Symposium Organizers
Philippe Bergonzo CEA-LIST
Commissariat Energie Atomique (CEA/Saclay)
James E. Butler (Retired from Naval Research Laboratory)
Christoph E. Nebel Fraunhofer Institut fuer Angewandte Festkoerperphysik
Andrew T. S. Wee National University of Singapore
Milos Nesladek Hasselt University & IMEC vzw
A5: Poster Session: Diamond Electronics and Bioelectronics
Session Chairs
Tuesday AM, November 30, 2010
Exhibition Hall D (Hynes)
A1: Novel Imaging Approaches with Single Photon Sources
Session Chairs
Monday PM, November 29, 2010
Room 306 (Hynes)
9:30 AM - **A1.1
Nanoscopy With Focused Light.
Stefan Hell 1
1 Dept. of NanoBiophotonics, Max-Planck-Institute for Biophysical Chemistry, Göttingen Germany
Show AbstractIt has been generally accepted that the resolution of a lens-based optical microscope is limited to about > 200 nm in the focal plane and > 500 nm along the optic axis, with NA denoting the numerical aperture of the lens and the wavelength of light. The discovery in the 1990’s that elementary transitions between the states of a fluorophore can be used to eliminate the limiting role of diffraction has led to light microscopy concepts with resolution on the nanometer scale. Currently, all existing and successfully applied nanoscopy methods share a common enabling element: they switch fluorescence on or off, so that adjacent features are registered sequentially in time.For example, in a typical Stimulated Emission Depletion (STED) microscope, the fluorophores are switched off (=kept dark) by overlapping the excitation beam with a de-exciting (STED) beam which effectively confines the fluorophores to the ground state everywhere in the focal region except at a tiny area where the STED beam is close to zero. Fluorophores that are located in this subdiffraction-sized smaller area are registered. Scanning the beams further in space registers those fluorophores that had been switched off. An image of the whole object is assembled by sequential registration. The resolution is now given by the smaller diameter d of this area in which the fluorophores are still fluorescent. I is the intensity of the STED beam, which, for I >> Is, entails d→0, meaning that the resolution is conceptually no longer limited by lamda.STED microscopy has been used to investigate the fate of synaptic vesicle proteins after exocytosis, thus demonstrating the potential of emerging ‘fluorescence nanoscopy’ for the life sciences. A video-rate STED microscope was used to describe the mobility of vesicles inside the axons of cultured living neurons. Live-cell STED microscopy has also been used to image activity-dependent morphological plasticity of dendritic spines, while in another study, it revealed that single sphingolipids, but not phospholipids, are transiently (< 10 ms) and locally (< 20 nm) trapped in a living cell membrane, mediated by cholesterol.The concept of STED microscopy has been expanded to low intensity operation by switching the fluorophore to a long-lived dark (triplet) state or between a ‘fluorescence activated’ and a ‘deactivated’ (conformational) state as encountered in switchable fluorescent proteins. More recent but seminal nanoscopy schemes such as PALM, STORM and also GSDIM, switch the molecules individually and stochastically to a state that emits m >>1 detectable photons in a row before returning to a dark state, allowing the calculation of their position. Altogether, lens-based optical nanoscopy is an unexpected and fascinating development in the physical sciences that is poised to impact several areas of science, in particular the life sciences, in the near future.
10:00 AM - A1.2
Photoluminescent Diamond Nanoparticles for Cellular Super-resolution Imaging.
Marie-Pierre Adam 1 , Yan-Kai Tzeng 2 1 , Jacques Botsoa 1 , Orestis Faklaris 2 , Hugues Girard 3 , Geraldine Dantelle 4 , Jean-Charles Arnault 3 , Michel Simonneau 5 , Huan-Cheng Chang 2 , Francois Treussart 1
1 Laboratoire de Photonique Quantique et Moléculaire, CNRS UMR 8537, Ecole Normale Supérieure de Cachan, Cachan France, 2 Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei Taiwan, 3 Diamond Sensor Laboratory, CEA-LIST, Gif-sur-Yvette France, 4 Laboratoire de la Matière Condensée, CNRS UMR 7643, Ecole Polytechnique, Palaiseau France, 5 Université Paris Descartes, INSERM U894, Centre de Psychiatrie et Neurosciences, Paris France
Show AbstractNitrogen-Vacancy (NV) color center in diamond has a perfectly stable photoluminescence in the red and near infrared spectral region.Diamond nanoparticles (size~20 nm) containing NV color centers (fluorescent NanoDiamonds, fNDs) are therefore perfectly suited for cellular and tissues imaging in this low absorption window, and for long-term tracking.We will show that fNDs are spontaneously internalized in different cell lines including primary neurons and do not induce cytotoxicity even at high concentrations.Thanks to NV center perfect photostability, fNDs are ideal for STimulated Emission Depletion Microscopy (STED) super-resolution microscopy which requires the combination of the fluorescence excitation by a usual Gaussian intensity shape beam (wavelength 532 nm) with the high power STED beam having a doughnut shaped intensity to stimulate the emission efficiently from the excited state (wavelength 735 nm). We will present preliminary observations of super-resolution imaging of fNDs in cells using cw lasers.Such super-resolution microscopy will be used in particular to image neuronal dendritic spines morphology, which disorders are associated to numerous neurodegenerative diseases.
