Philippe Bergonzo, The French Atomic Energy Commission (CEA), LIST Institute
Paul W May, University of Bristol
David A. J. Moran, The University of Glasgow
Robert J Nemanich, Arizona State University
Symposium Support Applied Diamond, Inc.
Cividec Instrumentation GmbH
Fine Abrasives Taiwan Co., LTD
Fraunhofer USA Inc., Center for Coatings and Diamond Technologies
Microwave Enterprises LTD.
Plassys - Bestek
DD3: Sensors I
Monday PM, November 30, 2015
Hynes, Level 1, Room 109
2:45 AM - DD3.01
Integrated Electrochemical and Optical Sensing Device Based on Fused Silica Fiber with B-NCD Thin Film Overlay
Robert Bogdanowicz 1 Mateusz Ficek 1 Michal Sobaszek 1 Marcin Gnyba 1 Mateusz Smietana 3 Jacek Ryl 4 Katarzyna Siuzdak 2
1Gdansk University of Technology Gdansk Poland2The Szewalski Institute of Fluid-Flow Machinery, Polish Academy of Sciences Gdansk Poland3Warsaw University of Technology Warsaw Poland4Gdansk University of Technology Gdansk PolandShow Abstract
The paper presents nanocrystalline boron-doped diamond (B-NCD) film as a coating for optical fibres. Seeding and growth processes of thin diamond films on fused silica optical fibres have been investigated. B-NCD films were deposited using Microwave Plasma Assisted Chemical Vapour Deposition (MW PA CVD). Optical fibre pre-treatment by dip coating in detonation nanodiamond (DND) seeding media has been performed. For the coating purpose, the DND suspension in polyvinyl alcohol (PVA) was chosen. The grain size distribution of nanodiamond particles in seeding medium was kept at approx. 10-50 nm. The B-NCD surfaces were analysed using high-resolution scanning electron microscopy (HR-SEM). The molecular structure of diamond has been examined with micro-Raman Spectroscopy. The sp3/sp2 ratio was calculated using Raman spectra deconvolution method. Thickness, roughness and optical properties of the nanocrystalline diamond films in VIS-NIR wavelength range were investigated on reference samples using spectroscopic ellipsometry. The B-NCD films deposited on glass reference samples exhibit high refractive index (n=2.3 at lambda;=550 nm) and low extinction coefficient. Furthermore, cyclic voltammograms (CV) were recorded to determine the electrochemical window and reaction reversibility at the B-NCD fiber-based electrode. CV measurements in aqueous media consisting of 5 mM K3[Fe(CN)6] in 0.5 M Na2SO4 demonstrated a width of the electrochemical window up to 1.03 V and relatively fast kinetics expressed by a redox peak splitting below 500 mV. Moreover, thanks to high-n B-NCD overlay, the coated fibers can be also used for enhancing sensitivity of long-period gratings (LPGs) induced in the fiber. The LPG is capable for measuring variations in refractive index of surrounding liquid by tracing shift in resonance appearing in transmitted spectrum. Possible combined CV and LPG-based measurements are discussed in this work. Due to extraordinary properties of diamond, which include high chemical and mechanical resistance, such films are highly desired for optical sensing purposes.
