Spectroscopy.
Amelia Liu 1 , Raul Arenal 1 2 , Xidong Chen 1 3
1 Materials Science Division, Argonne National Laboratory, Argonne, Illinois, United States, 2 LEM, CNRS-ONERA, Chatillon France, 3 , Cedarville University, Cedarville, Ohio, United States
Show AbstractAmorphous carbons, or diamond-like carbons (DLC) are a compelling choice for protective coatings due to their exemplary hardness, chemical inertness, transparency, low coefficient of friction and wear-resistance.[1] The range of bonding hybridizations of carbon and the ability to add hydrogen to the network allow DLCs to have their properties tuned to make them more graphitic, diamond-like or polymeric.[2] The ratio of carbon bonding (sp2:sp3) and the amount of hydrogen incorporated into the film do not determine film properties uniquely.[3] Clustering of the bonded carbon is another degree of freedom of the structure that must be taken into account; as an example clustering of the sp2 phase dominates the optical and electronic properties.[4]Traditionally Raman spectroscopy has been used to probe clustering in DLC films.[4] Raman spectroscopy accesses this information via the vibrational density of states giving rise to a resonantly enhanced sensitivity to sp2 bonded carbon. In contrast, fluctuation electron microscopy (FEM) is a technique based upon electron scattering; it has equal sensitivity to correlated structures, or medium-range atomic order (MRO) composed of either sp2 or sp3 bonded carbon.[5]Here we present bulk FEM and Raman measurements on a set of highly hydrogenated DLC films that possess strikingly low coefficients of friction.[6] The films were grown using plasma enhanced chemical vapor deposition. A higher proportion of hydrogen in the source gas was found to correlate with the lowest coefficient of friction.[6] Using FEM and Raman we see that increasing hydrogen in the source gas increases the size of the sp2 bonded clusters in the bulk of the film.[7] Such clusters consist of single graphene sheets composed of up to 4 aromatic rings or highly distorted fragments of graphite with multiple associated sheets.[7,8] Additionally, FEM detects a population of sp3 bonded structurally correlated clusters. Simulation of the FEM suggests that these clusters are composed of fragments of the diamond structure consisting of several 6-membered rings in the typical chair conformation.[8] However, to provide the best match to the data this structure must be subject to some particular distortion. [1] J. Robertson. Mat. Sci. Eng. R. 37, 129, (2002).[2] C. Casiraghi, J. Robertson and A. C. Ferrari. Mat. Today. 10, 44, (2007).[3] A. C. Y. Liu, R. Arenal, D. J. Miller, Xidong Chen, J. A. Johnson, O. Eryilmaz and A. Erdemir. Phys. Rev. B. 75, 205402, (2007).[4] A. C. Ferrari and J. Robertson. Phys. Rev. B. 61, 14095, (2000)[5] M. M. J. Treacy, J. M. Gibson, L. Fan, D. J. Paterson and I. McNulty. Rep. Prog. Phys., 68, 2899, (2005)[6] A. Erdemir, O. L. Eryilmaz and G. Fenske. J. Vac. Sci and Technol. 18, 1987, (2000)[7] R. Arenal and A. C. Y. Liu. manuscript in preparation
9:00 PM - P15.23
Elasticity and Mechanical Properties of Nnostructured Carbon.
Maria Fyta 2 1 , Ioannis Remediakis 2 3 , Pantelis Kelires 2 4
2 Physics, University of Crete, Heraklion Greece, 1 Physics, Harvard Univeristy, Cambridge, Massachusetts, United States, 3 Materials Science and Technology, University of Crete, Heraklion Greece, 4 Mechanical Engineering and Materials Science and Technology, Cyprus University of Technology, Limassol Cyprus
Show Abstract9:00 PM - P15.24
Electronic Structure and Hyperfine Tensors of the Nitrogen Vacancy Center in Diamond: ab initio Calculations.
Adam Gali 1 2 , Maria Fyta 2 , Efthimios Kaxiras 2
1 Atomic Physics, Budapest University of Technology and Economics, Budapest Hungary, 2 Physics and School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, United States
Show Abstract9:00 PM - P15.25
THz and Infrared Properties of Superconducting Diamond.
Stefano Lupi 1
1 Department of Physics, University of Rome La Sapienza, Rome Italy
Show Abstract9:00 PM - P15.26
Synthetic Single-Crystal Diamond as Neutron Detector in Fission and Fusion Reactors.
Marco Marinelli 1 , Enrico Milani 1 , Aldo Tucciarone 1 , Gianluca Verona Rinati 1 , Maurizio Angelone 2 , Mario Pillon 2
1 Dip. Ingegneria Meccanica, Università di Roma "Tor Vergata", Roma Italy, 2 , Associazione EURATOM-ENEA sulla Fusione, Frascati Italy
Show AbstractSingle crystal CVD diamond neutron detectors were obtained adopting a multilayer design. A heavily B-doped diamond layer is firstly grown on the HPHT substrate followed by the deposition of the intrinsic diamond sensing layer. The B-doped layer acts as the ground contact, while an Al layer deposited on the intrinsic diamond layer surface is the positively biased contact. A 6LiF layer is finally deposited on the Al contact as a converting material for thermal neutrons, through the 6Li(n,α)T nuclear reaction, while fast neutrons (E > 5.7 MeV) are directly converted inside the sensitive diamond layer though the 12C(n,α)9Be reaction.Many samples, having intrinsic diamond layer thickness ranging from 20 μm to 200 μm have been grown. Preliminary α particle detection test have shown that all the fabricated samples do not need pre-irradiation (priming process) and exhibit a 100% charge collection efficiency with an energy resolution below 1.5%. The performance of these detectors were tested under neutron irradiation from the experimental nuclear fusion reactor Joint European Torus, UK (JET), from the fission reactors TRIGA in Frascati, Italy and from an experimental neutron source FNG in Frascati, Italy.Two diamond detectors are working since March 2006 at JET. The results obtained so far, in terms of stability, reproducibility, efficiency and energy resolution, are extremely encouraging, also in view of their possible use in the forthcoming International Thermonuclear Experimental Reactor (ITER). Another detector was tested in a research fission reactor, placing it 80 cm above the core mid-plane, where the maximum neutron flux is 2.2×109 n/cm2s. Good stability and reproducibility of the device output were found over the whole reactor power range, with no degradation of the detector response. The maximum count rate was 150000 cps at the reactor full power. This count rate was limited by the readout electronics producing multiple pile up processes. After correction for pile up effects, a very good linearity of the diamond flux monitor response was observed vs. a reference fission chamber signal. The effect of both the LiF layer thickness and the intrinsic layer thickness were measured at the Frascati Neutron Generator. The results are compared with theoretical models. The radiation hardness of one of such devices was finally verified by irradiating with 14 MeV neutrons. No evidence on detection properties degradation have been observed after a fluence of 2×1014 n/cm2.
