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