3:00 AM - DD3.02
Metal Nanoparticles/BDD Hybrid Electrodes for Analytic Detection of Pollutants in Water
Dounia Kamouni Belghiti 1 Emmanuel Scorsone 1 Jacques De Sanoit 1 Francesca Dini 2 Roberto Paolesse 2 Eugenio Martinelli 2 Corrado Di Natale 2 Philippe Bergonzo 1
1CEA, LIST, Diamond Sensors Laboratory Gif-sur-Yvette France2University lsquo;Tor Vergatarsquo; Rome ItalyShow Abstract
Diamond is well known as an innovative solution in terms of low cost, miniaturization and sensitivity for electrochemical sensing. Moreover, boron doped diamond (BDD) excellent properties that include a wide potential window in aqueous media, high corrosion resistance, chemical inertness, biocompatibility and low background current, make diamond one of the most promising material for electrochemical sensing in real unprocessed samples. In order to increase the selectivity of these sensors, several studies have demonstrated the interest of the presence metallic nanoparticles such as Pt or Ir on BDD electrodes, to promote electro-catalytic activity and enhance the electrochemical performance. This leads to the possibility to detect new species and namely derived products from enzymatic reactions such as acetylcholine oxidation. Here we have used this approach on a multiplexed system of several electrochemical sensors in order to fabricate an electronic tongue based on multiple metallic groups on BDD electrodes. From this approach, the simultaneous detection of analytes in a complex medium by an array of BDD electrodes covered with different kinds of metallic nanoparticles provides a unique finger print signature for each analyte, increasing the specificity and the selectivity of the sensor.
In this communication we will describe the process enabling the deposition of metallic nanoparticles: the approach used two steps: first, a thin film of a few nanometres was deposited using physical vapour deposition, and then this layer was submitted to an hydrogen plasma treatment, to de-wet the metallic layer while the diamond surface remains hydrogenated. Conditions were optimized to obtain nanoparticles with a subsequent narrow size distribution (20 +/- 3 nm) and an homogeneous particle density. Nanoparticles deposited by this method exhibit a very good stability in term of electro-activity and adhesion on BDD, even after several hundreds of current pulses up to 50mA.s-1. Here we present the use of this innovative electronic tongue for specific detection of several chemicals i.e. Paraoxon and imidacloprid, known toxic water pollutants for humans.
3:15 AM - DD3.03
3D Porous Diamond as a New Material for Electrochemical Interfacing with Neural Networks
Clement Hebert 1 Emmanuel Scorsone 1 Philippe Bergonzo 1
1CEA LIST Saclay Gif Sur Yvette FranceShow Abstract
Boron Doped Nanocrystalline Diamond (B-NCD) is known as a remarkable material for the fabrication of neural interfaces, taking advantage in particular of its good biocompatibility, electrochemical properties, and stability. Over the last years, in collaboration with electrophysiologists and biologists, such material was structured in various ways to design diamond devices, including MicroElectrode Arrays (MEAs) enabling to probe the neuronal activity distributed over large populations of either neurons or embryonic organs. Such developments were conducted within the frame of the Neurocare FP7 EU funded project, gathering technologists, electrophysiologists, biologists, and neurophysiologists. Specific MEAs were built such as neural prostheses or implants in order to compensate function losses due to lesions or degeneration of part of neural tissues like the retina.
However, despite remarkable properties in vivo and stimulating and recording properties very close to that of platinum, diamond exhibits a rather low double layer capacitance and a high interfacial impedance thus precluding its use for the fabrication of novel microelectrodes that go beyond the state of the art achievable with other materials (SIROF, Black Pt, Pedot etc).
This motivated the development of novel forms of diamond coatings based on highly porous and conductive carbonated materials to obtain highly porous diamond electrodes. The approach relies on the ability to grow diamond at low temperatures on 3D shape porous materials using electrostatic grafting of nanodiamonds as a seeding layer. The approach led to the fabrication a new material where a thick porous polypyrrole layer is uniformly coated with diamond. This material, now named SPDiaTM, exhibits a capacitance value increased up to a factor 800 with respect to planar diamond, as well as very low electrochemical interfacial impedances.
MEAs fabricated using SPDiaTM exhbit electrochemical performances matching those of the most advanced materials such as PEDOT-CNT, Iridium Oxide or porous Platinum, and further exhibit the remarkable biocompatibility of diamond.
Although not directly conducted within the NEUROCARE project, the authors would like to strongly acknowledge the EU Commission for its support under the GA FP7-NMP-280433, as well as all partners of the project from whom this work would not have been made feasible, with special thanks to L. Rousseau and G. Lissorgues from the ESIEE group and S. Picaud from the Vision Institute in Paris.