9:00 PM - P15.3
Multi-wavelength Raman Spectroscopy of Nanodiamond Particles.
Paul May 1 , Philip Overton 1 , James Smith 1 , Keith Rosser 1
1 School of Chemistry, University of Bristol, Bristol United Kingdom
Show AbstractRaman spectroscopy is a powerful technique often used to study bulk diamond, CVD diamond films and diamond particles. We have used Raman spectroscopy with 3 different laser excitation wavelengths (near infra red: 785 nm, green 514 nm, and ultraviolet 325 nm) to study diamond particle powder/grit as a function of particles size, ranging from 5 nm to 100’s of μm. These have been compared with the Raman spectra from microcrystalline and nanocrystalline diamond films. We find that the position of the 1332 cm-1 diamond line varies with particle size, but not in a predictable manner. Quantum confinement effects have been discounted as these should only operate at distances <5 nm in diamond. Therefore the origin of the observed peak shifts remains uncertain, but the differences in stress within the particles may be one explanation.
9:00 PM - P15.30
The Influence of Different Surface Terminations on Electrical Transport and Emission Properties for Freestanding Single Crystalline (100) CVD Diamond Samples.
Wim Deferme 1 , Andrey Bogdan 1 , Ken Haenen 1 2 , Ward de Ceuninck 1 2 , Kees Flipse 3 , Milos Nesladek 1 2 4
1 Institute for Material Research, Hasselt University, Diepenbeek Belgium, 2 Division IMOMEC, IMEC vzw, Diepenbeek Belgium, 3 Physics Department, Eindhoven Univ. of Technology, Eindhoven Netherlands, 4 LIST (CEA-Recherche Technologique)/DETECS/SSTM/LTD, CEA/Saclay, Gif-sur-Yvette France
Show Abstract9:00 PM - P15.31
DNA Layers on Nano- and Ultra-nanocrystalline Diamond Characterized by Optical Techniques.
Sylvia Wenmackers 1 , Simona Silaghi 3 , Veronique Vermeeren 2 , Martin vandeVen 2 , Marcel Ameloot 2 , Luc Michiels 2 , Norbert Esser 3 , Ken Haenen 1 , Patrick Wagner 1
1 Institute for Materials Research, Hasselt University, Diepenbeek Belgium, 3 Department Berlin, Institute for Analytical Sciences, Berlin Germany, 2 Biomedical Research Institute, Hasselt University, Diepenbeek Belgium
Show Abstract9:00 PM - P15.32
Study of the Nucleation Mechanism of Nanocrystalline Diamond Films using Ti-based Interlayers.
Michael Daenen 1 , O. Williams 1 2 , A. Hardy 1 , M. Van Bael 1 , L. Zhang 3 , R. Erni 3 , G. Van Tendeloo 3 , K. Haenen 1 2 , M. Nesladek 1 4
1 Institute for Materials Research, Hasselt University, Diepenbeek Belgium, 2 , IMEC, Leuven Belgium, 3 EMAT, University of Antwerp, Antwerp Belgium, 4 , CEA, Paris France
Show Abstract9:00 PM - P15.33
Highly Reactive and Stable BNCD Electrodes: from Electrochemical Activation to Physicochemical Characterisation of the Surface.
Emilie Vanhove 1 , Jacques de Sanoit 1 , Jean-Charles Arnault 2 , Christine Mer 1 , Pascal Mailley 3 , Philippe Bergonzo 1 , Milos Nesladek 2
1 LIST, Laboratoire de technologie des détecteurs, CEA, Gif sur Yvette France, 2 DRECAM, Service Physique et Chimie des Surfaces et des Interfaces, CEA, Gif sur Yvette France, 3 DRFMC, SPrAM , CEA, Grenoble France
Show Abstract9:00 PM - P15.34
Micropowders of Cubic Boron Nitride Ready to Use Phosphors with Emission in UV, Blue and Red Ranges of Spectra.
Elena Shishonok 1 , Sergey Leonchik 1 , John Steeds 2
1 Laboratory of High Pressure Physics, National Academy of Science, Joint Institute of Solid State & Semiconductor Physics, Minsk, ***, Belarus, 2 Physics Department, University of Bristol, Bristol United Kingdom
Show Abstract9:00 PM - P15.35
Thin Diamond Films for Thermal Applications: A New Route to Control the Nucleation Stages.