10:15 AM - **A1.3
Imaging Magnetic Fields Using NV Centers in Diamond.
Amir Yacoby 1
1 , Harvard University, Cambridge, Massachusetts, United States
Show AbstractDetection of weak magnetic fields with nanoscale spatial resolution is an outstanding problem in the biological and physical sciences. For example, at a distance of 10 nm, the spin of a single electron produces a magnetic field of about 1 micro Tesla, and the corresponding field from a single proton is a few nano Tesla. A sensor able to detect such magnetic fields with nanometer spatial resolution would enable powerful applications, ranging from the detection of magnetic resonance signals from individual electrons or nuclear spins in complex biological molecules to readout of classical or quantum bits of information encoded in an electron or nuclear spin memory. Recently we experimentally demonstrated an approach to such nanoscale magnetic sensing, using coherent manipulation of an individual electronic spin qubit associated with a nitrogen-vacancy impurity in diamond at room temperature. Using an ultra-pure diamond sample, we achieve detection of 30 nT magnetic fields at kilohertz frequencies after 1s of averaging. In this talk I will review some of the recent advances in the development of such a scanning magnetometer.
10:45 AM - A1.4
Optical Characterization of Diamond Nanoparticles on Transparent Thin Films and Their Applications.
Jennifer Choy 1 , Osman Bakr 1 2 , Thomas Babinec 1 , Birgit Hausmann 1 , Parag Deotare 1 , Marko Loncar 1
1 School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, United States, 2 Department of Materials Science and Engineering, King Abdullah University of Science and Technology, Thuwal Saudi Arabia
Show AbstractChemically synthesized nanoparticles, such as fluorescent dyes and colloidal quantum dots, are commonly used as nanoprobes for biological and chemical sensing applications and single photon emitters in integrated optical devices. More recently, diamond nanoparticles (DNPs) have emerged as promising candidates for these applications, owing to their excellent physical and chemical properties, which include structural stability, chemical inertness, optical transparency, biocompatibility, and surface functionalizability. Additionally, DNPs can be made optically active by the host of color centers from defects in diamond that arise either naturally or via implantation. The fluorescence from DNPs is stable at room temperature and can have wavelengths from the green to the infrared. We present results on the optical characterization of size-controlled DNPs containing the nitrogen-vacancy (NV) defect center. DNPs from commercially obtained diamond slurries have been purified and size separated using analytical ultracentrifugation, resulting in narrow size distributions of ±13nm. As demonstration of their remarkable photo- and structural stabilities in chemical sensing applications, we have subjected the DNPs to harsh chemical and physical conditions, i.e. boiling in brine, and shown that their morphology, size distribution, and luminescence remain unchanged.Meanwhile, we propose the use of DNPs containing single NV centers as ideal single photon emitters for coupling to passive optical resonators fabricated in transparent thin films such as titania. We have designed high Q/V titania nanobeam cavities (with theoretical Q ~ 10^6 and V~0.4(λ/n)^3) that operate near the zero phonon line (637 nm) of the NV fluorescence and fabricated these structures in sputtered titania, using electron beam lithography and reactive ion etching. Finally, we have studied the optical and charge transfer dynamics of various nanoparticles integrated with titania thin films, by measuring the spectra and time traces of single emitter fluorescence using confocal microscopy. In contrast to CdSe/ZnS quantum dots, which exhibit photobleaching and blinking behavior with prolonged dark states that are consistent with the transfer of charges into the lower bandgap titania host matrix, fluorescence from DNPs are stable and non-blinking.
A2: Surface Chemistry: From Diamond to Nanodiamonds
Session Chairs
Monday PM, November 29, 2010
Room 306 (Hynes)
11:30 AM - A2.1
Chemical Reactivity of Diamond Surfaces.