DD4: Material Characterization
Monday PM, November 30, 2015
Hynes, Level 1, Room 109
4:00 AM - *DD4.01
3D Imaging of Dopants in Chemical Vapour Deposition Diamond Films Using Atom Probe Tomography
Tomas Martin 1 Paul William May 2 Paul A.J. Bagot 1 Ken Haenen 3 Michael P. Moody 1
1University of Oxford Oxford United Kingdom2University of Bristol Bristol United Kingdom3University of Hasselt Hasselt BelgiumShow Abstract
Synthetic diamond is a material with vast potential in a variety of fields, ranging from a bio-compatible substrate for biological devices to high-power electronics and solar-power devices. Diamond is routinely grown by chemical vapour deposition (CVD), and p-type semiconductivity can be easily achieved using diborane (Bshy;2H6) in the precursor gases of this process. However, despite several candidate dopants, true n-type semiconductivity has never been successfully achieved, and atomic-scale characterisation is essential to this goal.
Atom Probe Tomography (APT) is a perfect tool to characterise the distribution of dopants within diamond films. APT is based upon the controlled evaporation of individual ions from a very sharp needle-shaped specimen, projecting them onto a position-sensitive time-of flight detector. From the resulting data, a three-dimensional atomistic reconstruction of the tip, incorporating millions of these ions, is computer generated with highly accurate spatial resolution and elemental composition. Recent instrument advances and in particular the advent of the laser-assisted local electrode atom probe (LEAP) has opened the technique up to the study of semiconductors and even insulating materials. Previous investigations of diamond-based materials using atom probe tomography are extremely limited, but a recent successful study utilising it to date meteoritic nanodiamond  highlights its potential. However, as yet there have been no investigations into synthetic or doped diamond using the latest generation of laser-assisted atom probes.
This talk will discuss the use of APT to map the behaviour and location of dopant atoms in CVD diamond films. One key advantage of the CVD approach is that diamond films can be grown directly onto commercially available presharpened silicon microtips. This eliminates the need for the Focused Ion Beam (FIB) liftout procedure usually used to prepare atom probe needles, which is unsuitable for diamond due to its uneven milling behaviour and evaporation mismatch with weld materials. We have successfully used this approach to demonstrate that boron is homogenous within the grain of residually boron-doped nanocrystalline diamond films. This talk will go on to look in more detail at the preparation methods and analysis parameters optimal for imaging diamond using APT, the effect of different grain sizes and doping levels of boron-doped films, as well as looking at the various candidates for n-type doping of diamond - primarily phosphorus, lithium, and nitrogen.
B Lewis et al, Meteoritic nanodiamond analysis by atom-probe tomography, 43rd Lunar and Planetary Science Conference (2012)
4:30 AM - DD4.02
Investigation of Dislocations in CVD Diamond
Alexandre Tallaire 1 Thierry Ouisse 3 Hakima Bensalah 2 Julien Barjon 2 Marc Legros 4 Vianney Mille 1 Ovidiu Brinza 1 Jocelyn Achard 1
1LSPM-CNRS Villetaneuse France2GEMaC Versailles France3LMGP Grenoble France4CEMES Toulouse FranceShow Abstract
In the past decade, tremendous improvements in the crystalline quality and purity of Chemically Vapour Deposited (CVD) diamond films have been achieved. Millimetre-thick CVD plates with an area close to 1 cmsup2; have now been made commercially available by several suppliers, opening the way to new applications in optics and electronics thanks to the outstanding properties of single crystal diamond. Nevertheless reducing extended defects in synthetic diamond still remains an important challenge. For example, dislocations affect current leakage in power devices, generate background fluorescence, or induce strain and unwanted birefringence of optical components. To achieve an optimal performance new strategies and technologies aiming at reducing dislocation densities are highly required.