Samuel Saada 1 , Jean-Charles Arnault 1 , Philippe Bergonzo 1
1 , CEA, Gif sur Yvette France
Show AbstractDiamond has extreme thermal and electrical properties and, thus, it is a perfect candidate for thermal application like Silicon On Diamond technology. However, the properties of thin diamond films are strongly affected by the polycrystalline structure of the films. The first stages of the plasma exposure modified the silicon surface and are of great importance for controlling the nucleation stage in case of Bias Enhanced Nucleation pretreatment. We study the first stages of nucleation correlated to the silicon surface modifications by XPS, AFM and HRSEM. We propose a new approach for improving the film quality by controlling the nucleation step and the choice of the following growth conditions.
9:00 PM - P15.36
Synthesis and Characterization of Smooth/Dense Ultra-nanocrystalline Diamond Films Via Low Pressure Bias-Enhanced Nucleation and Growth.
Ying Chieh Chen 1 2 , Xiao Yan Zhong 2 , Andrew Konicek 3 , David Grierson 4 , Nyan Hwa Tai 1 , I Nan Lin 5 , Bernd Kabius 2 , Jon Hiller 2 , Robert Carpick 6 , Anirudha Sumant 7 , Orlando Auciello 2 7
1 Department of Materials Science and Engineering, National Tsing-Hua University, Hsin-Chu Taiwan, 2 Materials Science Division, Argonne National Laboratory, Argonne, Illinois, United States, 3 Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin, United States, 4 Department of Engineering Physics, University of Wisconsin-Madison, Madison, Wisconsin, United States, 5 Department of Physics, Tamkang University, Tamsui Taiwan, 6 Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, Pennsylvania, United States, 7 Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois, United States
Show AbstractUltrananocrystalline diamond (UNCD) in thin film form is an outstanding candidate material for multifunctional devices, such as MEMS/NEMS, field emission devices, biomedical devices, biosensors, and many others. UNCD films exhibit exceptional mechanical, tribological, electrochemical, and biocompatible properties, similar to those of single crystal diamond. Many groups worldwide are now investigating UNCD film synthesis and properties with an emphasis on multifunctional applications, including electronic and MEMS/NEMS applications. Techniques such as mechanical polishing and ultrasonic seeding of the substrates have been extensively used in the synthesis of UNCD films. However, mechanical polishing can result in surface damage, and wet chemical processes require extensive cleaning after seeding. An alternative seeding process that has been used for the synthesis of microcrystalline and nanocrystalline diamond films is bias enhanced nucleation (BEN), optionally followed by bias enhanced growth (BEG), which entails exposing the substrate to a CH4/H2 plasma while electrically biasing the surface. However, it has not yet been shown that BEN and BEG can be used to produce UNCD films. The BEN-BEG process discussed in this paper involves exposure of the substrate surface to a new low-pressure and heater-assisted nucleation and growth process, using initial H2/CH4 gas chemistry followed by specific Ar/CH4 chemistry developed by our group for UNCD film growth. The BEN-BEG process discussed here produces UNCD films that exhibit simultaneously up to 93 % sp3 carbon bonding, very smooth surface (~6 nm RMS, measured by AFM), and strong adhesion to silicon substrates. High-resolution transmission electron microscopy and electron energy-loss spectroscopy were used to analyze the silicon/UNCD interface. Si (111) facets, which developed as a result of the ion bombardment during BEN, were observed, and a transition carbon-based interlayer consisting of a mixture of sp2-hybrizided C and covalently bonded Si-C was identified. This bonding structure at the interface may be the key to the strong film adhesion to the substrate. Near edge X-ray absorption fine structure spectroscopy and Raman spectroscopy revealed the high-quality sp3 bonding character and characteristic UNCD signature respectively on the top surface of the film. Some of mechanical properties (hardness, stress, and adhesion strength) will be discussed in relation to the tailored BEN/BEG/normal growth processing steps used to control internal stresses within the film.____This work was supported by the US Department of Energy, BES-Materials Sciences, under Contract DE-AC02-06CH11357.
9:00 PM - P15.37
Electrical Characteristics of Nitrogen-doped Nanocrystalline Diamond Films and Wires.
Qiang Hu 1 , Makoto Hirai 2 , Zhenqing Xu 1 , Harish Jeedigunta 3 , Ashok Kumar 1 2
1 Department of Mechanical Engineering, University of South Florida, Tampa, Florida, United States, 2 Nanomaterials and Nanomanufacturing Research Center, University of South Florida, Tampa, Florida, United States, 3 Department of Electrical Engineering, University of South Florida, Tampa, Florida, United States
Show AbstractNanocrystalline diamond (NCD) films have been extensively investigated for a number of interesting material properties, which seem to be due to their unique nanoscale morphology and electronic structures. We have recently fabricated nanocrystalline diamond wire using hybrid vapor-liquid-solid (VLS) and microwave plasma-enhanced chemical vapor deposition (MPECVD) techniques. NCD films have been also prepared on p-type Si substrates using MPECVD method. This research aims to investigate the role of nitrogen-doped NCD films and wires for electronic device applications. Electrodes of Ag colloid/Ag thin film were deposited on NCD films using shadow masking method. Electron beam lithography has been used to make metal contact for NCD wires having about 3 µm in diameter. We have made heterojunction structure consisting of N-doped NCD film on p-type Si substrate and the results of the asymmetry of the I-V curve prove that the major carrier of the N-doped NCD film is electron. This research will also discuss the results of change of conductivity of nitrogen-doped NCD wire.
9:00 PM - P15.38
Synthesis of Large Area Low Temperature Ultrananocrystalline Damond (UNCD) Films and Integration with CMOS Devices for Monolithically Integrated Diamond MEMS/NEMS-CMOS Systems.