Phillip John 1 , Michael Anderson 1 , John Wilson 1
1 School of Engineering & Physical Sciences, Heriot-Watt University, Edinburgh United Kingdom
Show AbstractDevelopment of the next generation of diamond devices for chemical and biological sensing requires techniques for surface modification under ambient conditions. Single crystal (100) substrates have been treated with a hydrogen plasma to maximise the (100) terrace width and produce high quality surfaces. Thermal oxidation, in dry O2, yielded monolayer oxygen coverage with a high proportion of 'on-top' (>C=O)oxygen.Covalent binding of 4-trifluoromethylbenzylamine, in solution at room temperature, to the surface carbonyl group was accomplished to form the water sensitive imine bond. Reductive animation created a water stable amine functional group on the diamond (100) surface.
11:45 AM - A2.2
Surface Chemistry Control and New Routes for Fast and Stable Functionalization of Nanodiamonds.
Hugues Girard 1 , Tristan Petit 1 , Sandrine Perruchas 2 , Jean Charles Arnault 1 , Philippe Bergonzo 1
1 Diamond Sensors Laboratory, CEA LIST, Gif sur Yvette France, 2 Laboratoire de Physique de la Matière Condensée, CNRS - Ecole Polytechnique, Palaiseau France
Show AbstractFluorescent diamond nanoparticles (fNDs) carrying nitrogen-vacancy (N-V) colored centers hold great promises for biomedical applications [1]. They combine some of the outstanding properties of bulk diamond, such as the chemical resilience or the carbon surface chemistry, as well as the benefits of a fluorescent center emitting in the far-red with an ultrahigh photostability [2]. Furthermore, their low cytotoxicity is reported [3] and their mass production is now well controlled [4].The use of fNDs to label biomolecules and track their fate in-vivo or to deliver bioactive molecules implies the addition of specific functionalities to the bare fNDs. Stability in biological media, targeting or drug-release mechanisms go through a surface functionalization of the particles with, e.g. PEG chains, proteins, ionic moieties... However, after post-synthesis purifications treatments and irradiation/annealing steps to create N-V centers, fNDs surface chemistry remains highly inhomogeneous, with amorphous carbon, graphite shells and various oxidized terminations. Here we report on the chemical preparation of NDs. Methods for surface homogenization by exposures to reactive atmospheres (plasma treatments, annealings) in order to rationalize the surface chemistry are detailed. Then, new functionalization routes are proposed as efficient ways to bind bioactive molecules on these pre-treated fNDs. The surface modifications of the NDs are characterized using X-ray Photoelectron Spectroscopy, Auger electron Spectroscopy, Fourier Transformed Infra-Red Spectroscopy, Dynamic Light Scattering and Zeta Potential measurements. By our preparation and grafting methods, novel surface properties are given to NDs, such as e.g. cationic sites, self-adhesive spots, useful for biomedical applications.[1]A. M. Schrand et al., Crit. Rev. Sol. State, 34 (2009) 18[2]S.-J. Yu et al., J. Am. Chem. Soc., 127 (2005) 17604[3]V. Vaijayanthimala et al., Nanotechnol., 20 (2009) 425103[4]Y.-R. Chang et al., Nanotechnol., 3 (2008) 284
12:00 PM - A2.3
Enhanced Reactivity of Diamond Nano-particles.
Oliver Williams 1 , Jakob Hees 1 , Christoph Nebel 1
1 Micro & Nano-sensors, Fraunhofer IAF, Freiburg Germany
Show AbstractNano-diamond particles obtained from the purification of detonation products are found tightly aggregated and with a diverse array of contaminants. This aggregation is due to sp2 carbon shells which are formed during the cooling cycle of the detonation shock wave. The de-aggregation of such material is difficult and various techniques have been proposed each with their relative merits and flaws. For example, milling techniques based on zirconia beads result in significant contamination while burning in air results in substantial material loss. In this work we present a complimentary technique based on the surface shell reactivity of these particles that has none of the above drawbacks.By heating detonation nano-diamond particles in hydrogen gas at 500 °C (10 mbar, 5 hours), we are able to produce mono-disperse colloids with particle sizes between 3-4 nm. The zeta potential of these colloids changes from negative for the untreated particles to positive for the treated material. The negative zeta potential originates from acidic groups on the untreated product that are displaced by hydrogen in the treated material. The change in zeta potential and particle size demonstrates that the particle surfaces are able to react with molecular hydrogen at relatively low temperatures. This is due to the sp2 nature of the surfaces which we have confirmed with TEM and analogous experiments on carbon black. Positive zeta potentials are a common feature of hydrogenated carbon black and larger diamond particles with less sp2 do not show this effect. Thus, we conclude that the effect is based on the sp2 nature of the detonation nano-diamond surfaces.