In that context, analysing and identifying the nature and origin of dislocations in diamond can rely on a combination of several techniques. Dislocations can be revealed and counted using selective etching with H2/O2 plasma. By measuring the strain field surrounding a dislocation with Birefringence Microscopy (BM), important information can be obtained on the Burgers vector of the dislocation. Cathodoluminescence (CL) can also image the propagation direction of dislocations since they behave as efficient recombination centres for excitons. Finally, Transmission Electron Microscopy (TEM) allows a full identification of the type and Burgers vector of a dislocation. However, it requires heavy equipment and the preparation of a thin lamella of material.
In this work, dislocations produced in a thick CVD diamond crystal are analysed using a combination of plasma etching, BM, CL and TEM. It was found that dislocations are mostly of the mixed 45° or pure edge type. Each one leads to a recognisable etch-pit pattern. The advantages of each technique are discussed in order to get a better understanding of the formation of these defects in the synthetic material towards developing higher performance devices.
4:45 AM - DD4.03
Thermal Conductivity of Boron Doped Single HPHT Diamonds between 20 and 400 K
Dmitry Prikhodko 1 2 Sergey Tarelkin 2 3 Anton Golovanov 2 1 Vitaly Bormashov 2 Sergey Buga 2 1 Dmitry Teteruk 2 Mikhail Kuznetsov 2
1Moscow Institute of Physics and Technology (State University) Dolgoprudny Russian Federation2TISNCM Moscow, Troitsk Russian Federation3National University of Science and Technology MISiS Moscow Russian FederationShow Abstract
Bulk boron doped single crystal diamonds can be used as electric and thermal conductive substrates for wide variety of electronic devices. Detailed experimental data on electrical and thermal properties is required to model and design diamond based devices. Electrical transport properties of such crystals were reported in .
In this work we studied thermal conductivity of pure IIa and boron-doped IIb single crystal diamonds grown by the temperature gradient method under high pressure and high temperature (HPHT). The boron content was <1016 and ~1019 cm-3. Thermal conductivity measurements were carried out using Quantum Design PPMS by steady-state method in temperature range from 400 to 20 K on specially cut thin samples.
The thermal conductivity data has the accuracy less than 6% in the range 20-400 K.
The data was interpreted and fitted using the Callaway model. We considered phonon-phonon scattering, boundary scattering, scattering on point defects (13C isotopes and substitutional boron atoms) and extended defects (dislocations, etc.).
At low temperatures the thermal conductivity of boron-doped IIb diamond was found to be 2-4 times less than the thermal conductivity of pure IIa diamond. On the other side at high temperatures (>300 K) the difference is less than 30%. The decrease of thermal conductivity for boron-doped IIb diamond at T > 140 K is caused mostly by extended defects. In the operational range of diamond electronic devices (>300 K) the decrease of thermal conductivity of boron-doped IIb diamond should be taken into account, but it is unlikely that it can have critical influence on their performance.
 V.S. Bormashov, et al., Electrical properties of the high quality boron-doped synthetic single-crystal diamonds grown by the temperature gradient method, Diam. Relat. Mater. 35 (2013) 19-23.
5:00 AM - DD4.04
Microscopic Electrical Conductivity of Nanodiamonds after Thermal and Plasma Treatments
Jan Cermak 1 Halyna Kozak 1 Stepan Stehlik 1 Alexander Kromka 1 Bohuslav Rezek 1
1Inst. of Physics ASCR VVI Prague Czech RepublicShow Abstract
Nanodiamond (ND) electronic and optical properties may be tuned by surface termination, which is important for their usage in nano-chemical, sensing or energy conversion devices. Atomic termination is commonly achieved by a plasma treatment in the specific gas atmosphere. Recent experiments indicate that thermal and plasma treatments have a more complex effect on NDs compared to bulk diamond [Petit et al., Phys Rev. B 84, 233407 (2011)]. This can be attributed to nanoscale dimensions and commonly present amorphous carbon shell of the NDs, be they of detonation or HPHT origin. The amorphous carbon phase significantly influences electronic properties of detonation NDs as recently observed by surface potential measurements (KPFM) in correlation with infrared spectroscopy (FTIR) [Kromka et al., Phys.Stat.Sol. (b) 2015, in press]. In order to better understand the influence of surface treatment and surface condition on NDs electronic properties we performed local electrical conductivity measurements on individual and aggregated NDs by atomic force microscopy (AFM).