Anirudha Sumant 1 , Orlando Auciello 2 1 , H. Yuan 3 , Jack Ma 3 , Bernd Kabius 2 , Derrick Mancini 1
1 Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois, United States, 2 Materials Science Division, Argonne National Laboratory, Argonne, Illinois, United States, 3 Department of Electrical and Computer Engineering, University of Wisconsin-Madison, Madison, Wisconsin, United States
Show AbstractBecause of exceptional mechanical, chemical, and tribological properties, diamond has a great potential to be used as a material for the development of high-performance, harsh environment-compatible devices for MEMS and NEMS, such as resonators and switches which involve mechanical motion and intermittent contact. However, such devices should be integrated with complementary metal oxide semiconductor (CMOS) microelectronics to exploit their use in CMOS-driven commercial MEMS/NEMS. The main hurdle to achieve diamond-CMOS integration is relatively high substrate temperatures (600-800 C) required for depositing conventional diamond thin films, which are well above the CMOS operating thermal budget (400 C). Additionally, a materials integration strategy has to be developed to enable diamond-CMOS integration. Ultrananocrystalline diamond (UNCD), a novel material developed in thin film form at Argonne, is the only diamond film that can be grown at 400 C, and still retain exceptional mechanical, chemical, and tribological properties comparable to that of single crystal diamond. We have developed a process based on microwave plasma CVD to synthesize UNCD films on 200 mm CMOS wafers, which will open new avenues for building CMOS-driven devices for MEMS/NEMS based on UNCD. UNCD films were grown successfully on individual Si-based CMOS chips and on 200 mm CMOS wafers at 400 C in a plasma-deposition system using microwave-plasma-enhanced chemical vapor deposition with Ar-rich/CH4 gas mixture. The CMOS devices on the wafers were characterized before and after UNCD deposition. All devices were performing to specifications with acceptable degradation after UNCD deposition and processing. A threshold voltage degradation in the range of 0.08-0.44V and transconductance degradation in the range of 1.5-17% were observed. We also report the on cross-section TEM studies of the UNCD/CMOS interface and discuss the possible mechanisms responsible for the degradation of CMOS performance.
9:00 PM - P15.39
Optimising Mono-dispersed Diamond Nanopowder Seeding for Ultrathin NCD Film Fabrication.
Soline Allard 1 , Christine Mer 1 , Milos Nesladek 1 , Samuel Saada 1 , Jean-Charles Arnault 2 , Philippe Bergonzo 1 , Oliver W. Williams 3 , Eiji Osawa 4
1 CEA-LIST, Centre d’Etudes de Saclay, Gif-Sur-Yvette France, 2 DSM-DRECAM-SPCSI, CEA (Saclay), Gif-Sur-Yvette France, 3 IMOMEC, Hasselt University, Diepenbeek Belgium, 4 , NanoCarbon Research Institute Ltd, Kashiwa Japan
Show AbstractUltra-thin diamond films are excellent candidates for thermal dissipation in electronic devices for nanoelectronic applications. However, a very high nucleation is required at the early stages of growth to be able to grow ultra-thin (<100nm) and continuous films. Recently, novel routes for nucleation have been reported as nano-seeding, and leading to densities of nucleii higher than 1011 sites /cm2. To achieve this, diamond crystals (diameter 6 nm) produced by detonation method are dispersed into a liquid solution using ultrasonic processes. The substrate surface is then seeded by immersion. The main challenges concerning nano-seeding are related to the agglomeration of diamond nanocrystals during the dispersion, the deposition methods (immersion and drying by evaporation, spin-coating, electrospray) and the homogeneity of the treatment. It is also essential to investigate the stability of nano-seeded surfaces under Microwave Plasma Chemical Vapour Deposition (MPCVD) conditions. The aim of this work is an improved control of each step (suspension, immersion and drying). The agglomeration into the suspension was studied using correlation photon spectroscopy. The density of nano-seeds and the homogeneity of the treatment were investigated using High Resolution Scanning Electron Microscopy (HRSEM). Moreover, the chemical and thermal stabilities have been studied using X-ray Photoemission Spectroscopy (XPS) after UHV thermal treatments or MPCVD exposures.
9:00 PM - P15.4
Ex Situ Spectroscopy Ellipsometry Modeling and Electrical Properties of Boron-Doped Diamond Films for Electrochemical Applications.
Ajay Dudipala 1 , O. Williams 2 , Sanju Gupta 1
1 Electrical and Computer Engineering, University of Missouri, Columbia, Missouri, United States, 2 Institute of Materials Research, Hasselt University, Diepenbeek Belgium
Show Abstract9:00 PM - P15.40
A Portable Vacuum Packaged Nanodiamond Lateral Field Emission Diode.
Weng Kang 1 , J. Davidson 1 , K. Subramanian 1
1 EECS, Vanderbilt University, Nashville, Tennessee, United States
Show AbstractVacuum microelectronic devices involving lateral-type emitters offer reduced complexity for device integration and vacuum packaging. In addition, their small interelectrode separation feature results in low voltage device operation, essential for practical microelectronic applications. The development of a vacuum package is of practical relevance to field emission devices. We report the development of a portable diamond lateral field emitter device operating in a vacuum package. Micropatterned nanodiamond lateral field emission diodes are batch fabricated on a SOI substrate using a single-mask process technique. The cathode is composed of a uniform array of nanodiamond lateral emitters, which have a high aspect-ratio “finger-like” geometry, with a sharp tip apex, radius of curvature ~ 15 nm. The nanodiamond integral anode is located laterally at a distance as small as 2 μm from the cathode, isolated by a 1 μm thick SiO2 layer beneath the electrodes. The electrodes are equipped with large contact pads for electrical probing. The die comprising the lateral devices is then attached firmly onto a 10-pin cavity package. A 40000 Å thick Ti/Au film was deposited onto the back surface of the substrate, and attached to a 1-inch square coupon of thick film gold on ceramic by using a AuSn solder preform and run through a belt furnace at ~320 °C peak temperature. Aluminum wire bonding directly onto the nanodiamond contact pads of the lateral devices is then performed. The smooth top surface morphology (8-20 nm RMS surface roughness) of nanodiamond plays a critical role in yielding a robust wire-bond. The package is finally vacuum-sealed in a STS® advanced packaging system using a getter material at a process temperature of ~360 °C. Fine and gross leak tests are performed to inspect the vacuum seal integrity. A vacuum-packaged 6-finger nanodiamond lateral diode was characterized for field emission, yielding an emission current over 3 μA at an anode voltage of 95 V (electric field: ~10 V/μm). The Fowler-Nordheim behavior showed a highly linear plot with a negative slope, confirming that the current is due to field emission from the nanodiamond lateral emitter-fingers. The electron emission was found to be stable over time at a constant applied voltage, indicating the integrity of the nanodiamond emitters and the vacuum package. The device/package was then transferred into a bell-jar vacuum chamber maintained at a base pressure of 2x10-7 Torr; the field emission (I-V) characteristics were observed to be virtually unchanged, thus verifying that the vacuum seal of the package is reliable, with no leak. The nanodiamond lateral device performance can be further improved by applying a larger emitter array with a smaller interelectrode gap. The vacuum-packaged nanodiamond lateral field emission device holds immense applicability for high-speed, extreme-environment vacuum nanoelectronics, sensors, and NEMS systems.