12:15 PM - A2.4
Predicted Site Dependence of the Binding Energies of Amino and Carboxylic Acid Groups on Diamond Nanoparticles: A New Route for Multi-functionalization.
Zachary Fitzgerald 1 , Natalie Gibson 1 , Tzy-Jiun Mark Luo 1 , Olga Shenderova 2 , Donald Brenner 1
1 Material Science, North Carolina State University, Raleigh, North Carolina, United States, 2 , International Technology Center, Research Triangle Park, North Carolina, United States
Show AbstractThe facile surface chemistry of diamond nanoparticles with a variety of different functional groups has made these systems attractive for many different applications in the materials and bio-medical sciences. To better understand and predict the covalent bonding of surface species to diamond nanoparticles, we have been using a semi-empirical electronic method to calculate surface binding energies for –NH2 and -COOH groups on hydrogen terminated 4.5 nm octahedral diamond nanoparticles as a function of binding site. The calculations predict that both functional groups prefer binding at apex sites, followed by edge and then terrace sites. For the amino group, the energy difference between bonding to an apex and edge site is ~0.3 eV, while the difference between the edge and terrace site is only ~0.1 eV. The energy difference between the apex and edge sites for the carboxylic acid group is also ~0.3 eV, but the energy difference between the edge and terrace site is ~0.7 eV. The differences in binding energies between the different sites are attributed to geometric effects that reduce steric repulsion between the functional groups and surface hydrogen for the apex and edge sites compared to the terrace sites. The larger difference in binding energy between the edge and terrace sites for the carboxylic acid compared to the amino group is attributed to the larger size of the former. This prediction of a relatively large dependence of binding energy on binding site suggests very different thermal lifetimes of these sites, and the possibility of using thermal cycling in different plasma environments to create nanoparticles with spatially heterogeneous chemical activity. Results of Monte Carlo simulations intended to test this hypothesis will be presented.
12:30 PM - A2.5
Nanodiamond Polymer Composites.
Ioannis Neitzel 1 , Mary Sullivan 2 , Vadym Mochalin 1 , Giuseppe Palmese 2 , Yury Gogotsi 1
1 Materials Engineering, Drexel University, Philadelphia, Pennsylvania, United States, 2 Chemical Engineering, Drexel University, Philadelphia, Pennsylvania, United States
Show AbstractNanodiamond powder (ND) produced by detonation on an industrial scale is an attractive nanomaterial for reinforcing polymer matrices due to its superior mechanical, thermal and chemical properties. Composite materials are widely used for industrial and consumer applications ranging from the aerospace industry to electronic and biomedical applications. Specifically, desirable mechanical properties of the composite materials in combination with low specific weight can lead to an increased performance and fuel economy, which are major issues in the modern economy. Therefore, there exists an ongoing interest in creating composites which are stronger and lighter than pure polymers or metals. A careful selection of the composite components is of importance to achieve the desired properties. Nanodiamond is an excellent candidate for reinforcing polymer matrices due to its unique properties. Combined with a variety of chemical functionalizations, made possible due to a presence of a large number of functional groups on its surface, this material can be tailored to engineer new composites with enhanced mechanical properties. In this study, ND has been incorporated into an epoxy matrix. High concentration (up to 50%) ND samples have been produced using hot pressing and tested by depth sensing indentation with a spherical diamond indenter. An increase of up to 350% in Young’s modulus has been observed as well as an increase in hardness of up to 300% percent as compared to neat epoxy. Also, scratch tests show a significant increase in wear resistance of the composite were both piled-up and the amount of removed material have been reduced by 50%. Additionally thermal conductivity of ND epoxy samples with concentration of 30wt. % or higher has been improved. Both mechanical and thermal conductivity data suggest the formation of an interconnected network of ND particles. To further improve mechanical properties at low concentrations of ND, research on surface functionalization of ND is ongoing.
12:45 PM - A2.6
Surface Electronic Properties of Nanodiamonds.