The detonation and HPHT NDs are characterized in the as-received state (i.e. after wet chemical cleaning), after plasma treatment in hydrogen, and after thermal annealing in air. Gold layers sputtered on n-doped silicon are used as electrically conductive, non-oxidizing substrates. NDs are deposited by immersing the substrates in the appropriate ND aqueous solution for 5 s. The samples are let dry in air and prior measurement they are heated to 180°C for 30 min (hot plate) to evaporate adhered moisture. AFM is operated in the PeakForce conductivity regime (PF-TUNA) which probes the electric current (in the range of < 10 pA) flowing between the substrate (biased up to +4 V) and the AFM tip during controlled cantilever approach-retract movements at low frequency (1 kHz). The differences in NDs conductivities are well correlated with FTIR and KPFM data. The influence of plasma treatment time, air moisture, carbon shell, contact barrier as well as actual diamond surface termination on the electrical conductivity of NDs will be discussed with view to their potential uses in sensors or energy conversion devices.
5:15 AM - DD4.05
Piezoresistivity in Ultra-Thin Nanocrystalline Diamond Membranes
Sien Drijkoningen 1 Stoffel Janssens 1 2 3 Ken Haenen 1 2
1Hasselt University Diepenbeek Belgium2IMEC vzw Diepenbeek Belgium3National Institute for Materials Science (NIMS) Tsukuba JapanShow Abstract
With their outstanding properties and ability to withstand harsh conditions, nanocrystalline diamond (NCD) membranes are a promising candidate for future use as sensitive pressure detectors . The transparency of glass allows a straightforward fabrication procedure on this substrate material. Here we&’ll discuss the fabrication of ultra-thin NCD membranes on different types of glass and the study of their piezoresistive properties when bulged under varying differential pressure. To this end, the membranes are positioned in the middle of a Hall bar structure, enabling the continuous probing of their electrical properties.
It will be shown that the underlying substrate plays an important role in the final pressure sensitivity of the membrane on top. This is primarily due to the amount of stress created in the film during the diamond growth process, leading to wrinkle formation. Heavily boron doped NCD membranes show a straight dependence of the sensor sensitivity on the type of glass substrate, directly observable by the amount of wrinkles in the membrane itself. The difference in thermal expansion coefficient between the glass types and the NCD film is thought to be responsible for this difference in stress, leading to an increase in sensitivity of 5 3% for membranes on Corning Eagle 2000 glass compared to those on Schott AF45 glass.
Furthermore, piezoresistive effect measurements on undoped H-termined surface conducting NCD membranes are discussed . These measurements reveal additional information on the complex transport mechanisms in this granular material and encourage further research on the piezoresistive properties of diamond.
 S.D. Janssens, S. Drijkoningen, K. Haenen, Applied Physics Letters 104/7 (2014), 073107.
 S.D. Janssens, S. Drijkoningen, K. Haenen, Applied Physics Letters 105/11 (2014), 101601.
SDJ is a Postdoctoral Fellow of the Japan Society for the Promotion of Science (JSPS).
5:30 AM - DD4.06
Conception and Evaluation of Innovative X-Ray Diamond Smart-Windows
Colin Delfaure 1 Nicolas Tranchant 1 Jean-Paul Mazellier 2 Pascal Ponard 3 Philippe Bergonzo 1 Samuel Saada 1
1CEA-LIST Gif-sur-Yvette France2Thales Research amp; Technology Palaiseau France3Thales Electron Devices Thonon-les-Bains FranceShow Abstract
The growing interest for high resolution X-Ray imaging in medical and industrial applications leads to increasing developments in the field of micro-focus transmission X-Ray tubes. In order to improve next generation devices, the subsequent increase of the power density and predicted instability of the emission currents must be addressed. We report here of the realization of innovative diamond windows where an integrated diamond detector is embedded in order to measure in real time the dose emitted by the X-ray tube without disturbing its operation. This ultimately leads to the possible fine control of the current instabilities via feedback loop control.