9:00 PM - P15.41
Role of Nucleation on the Growth of Nanocrystalline Diamond (NCD) Films: A Particular Study in the Fabrication of Micro-cantilevers.
Sathyaharish Jeedigunta 1 , Priscila Spagnol 2 , John Bumgarner 2 , Ashok Kumar 3
1 Electrical Engineering, University of South Florida, Tampa, Florida, United States, 2 , SRI International, St. Petersburg, Florida, United States, 3 Mechanical Engineering, University of South Florida, Tampa, Florida, United States
Show AbstractThe effect of nucleation by the ultrasonic scratching method on the growth of intrinsic nanocrystalline diamond films has been studied by investigating the nucleation densities of two different nanodiamond slurries- 1) nanodiamond powder suspended in acetone 2) mixture of titanium nanopowder and nanodiamond powder suspended in acetone. The former has resulted in a lower nucleation density of the order of 108 cm-2 while the later has increased the nucleation density by at least two orders (1010 cm-2) of magnitude. The nanocrystalline diamond(NCD) films were grown on mirror polished Si(100) substrates in a Cyrannus I Iplas microwave plasma enhanced chemical vapor deposition (MPECVD) reactor using 0.5 % CH4/ 1 % H2/ 98.5 % Ar gas chemistry at a substrate temperature of ~ 750° C, pressure of 135 T and a microwave power of 1.8 kW. Double anchored cantilever structures have been fabricated using NCD as structural material. It was observed that the films grown after pre-treating the substrates in pure nanodiamond slurry have not provided a complete coverage at the anchor regions of the cantilevers due to the lower nucleation density. Hence during the sacrificial oxide etch, the anchor regions did not adhere well to the substrate and the structures got detached from the sample surface. But on the other hand, the films grown by seeding the substrates in a suspension of titanium and diamond nanopowder showed complete film coverage and consequently very good bonding at the anchor pads. In this case, the cantilevers have been successfully released without any problems at the anchor pads. This is attributed to the improved nucleation density in the later case. Further study of the nucleation density effect on the mechanical properties of the films is conducted by evaluating the intrinsic stress and the Young’s modulus using an optical reflection method and nano-indentation techniques respectively.
9:00 PM - P15.42
Structural and Mechanical Properties of Nanocrystalline Diamond Wires.
Zhenqing Xu 1 2 , Ashok Kumar 1 2 , Qiang Hu 1 2 , Sathyaharish Jeedigunta 3 , Zhu- Hui Xu 4 , Xiaodong Li 4
1 Mechanical Engineering, University of South Florida, Tampa, Florida, United States, 2 Nanomaterials and Nanomanufacturing Research Center, University of South Florida, Tampa, Florida, United States, 3 Electrical Engineering, University of South Florida, Tampa, Florida, United States, 4 Mechanical Engineering, University of South Carolina, Columbia, South Carolina, United States
Show AbstractNanocrystalline diamond (NCD) combines outstanding properties of crystalline diamond with improved tribological properties due to smaller grain size (5 to 15 nm). This makes NCD as an attractive candidate for the fabrication of Nano/Micro-Electro-Mechanical Systems (NEMS/MEMS). However, until now, most of the work is related to NCD thin films. In our study, for the first time, one dimensional NCD structures have been successfully synthesized and their structural and mechanical properties have been evaluated. These NCD wires are 0.5 - 5 μm in diameter, depending on the growth time, with lengths in the range of 20 – 100 μm. The morphology and structure of these wires have been characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), near edge X-ray absorption fine structure (NEXAFS), and Raman spectroscopy. The mechanical properties of these wires were evaluated by nanoindentation tests in conjunction with an atomic force microscopy (AFM). The average elastic modulus determined using Hertz contact theory was ~ 474.16±13.48 GPa, which is ten times higher than SiO2, GaN, or Au nanowires. Such a high mechanical strength added to other inherent outstanding nature of NCD, makes these wires an ideal material for the fabrication of active components in both electronic and electromechanical devices. Moreover, the biocompatibility of NCD and the high surface to volume ratio of these one dimensional nanostructures can enhance the sensitivity and selectivity of NCD based bio-sensors and bio-devices.
9:00 PM - P15.43
Highly Oriented Diamond Film Grown at High Growth Rate.