Joseph Welch 1 , Aysha Chaudhary 1 , Mose Bevilacqua 1 , Richard Jackman 1
1 London Centre for Nanotechnology, University College London, London United Kingdom
Show AbstractThe electrical properties of as deposited mono-dispersed detonation nanodiamonds(DNDs) have been studied; a resistivity of the order of 1012 Ω/sq has beendetermined, with only one significant conduction pathway being observed. The dielectric character of the DND particles is also good, with dielectric loss tangent values in the range 0.05-0.5 being recorded. These combined observations suggest DNDs behave in electrical terms similar to thin film diamond, and that electrical applications for DNDs are worthy of pursuit. Since a simple room temperature sonication process has been used for their deposition, coating a wide-range of three dimensional substrate materials will be possible. A limitation on the electrical use the mono-dispersed DNDs, at least in the untreated, as-deposited from solution form used here, is the catastrophic loss of diamond-like character at temperatures above 400C. In contrast H-terminated NDs show greater stability and strongly modified electrical characteristics. The results be discussed in terms of the surface electrical characteristics of this interesting form of diamond.
A3: Progress in CVD Diamond Growth
Session Chairs
Monday PM, November 29, 2010
Room 306 (Hynes)
2:30 PM - **A3.1
Routes Towards Large Area, Low Pressure Nanodiamond Growth via Pulsed MW-linear Antenna Plasma-chemistry.
Michael Liehr 1 , Frantisek Fendrych 2 , Andy Taylor 2
1 , Leybold Optics GmbH, Alzenau, Siemensstrasse 88 D-63755, Germany, 2 , Institute of Physics, Academy Sciences of the Czech Republic, Praha 8 Czechia
Show AbstractCurrent experimental configurations for MW PECVD diamond growth do not allow simple up-scaling towards large areas, which is essential for microelectronic industries and other applications. Another important issue is the reduction of the substrate temperature during diamond growth to enhance the compatibility with wafer processing technologies. Such advantages are provided by MW-Linear Antenna (LA) plasma applicators, allowing a scalable concept for diamond growing plasmas. In the present work we introduce a novel construction of LA MW applicators designed for nanodiamond growth by using plasmas ranging from continuous wave (CW) to pulsed modes of high repetition rates (up to 20 kHz).Using fast pulsing provides several advantages for diamond growth. Firstly, it allows the application of high power in short pulses, leading to non-linear MW absorption and consequently a reduction of total average input power to ~ 5W/cm2 compared to ~ 20 W/cm2 for CW LA-MWs or to typically 100-200W /cm2 for resonance cavity applicators. Despite the factor of 50 power reduction, the diamond growth rate that can be obtained at 450°C is comparable to or higher than that of resonance cavity systems. Secondly, the pulsed plasma concept brings improvements in diamond quality when compared to the CW mode. The resulting diamond films, grown by pulsed plasma, show clean grain boundaries with columnar growth, i.e. resembling classical nano-crystalline diamond (NCD) films of high crystallinity. This is achieved by the use of a tailored plasma chemistry. In fact the concentration of atomic hydrogen can be sustained with sufficiently high values during the power-off periods at the right pulse frequency, while the growth rates in the off-period is significantly reduced. This allows suppression of re-nucleation during the growth and preparation of high quality NCD films with 2-5% sp2 carbon (based on Raman measurements), for layer thicknesses ranging from 30 to 300 nm. We show how diamond quality, measured by Raman spectroscopy and by ellipsometry depends on the MW pulse frequency and CH4/CO2/H2 gas ratios. The plasma conditions are monitored by OES spectroscopy and by using plasma probing to measure the electron fluxes and the electron energy distribution function. We demonstrate highly uniform diamond films grown on Si wafers with a homogeneity < 5% over an 8 inch area.
3:00 PM - A3.2
Simulations of CVD Diamond Film Growth Using a Kinetic Monte Carlo Model: Further Insights into the Diamond Growth Process.