To understand and predict the mechanical and thermal specifications of such smart-windows, we modelled the physical parameters of the system. First the mechanical behaviour has been studied in order to downsize accurately the window. Then, a thermal analytical model has been developed to predict the temperature distribution within diamond windows under operating conditions and to check the mechanical downsizing. Finally the detection performances were modelled using Monte-Carlo simulations in order to predict the operating specifications of the devices as a function of the generated photocurrents.
Experimentally, several set-ups have been designed and used to characterize prototype devices. First, diamond smart-windows of 1 cm2 and 100 µm thick were grown using a homemade MPECVD reactor. Large diamond grains improve the heat spreading in the target and a smooth surface is required for its deposition. Hence films with a controlled (100) texture have been synthesized. A combined laser interferometric and scattered intensity set-up has been developed to optimize the diamond microstructure. Synthetized diamond windows prototypes have further been brazed on metallic rings in order to perform fatigue tests for up to 104 cycles under vacuum differential pressures. Eventually, the detection performances of such diamond smart-windows have been qualified under X-Ray exposure. A homemade EBIC set-up has been used to simulate the environment of an X-Ray tube and test the device under nano-beam conditions. Finally the performances have been evaluated in a first low-energy X-Ray tube prototype equipped with CNTFET cold cathodes thus capable of producing strong emission currents. The results will be presented and discussed.
DD5: Poster Session
Monday PM, November 30, 2015
Hynes, Level 1, Hall B
9:00 AM - DD5.01
Size Decrease of Detonation Nanodiamonds by Air Annealing Investigated by AFM and DLS
Stepan Stehlik 1 Marian Varga 1 Martin Ledinsky 1 Alexander Kromka 1 Bohuslav Rezek 1
1Institute of Physics, ASCR Prague Czech RepublicShow Abstract
Nanodiamonds with typical size of 4-5 nm are routinely prepared by a detonation from oxygen-deficient explosives on industrial scale. Although they are called nanodiamonds their structure is much more complex. According to latest understanding, a typical 5 nm detonation nanodiamond (DND) particle consists of: 1) a diamond core formed by sp3 hybridized carbon, 2) transient sp3/sp2, or disordered sp3 layer around the diamond core, 3) a surface shell formed by fullerene-like domains or graphite-like fragments. The surface shell in particular accommodates various surface functional groups that saturate dangling bonds and are responsible for the colloidal and chemical properties of the DNDs which are now relatively well understood and exploited.
On the other hand, quantum phenomena in diamond generally are still poorly understood compared to other semiconductors like Si or Ge. This is mainly due to very small exciton radius in diamond (1.6 nm vs. 4.9 nm in Si, 24.3 nm in Ge) which implicate a nanodiamond should be very small, probably below 2 nm (T. Yuan, K. Larsson, J. Phys. Chem. C 2014, 118, 26061minus;26069) to experimentally observe quantum phenomena. Recent progress led to preparation of DNDs with mean size of 2.8 nm by means of nanostructured explosives (V. Pichot et al., Diam. Relat. Mater. 2015, 54, 59-63). Another option may be to exploit the narrow size distribution of DNDs and use air annealing to decrease the size of regular DNDs by oxidative etching.