Xianglin Li 1 , Ramon Collazo 1 , Zlatko Sitar 1
1 MSE, NCSU, Raleigh, North Carolina, United States
Show AbstractHighly oriented diamond (HOD) films (100) are commonly grown at a growth rate of 0.3 µm/hr by microwave plasma chemical vapor deposition (MPCVD) with a 1.2 kW microwave source on (100) silicon substrates. By exploring different growth parameters, HOD films with similar crystalline properties and phase purity can be grown at 4.5 µm/hr within the same growth system. The growth rate and crystalline quality were investigated as a function of total pressure employed (25-100 Torr), methane concentration in hydrogen (1.6-7%), and air concentration (30-3000 ppm). It was observed that the required air concentration for obtaining HOD is higher for higher growth rates. For a growth rate of 0.3 µm/hr, the required air concentration was 30 ppm, while for a growth rate of 4.5 µm/hr, an air concentration of 1000 ppm was needed to obtain a similar HOD morphology and crystalline quality. A detailed study of the crystalline quality as determined by X-ray diffraction texture analysis and phase purity as determined by Raman spectroscopy as a function of methane and air concentrations in hydrogen will be presented.
9:00 PM - P15.45
Hydrogen-free CVD Diamond Synthesis on Nonplanar Substrate with Liquid Carbon Source.
Mary Mikawa 1 , Tayuki Hirai 1 , Yoshimi Endo 1 , Yoshiki Takagi 1
1 , Teikyo University of Science & Technology, Uenohara-city Japan
Show AbstractIn traditional CVD (Chemical Vapor Deposition) diamond synthesis on the nonplanar substrate, such as silicon single crystal, hydrogen radicals thought to be inevitable.In this work, we synthesized diamond particles without flammable hydrogen gas for easier and safer experiments, we call “hydrogen-free diamond”.We used vaporized acetone and carbon dioxide mixture for carbon source.Partial pressures of acetone and carbon dioxide were 30 and 15 Torr, respectively.Particles with 0.5 up to 1.0 micrometer in diameter were synthesized and confirmed as diamond with SEM photographs and Raman spectroscopy.As a result, with the hot-filament CVD, diamond synthesis was possible without hydrogen gas.
9:00 PM - P15.46
CVD Diamond Applications as TL/OSL Radiation Dosimeters.
M. Barboza-Flores 1 , R. Melendrez 1 , V. Chernov 1 , M. Pedroza-Montero 1
1 Centro de Investigacion en Fisica, Universidad de Sonora, Hermosillo, Sonora, Mexico
Show AbstractThe present work presents the status of the development of synthetic diamond devices suitable for dosimetric applications. The extraordinary characteristics of chemically vapor deposited (CVD) diamond such as tissue equivalence, radiation hardness, and lack of solubility in water and sanitizing agents, makes CVD diamond a very promising material for dosimetric applications. Recent investigations have shown that CVD techniques allowed the growing of good quality diamond films in a diversity of substrates to be used in the form of ionization chambers, thermoluminescence (TL) and optically stimulated luminescence (OSL) detectors and dosimeters. Successful results have been obtained related to gamma, beta, X-rays and UV radiation. In spite of the significant results, some problems remain dealing with dose behavior and linearity, dose rate dependence and stability. Therefore, a lot of research work is necessary to improve the synthetic material characteristics to optimize the radiation dosimeter device performances.
9:00 PM - P15.48
Experimental Study on the Origin of Non-uniform Etching of Nano-crystalline Diamond during Reactive Ion Etching.
Jeung-hyun Jeong 1 , Ju-Heon Yun 1 , Jong-Keuk Park 1 , Wook-Seong Lee 1 , Young-Joon Baik 1
1 Thin Film Materials Research Center, Korea Institute of Science and Technology, Seoul Korea (the Republic of)
Show AbstractReactive ion etching (RIE) of diamond films is essential to MEMS applications such as bio MEMS, rf MEMS, stress sensor, etc and have been studied using oxygen plasma. However, oxygen plasma RIE results in very non-uniform etching of diamond surface, forming a number of nano-pillars. It is known that the formation of such nano-pillars is suppressed by adding small amount of fluorine gas such as CF4 and SF6. To our knowledge, the origin of the nano-pillars and the role of fluorine gas are still controversial. In this study, we tried to investigate the principle underlying the nano-pillar formation and F-induced suppression by comparing the etching behaviors of nano-crsytalline diamond with different quality. Different nano-crystalline diamond films were prepared by hot-filament CVD (HF diamond) and DC plasma CVD (DC diamond), and were dry-etched using a commercial ICP etcher with oxygen only plasma, SF6-added, and Cl2-added oxygen plasma. The etching behaviors were significantly different with diamond species; very fine small nano-pillars were formed on DC diamond while crude large pillars were on HF diamond. A few percentage SF6 addition did not only suppress the pillar formation, but also increased the etch rate, the effect of which were more substantial in DC diamond. Cl2 addition was not effective. Such results remove the possibility of the existence of etch masks due to etch residue or outer materials, and support that non-uniform etching is originated from the quality of the diamond. Here the nano-pillar formation will be discussed in terms of selective etching due to different grain size, sp2/sp3 ratio, surface roughness, and the role of fluorine gas.
9:00 PM - P15.49
Hemocompatibility of Diamondlike Carbon Thin Films.