Paul May 1 , Jeremy Harvey 1 , Neil Allan 1 , Yuri Mankelevich 2
1 School of Chemistry, University of Bristol, Bristol United Kingdom, 2 Skobel’tsyn Institute of Nuclear Physics, Moscow State University, Moscow Russian Federation
Show AbstractKinetic Monte Carlo (KMC) simulations of CVD diamond growth have been used to simulate 300 atomic layers of diamond growth. We have previously used this model to gain insight into the fundamental processes, including adsorption, surface migration, beta-scission and etching, that govern CVD diamond growth for a fixed set of deposition conditions. We now report new results obtained from using this model to predict the growth rates and morphology expected from gas phase conditions that experimentally give rise to single crystal diamond (SCD), microcrystalline diamond (MCD), nanocrystalline diamond (NCD) and ultrananocrystalline diamond (UNCD) films. Despite its simplicity, the KMC model predicts growth rates and surface roughness values for each of the diamond types that are consistent with experimental observations. The relative rates of surface H abstraction and hopping determine the average surface diffusion length, λ, and (in the absence of defect formation and renucleation) this is a key parameter in controlling surface morphology. When the hopping rate is more than ~100× greater than the H abstraction rate, λ becomes <2, which means that migration is limited by the lack of availability of surface radical sites, and the migrating surface species simply hop back and forth between 2 adjacent sites but do not travel far beyond their initial adsorption site. Thus, Eley-Rideal processes dominate the growth, leading to the rough surfaces seen in NCD and UNCD. Conversely, when the hopping rate <100× higher than the H abstraction rate, migration occurs over greater distances (λ > 2), leading to Langmuir-Hinshelwood processes dominating the growth producing the smoother surfaces of MCD and SCD. By extrapolation, we predict that atomically smooth surfaces over large areas should occur once migrating species can travel ~5 sites (λ = 5), which requires a gas-phase concentration ratio of [H]/[CHx] > 13400 at the growing surface. Finally, the predictions for UNCD deposition in a microwave system were found to be anomalous compared to all the other growth conditions, probably as a result of carbonaceous particulates being created in the plasma which affect the gas chemistry in unknown ways.
3:15 PM - A3.3
Effect of Substrate Dislocations on Diamond Epilayer Devices Properties.
Thu Nhi Tran Thi 1 , Julien Pernot 1 , Franck Omnes 1 , Pierre Muret 1 , Etienne Gheeraert 1 , Bruno Fernandez 1 , Etienne Bustarret 1 , Jurgen Hartwig 2 , Francois Jomard 3 , Daniel Araujo 4
1 , Institut Néel, CNRS and Université Joseph Fourier, BP 166, F-38042 Grenoble Cedex 9 France, 2 , European Synchrotron Radiation Facility (ESRF), 38043 Grenoble Cedex 9 France, 3 , GEMaC –CNRS Université de Versailles , BSaint-Quentin F-92195 Meudon Cedex France, 4 , Departamento de Ciencia de los Materiales e IM y QI, Universidad de Cadiz, 11510 Puerto Rea Spain
Show AbstractOne (100) Ib HPHT substrate of 3x3mm2 was selected among 30 substrates checked by different methods such as mis-orientation, optical profiling and AFM for surface quality and bi-refringence optical microscopy and X-ray topography images for bulk quality. By optimizing MPCVD growth conditions using oxygen in the gas phase, we were able to obtain a very low boron doped layer with a smooth surface. The RMS roughness was ~2nm, similar to the substrate before growth.
Different Hall bars were fabricated on different areas on the sample in order to determine the location of defects (which come from the substrate) influencing to the devices. The high hole mobility, measured by the Hall effect, is 1250cm2/Vs at 300K, close to the highest value reported. From fitting the neutrality equation, we deduce the low boron doping level to be 5×1016cm-3 and that there is a low contribution of scattered ionized impurities around room temperature due to the low compensation. Various mobility and resistivity parameters showed inhomogeneous electrical properties. The low mobility regions of the sample correlated with high dislocation density regions as measured by X-Ray topography and high band A luminescence mapping via CL. The TEM revealed more details about the types of defect as well as their density.
In the less defective regions of the same sample (as shown by XRay topography), in order to investigate the reproducibility of Schottky diodes, we fabricated a number of planar diodes. We used two different methods to fabricate diodes: the classic ring-shape performed by O2 microwave plasma with Al contacts and the more recent method performed by ozone treatment and with Au contacts. The I(V) and C(V) characteristics showed no dependence on the treatments but rather on the dislocations density. By I(V) measurements, a forward current density of 3×10-3 A/cm2 and a reverse current density of 5x10-5 A/cm2 at ±10V are observed. The doping profiles deduced from C(V) data of these diodes give the boron concentrations in the range of 3 to 5×1016 cm-3 for all the diodes, compatible with the value of 1.3×1016 cm-3 found from the bound exciton relative intensity obtained by CL measurements and 2 to 3×1016 cm-3 obtained from SIMS measurements.
All these results confirm our success in growing homoepitaxial lightly boron doped diamond layer with its interesting electrical properties. We were able to control a low boron doping level using oxygen during MPCVD. Due to this low doping level, the electrical properties of the epilayer are sensitive to non-homogeneity of defects. The effects of dislocation in the substrate and of growth defects on device properties will be discussed in particular.