Ravi Aggarwal 2 , Anand Doraiswamy 1 , Roger Narayan 1
2 Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina, United States, 1 Biomedical Engineering, University of North Carolina, Chapel Hill, North Carolina, United States
Show AbstractPolydimethylsiloxane (PDMS) is a polymeric material that is routinely used for surgical repairs and body implants. In the present work, we have investigated the processing and biocompatibility of diamond-like carbon (DLC) thin films on PDMS prepared by pulsed laser deposition process. Diamondlike carbon has been considered for use in a coronary artery stents, synthetic heart valves, left ventricular assist devices, and artificial hearts, because platelet activation and platelet adhesion occur less often on diamondlike carbon-coated surfaces than on conventional (titanium, titanium carbide, titanium nitride, or stainless steel) surfaces. Pulsed laser deposition of diamond-like carbon thin films involves ablation of a sp2 bonded carbon target at room temperature, resulting in the formation of sp3-hybridized diamond-like carbon thin film. The growth rate of diamond-like carbon films using a krypton fluoride excimer laser (wavelength=248 nm) is approximately 0.01 nm/pulse. These materials were examined using optical microscopy, scanning electron microscopy, and atomic force microscopy. The hemocompatibility of these materials was examined using bovine blood platelet rich plasma. The hameocompatibility was studied by immersing the samples in bovine platelet rich plasma. Diamond-like carbon coated polydimethylsiloxane materials may provide alternative solutions for improving the blood compatibility of implantable medical devices, including next-generation cardiovascular implants.
9:00 PM - P15.5
Application of Power Spectral Density and Autocorrelation in Analyses of Surface Roughness and Film Morphology for Boron-Doped Diamond Films.
Gregory Vierkant 1 , O. Williams 2 , Sanju Gupta 3
1 Physics and Materials Science, Missouri State University, Springfield, Missouri, United States, 2 IMR, Hasselt University, Diepenbeek Belgium, 3 Electrical and Computer Engineering, University of Missouri, Columbia, Missouri, United States
Show AbstractThe surface roughness evolution of growing thin films of metals or semiconductors provides much information about their growth mechanism. While some systems show stages of nucleation, coalescence and growth, the others exhibit varying microstructures with process conditions. In view of this classification, we report detailed analyses relating the atomic force microscopy (AFM) characterizations to extract the surface roughness and growth exponents of boron-doped diamond (BDD) films by utilizing the Power Spectral Density (PSD) and Autocorrelation Function (ACF) tools. The machining industry has applied PSD for a number of years for the tool design, wear, and machined surface quality. Hereby, we present a similar analysis at nanoscale to study the surface morphology as well as quality of BDD films grown using microwave plasma-assisted chemical vapor deposition technique. PSD spectra as a function of boron concentration (in gaseous phase) are compared with those grown without boron. We found that higher boron concentrations yielded higher amplitudes in the longer wavelength power spectral lines with amplitudes decreasing in an exponential fashion towards the shorter wavelengths determining the exponents. A unique application of the ACF function, widely used in signal processing, was applied to one-dimensional AFM surface topology data sets along the x- and y- axis, for varying boron concentrations. Here, the ACF was used to cancel random surface “noise” and identify any spatial periodicity via repetitive ACF peaks. Periodicity at shorter spatial wavelengths was observed for un-doped and low doping levels, while small correlation was observed for the higher concentration. These quantitative spatial analyses may prove useful in comparing synthesis techniques and films grown with varying compositional makeup. These findings in terms of surface and growth exponents are also correlated with traditional AFM, Raman spectroscopy (RS), and X-Ray Diffraction (XRD) analytical tools thus helping to provide an insight into the growth kinetics albeit in an inverse manner. The authors (GPV and SG) acknowledge Dr. R. Giedd (CASE, Director) for providing the AFM instrument used in this study and Mr. R. J. Patel for the AFM measurements.
9:00 PM - P15.50
Influence of Gamma Irradiation on Hydrogen-terminated Boron-doped Diamond Films.
M. Muralikiran 1 , J. Farmer 2 4 , C. Greenlief 3 , J. Robertson 3 4 , X. Han 5 , Sanju Gupta 1 4
1 Electrical and Computer Engineering, University of Missouri, Columbia, Missouri, United States, 2 Physics, University of Missouri, Columbia, Missouri, United States, 4 Research Reactor, University of Missouri, Columbia, Missouri, United States, 3 Chemistry, University of Missouri, Columbia, Missouri, United States, 5 , Brewer Sciences Inc., Rolla, Missouri, United States
Show AbstractDiamond in all forms offering multifunctionality and specifically doped diamond is of great interest owing to unsurpassable physical (mechanical, thermal, electrical, electrochemical, and biological) properties for multiple applications besides it is known for radiation hardness, and is thus preferable over other semiconductors. For ‘harsh’ radiation environment applications i.e. deep UV photodiode and nuclear micro-battery [1-3], it is critical to demonstrate materials' structural integrity and performance. Thin films of hydrogen-terminated boron-doped poly-/micro diamond (H-BDD) deposited by microwave plasma-assisted CVD with varying boron concentration ranging 100 ppm to 4000 ppm in gas phase, were submitted to gamma radiation (5, 10, and 100 Mrads). They were analyzed prior to and post-irradiation in terms of morphology, microscopic structure and physical property using SEM, AFM, Raman spectroscopy (RS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and ultraviolet photoelectron spectroscopy (UPS) to establish the property-structure-processing relationship. Interestingly, we did not observe dramatic changes in their structural characteristics with increasing radiation dose in contrast to un-doped non-hydrogenated diamond as reported earlier [4], alluding to the stability of H-BDD films. A possible explanation is proposed: BDD is conductive throughout, H-terminated diamond is conductive on the surface, but non-H terminated diamond is insulating. The gamma photons create electron-hole (e-h) pairs and charge redistribution in the material, which is stage one of damage. But stage two of damage occurs when these particles (e-h pairs) fly apart at high energy and suffer more collisions with the lattice. The hole, especially, may collide with a bonding electron and mutually annihilate, leaving a weakened or broken bond behind. In a conducting material the e-h pairs are not so localized, and travel through the lattice much further distances before colliding, thus suppressing defect enhancement which may occur due to recombination. This would spread or smear out any damage effects and make it appear less severe. In addition, the UPS measurements yielded a slight increase in electron affinity from 0.42 to 0.74 eV for all of the BDD films with increasing gamma irradiation pointing at the decrease in surface conductivity, albeit small, which corroborates with microscopic structure properties. *The author (SG) acknowledges Dr. O. Williams (IMR, Belgium) for H-BDD samples and Dr. P. May (Bristol University, UK) for useful discussions. This work is financially supported in part by MURPI and MURFA funds administered by the University of Missouri Research Reactor (MURR).[1] M. Murali, et. al., MAS conference Apr. 20-21, 2007, (Senior Division, Oral Presentation).[2] M. Liao et. al., Appl. Phys. Lett. 88, 033504 (2006).[3] C. J. Eiting, et. al., Appl. Phys. Lett. 88, 064101 (2006). [4] S. Gupta, et. al. J. Appl. Phys. 92, 3311 (2002).