3:30 PM - A3.4
Carrier lifetime, Diffusion Length and Mobility in (100) CVD Diamond Samples Pre-treated in an O2/H2-plasma.
Wim Deferme 1 , Ken Haenen 1 2 , Milos Nesladek 1 2 , Tadas Malinauskas 3 , Kestutis Jarasiunas 3
1 Institute for Materials Research (IMO), Hasselt University, Diepenbeek Belgium, 2 IMEC vzw, Division IMOMEC, Diepenbeek Belgium, 3 Institute of Applied Research, Vilnius University, Vilnius Lithuania
Show AbstractGreat advances in the deposition of high-quality homoepitaxial diamond and their commercial availability make this material interesting for detector and device applications. An important aspect of the growth is the diamond quality improvement with the thickness, related to the coalescence of individual growth sectors and the suppression of the propagation of some dislocations in the initial stage of the growth. Hence, it is interesting to know how defects (intrinsic and extrinsic) related to the initial stage of the growth influence the charge carrier parameters – their mobility and lifetime.In this work, samples are first pre-treated in an O2/H2-plasma for different times influencing the occurence of defects like unepitaxial crystals, hillocks with flat top and pyramidal hillocks at the surface after growth of 100-500μm thick diamond layers [1,2]. While the surface is studied by SEM and AFM, LITG (Light Induced Transient Grating Technique) and ToF (Time-of-Flight) studies will give information on the carrier lifetime, diffusion length and mobility of the grown layers [3,4]. It is shown that after an O2/H2-plasma treatment of more than 3 hours, the incorporation of defects in the bulk of the grown diamond is largely reduced, which influences the carrier dynamics measured by LITG and ToF. Also the surface roughness and the growth rate are influenced by the O2/H2-plasma pre-treatment as is shown by SEM and AFM. [1] J. Achard, F. Silva, O. Brinza, X. Bonnin, V. Mille, R. Issaoui, M. Kasu, A. Gicquel, phys. stat. sol. (a) 206/9 (2009), 1949[2] G. Bogdan, M. Nesládek, J. D’Haen, J. Maes, V.V. Moshchalkov, K. Haenen, M. D’Olieslaeger, phys. status solidi (a) 202/11 (2005), 2066[3] T. Malinauskas, K. Jarasiunas, E. Ivakin, V. Ralchenko, A. Gontar, S. Ivakhnenko, Diamond Rel. Mater. 17 (2008), 1212[4] W. Deferme, A. Bogdan, G. Bogdan, K. Haenen, W. De Ceuninck, M. Nesládek, phys. stat. sol. (a) 204/9 (2007), 3017
A4: Carbon Structure: From Graphene to Diamondoids
Session Chairs
Monday PM, November 29, 2010
Room 306 (Hynes)
4:15 PM - **A4.1
Electrical Properties of the Diamond-graphene Interface.
Kian Ping Loh 1 , Priscilla Kai Lian Ang 1
1 Chemistry, National University of Singapore, Singapore Singapore
Show AbstractGraphene is a metallic conductor and diamond is an insulator. The marriage of the two materials at the interface creates interesting chemistry. In this talk, i will discuss how graphene can be transfered onto nominally undoped diamond surfaces that have been pre-treated differently (eg. H-plasma treated, O-plasma, molecular wire-coupled and UV-treated), focusing on the charge transfer and field effect mobility of the graphene on the diamond. It is found that depending on the surface terminations on diamond, the residual impurities and mobility on graphene is affected. The mechanical robustness of the graphene which is transfered to diamond is enhanced signifcantly, compared to silicon, when subjected to sonochemical agitation.
4:45 PM - **A4.2
Raman Spectroscopy as a Probe of Carbon Materials.
Mildred Dresselhaus 1
1 EECS and Physics, MIT, Cambridge, Massachusetts, United States
Show AbstractRaman Spectroscopy has been used for several decades as a probe for the structure and properties of the various types of carbon materials including both sp3 diamond materials and sp2 planar carbon materials. We include here a discussion of nanostructured forms like nanodiamond, nanotubes, fullerenes, and graphene-like materials. Insights into our present knowledge of the field and open issues remaining for future work will be discussed, including views about the use of spectroscopy to gain insights into newly discovered carbon materials, their structures and common defects.
5:15 PM - A4.3
Thermal Effects on the Raman Spectra of Diamond Nanoparticles.
Marc Chaigneau 1 , Hugues Girard 2 3 , Jean-Charles Arnault 2 , Razvigor Ossikovski 1
1 Laboratory of Physics of Interfaces and Thin Films, Ecole Polytechnique, Palaiseau France, 2 Diamond Sensors Laboratory, CEA LIST, Gif-sur-Yvette France, 3 Condensed Matter Physics Laboratory, Ecole Polytechnique, Palaiseau France
Show AbstractThe Raman spectra of diamond nanoparticles (NDs) exhibit a characteristic carbon-sp3 phonon peak that is broadened and down-shifted with respect to that of bulk diamond located at 1332 cm-1. We report on the temperature effects on the Raman spectra of NDs produced either by detonation synthesis or by milling of high-pressure high-temperature (HPHT) diamond. Moreover, different mean diameters (ranging from 3 nm to 50 nm) were investigated. In particular, we show that the behaviour of the carbon-sp3 peak is more consistent with the temperature increase of NDs due to the local heating caused by the laser (at 458 nm) rather than with the phonon confinement model alone widely used for nanoparticles spectra interpretation in the literature [1-3]. Local temperatures as high as 700 K are reached as confirmed by the anti-Stokes spectra. We use a Fano-resonance model, modified to account for the nanoparticle mean size and combined with the Klemens model for the temperature effect, to fit the experimental first-order Raman spectrum. We further show that the phonon behaviour with temperature also depends on the synthesis method (detonation or HPHT) and the NDs mean size. Furthermore, the thermal behaviour of the broad Raman band in the 1500-1700 cm-1 range is likewise dependent on the synthesis method used. Eventually, the reversibility of the thermally-induced phonon shift can be used to distinguish between the presence of sp2 clusters and that of surface hydroxyl groups in the nanoparticles.[1] M. Yoshikawa, Y. Mori, M. Maegawa, G. Katagiri, H. Ishida, A. Ishitani, Appl. Phys. Lett. 62, 3114 (1993).[2] J. W. Ager III, D. K. Veirs, G. M. Rosenblatt, Phys. Review B 43, 6491 (1991).[3] K. W. Sun, J. Y. Wang, T. Y. Ko, Appl. Phys. Lett. 92, 153115 (2008).
5:30 PM - A4.4
Local Stress-strain Structure at Dislocation in CVD Diamond Observed by Raman Peak-shift Mapping.
Yukako Kato 1 , Hitoshi Umezawa 1 , Hirotaka Yamaguchi 2 , Shinichi Shikata 1
1 Diamond Research Laboratory, Advanced Industrial Science and Technology (AIST), Tsukuba Japan, 2 Nanoelectronics Research Institute, Advanced Industrial Science and Technology (AIST), Tsukuba Japan
Show Abstract Diamond has attracted much attention due to the parameter for the high power device application. Because diamond has a wide band gap, high breakdown field, high thermal conductivity, it is expected to be a material using Schottky barrier diode [1, 2] as the high breakdown voltage and high temperature operation devices. For the development of that diamond device, the study on defects in respect to the device characteristics [3] is the most important topic for this consideration. However, the study covered this topic is not enough for the general discussion. In our presentation, it is shown that the raman microscopic peak-shift mapping as the experimental data of the local stress-strain at the dislocation in CVD diamond. The dislocation position is decided by the synchrotron x-ray topographies, Cross-Nicole images and Cathodoluminescence mapping. The sample is epitaxial diamond film. It was deposited on HPHT Ib(100) substrates by microwave plasma CVD method. Raman spectra and peak-shift map were recorded by using raman microscope, HR800 (Horiba Jobin-Yvon), with 633 nm excitation. From the peak-shift mapping around the dislocation, the stress-strain structure was observed. Cross-sectional peak-shift mapping at same area is shown the dislocation. Its grown direction is along <111>. Because of this observation, we suggest that this is the edge dislocation. From the luminescence mapping, it is shown that the observed dislocation and others are on one side of color zoning. This zoning is derived from the cubic or octahedral growth structure of CVD diamond.Acknowledgment:The New Energy and Industrial Technology Development Organization (NEDO) under the Ministry of Economy, Trade and Industry of Japan financially supported this study. The x-ray topography experiment was performed under approval of the Photon Factory Advisory Committee (Proposal No. 2010G168). We thank Dr. T. Teraji(NIMS) for the measurement of CL mapping and valuable discussions.Reference:[1] “Leakage current analysis of diamond Schottky barrier diode," H. Umezawa, T. Saito, N. Tokuda, M. Ogura, S. G. Ri, H. Yoshikawa, S. Shikata, Appl. Phys. Lett