9:00 PM - P15.51
Ion Implantation Damage and Amorphization in HPHT Single Crystal Diamond: A TEM Study.
Diane Hickey 1 , K. Jones 1 , R. Elliman 1
1 , University of Florida, Gainesville, Florida, United States
Show AbstractIon implantation into single-crystal high-pressure-high-temperature diamonds was explored using transmission electron microscopy (TEM). The recovery of the diamond lattice after implantation and annealing was studied in both (001)- and (011)-oriented diamond substrates Si+ implanted at 1 MeV to a doses of 1 × 1014 and 1 × 1015 cm-2 at 303K. The effect of implant temperature, comparing room (303 K) to liquid nitrogen (77 K) temperature, revealed upon annealing that the lower temperature implant formed pockets of amorphous material in the projected range, while the higher temperature implant did not. Ion implantation induced amorphization was also explored. A buried marker layer was created by implanting Si+ at 2 MeV to a dose of 1 × 1015 cm-2 at 77K. Subsequently, a buried amorphous layer was created by using a second Si+ implant at lower energy (1 MeV) and higher dose (7 × 1015 cm-2) at 303K. The amorphous carbon layer caused the diamond surface to swell approximately 150 nm, as determined by cross-sectional TEM. The implantation-induced amorphous layer was 25% less dense than diamond, and 15% more dense than graphite. Comparison with the Monte Carlo simulations suggest the critical displacement threshold for amorphization of diamond is approximately 6 ±2 ×1022 vacancies cm-3. HRTEM shows no evidence of crystalline graphite in the amorphous later.
9:00 PM - P15.6
Electron Transfer from a Diamond 100 Surface to an Atmospheric Water Adlayer: A Quantum Mechanical Study.
Daniel Petrini 1 , Karin Larsson 1
1 , Material Chemistry, Uppsala Sweden
Show Abstract9:00 PM - P15.8
Synthesis of Nanocrystalline Hexagonal Diamond Films in Organic Solvents by Femtosecond Laser Irradiation.
Anming Hu 1 , Walt Duley 1
1 Department of Physics, University of Waterloo, Waterloo, Ontario, Canada
Show AbstractDiamond-like films have been synthesized on various substrates by irradiation of a variety of organic solvents including acetone, pentane, hexane, heptanes, octane, dodecane, and hexadecane in the presence of transition metal as the catalyst near the laser focus under atmosphere pressure with intense 800 nm femtosecond laser pulses. Vis-Raman spectra display a strong vibration mode at 1308 cm-1 characteristic of hexagonal diamond. X-ray photoelectron spectra confirm that the film is mainly sp3-bonded carbon containing a low concentration of sp2-bonded inclusions. Film microstructure shows that these films are assembled from nanoparticles having an average size of < 100 nm. The sp3 / sp2 ratio is found to depend on the type of substrate and is highest for deposition on Fe. Intermediate values for this ratio are found for deposition on Co and Ni and the lowest value is obtained on Cu. With Fe, rhomobohedral Fe2O3 nanoparticles are found near the irradiation site. Analysis of the liquid after irradiation using HPLC techniques indicates that polyyne molecules are synthesized during irradiation. It appears that these molecules are precursors for the formation of hexagonal diamond. As the yield of polyyne molecules is found to exhibit a non-linear relation to laser intensity, it is possible that these species are formed as the products of ion chemistry following Coulomb explosion. This process may enable a new method for the creation of nanocrystalline hexagonal diamond layers for micro-electronic and other applications.
9:00 PM - P15.9
Phonons and Electron-phonon Coupling in Heavily Boron-doped Diamond Epilayers: a Combined Study by Inelastic X-ray Scattering and Second Order Raman Scattering.
Etienne Bustarret 1 , Philipp Achatz 1 2 , Franck Omnes 1 , Moritz Hoesch 3 , Jorge Serrano 3 , Michael Krisch 3
1 Institut Néel, CNRS, Grenoble France, 2 DRFMC, CEA, Grenoble France, 3 , ESRF, Grenoble France
Show AbstractA series of B-doped films with thicknesses ranging from 1 to 30 µm were grown on (100)-oriented Ib diamond substrates by MPCVD in a B2H6/CH4/H2 mixture. Low Temperature transport measurements showed that their behaviour ranged from insulating to both metallic and superconducting, depending on the boron contents (from 1 1020 to 5 1021 at/cm3). These films were analysed by first order and second order Raman Scattering Spectroscopy at various excitations wavelengths and the phonon softening (at the Brillouin zone center and at some zone boundary critical points) were determined as a function of the doping level. The results show that this softening is much less pronounced (a factor of three in the frequency red shift) than expected theoretically from the Virtual Crystal Approximation, and in reasonable agreement with supercell calculations. In the particular case of the optical branch, these results were confirmed by Inelastic X-ray Scattering experiments on some of the thicker samples. A quantitative analysis of both the linewidth and the spectral shifts yielded some estimates of the electron-phonon coupling for such modes. The values are compared to those inferred from other measurements as well as to those resulting from supercell calculations.