Here we report on investigation of air annealing effect on the size of DNDs by means of atomic force microscopy (AFM) on a substrate and dynamic light scattering (DLS) in colloidal solutions. For the AFM analysis we used common Si substrates which were densely covered by DNDs by a seeding treatment. The seeded substrates were then annealed in air at temperatures from 500 to 520°C for 50 minutes. The annealing temperatures were chosen based on previous thermogravimetric analysis. The size distribution of such annealed DNDs on Si substrate was analyzed by AFM. We observed considerable shift from the initial mean size of ~4.5 nm of not annealed DNDs to the size below 2 nm for DNDs annealed at 520°C. We then applied similar air annealing treatments to the original, macroscopic DND powder and subsequently prepared the colloidal solutions using ultrasound and centrifugation treatments. The DLS analysis showed decrease of the annealed DNDs size down to ~3 nm. As the air-oxidized DNDs strongly attract water (S. Stehlik et al., Diam. Relat. Mater., submitted) and DLS measures hydrodynamic diameter, this value may be overestimated due to presence of hydration shell. Our results thus indicate that air annealing indeed may be used to decrease the size of DNDs near to the quantum confinement region.
9:00 AM - DD5.02
Enhancing the Safe and Efficient High Pressure Microwave Plasma Assisted CVD Operating Regime for SCD Synthesis Using Continuous Wave and Pulsed Microwave Excitation
Matthias Muehle 1 2 Jes Asmussen 2 Michael Becker 1 Thomas Schuelke 1
1Fraunhofer USA, Center for Coatings and Diamond Technologies East Lansing United States2Michigan State University East Lansing United StatesShow Abstract
Achieving single crystalline diamond (SCD) wafer sizes of 1” and above requires serious effort during the growth process. Diamond is not increasing its lateral dimensions during the growth process. Thus there are 3 main concepts to increase SCD dimensions towards industrial demands: (1) mosaic growth, (2) flipped side approach, and (3) flipped seed approach. The first two concepts have been realized and reported . The built-up of internal stress between the individual clones or on the flipped side makes these approaches not ideal. The flipped seed approach seems as the only option to succeed in making large size SCD wafers of high quality and without internal stress. The two major concerns with the flipped side approach are a significantly higher amount of SCD post processing and far more total growth needed. While we made good progress in mastering the first issue  the problem of significantly increasing the growth rate still has to be addressed.
The development of new growth reactors allowed enhancing the safe and efficient growth window resulting in deposition rates up to 75 um/hour. This reactor was limited in maximum pressure by the stability of the plasma. The pressure was limited at 300 Torr due to the use of a microwave power supply pulsed at 120 Hz . We equipped a microwave cavity plasma reactor (MCPR) of type B with a switchable power supply between continuous and pulsed excitation. In pulsed mode the pulsing frequency, duty cycle and Pmin and Pmax can be varied. This allows us an extensive study of the fundamental reactor behavior in order to identify the best operation conditions for high-pressure SCD growth.
We propose a series of different reactor performance curve experiments. First, we will expand the pressure range to 400 Torr using a continuous wave discharge. Stability of the discharge for pressures as high as 400 Torr has already been proven in previous SCD deposition experiments. Due to the high power densities at high pressures we will be using single crystalline diamond substrates instead of silicon wafers. The substrate temperature as function of the input power will be recorded and the growth window extended. Photography and optical emission spectroscopy we will be recorded for plasma characterization. Reactor operational maps with variations of the different parameters of a pulsed microwave discharge, such as pulsing frequency, duty cycle and the role of Pavg vs. Ppeak by varying Pmin and Pmax, are performed. A set of power supply parameters for most efficient growth is identified. SCD growth experiments are performed using the optimized reactor setup.
 Yamada et al., Diamond and Related Materials 20:4 (2011), 616-619
 Muehle et al., Diamond and Related Materials 42 (2014), 8-14
 Lu et al., Diamond and Related Materials 37 (2013), 17-28
9:00 AM - DD5.03
Selective Epitaxial Growth of Diamond on Si (100) Substrates by Microwave Plasma CVD
Kazuki Komiya 1 Ryuhei Kojima 1 Ryota Yamada 1 Yuki Saito 1 Hideo Isshiki 1
1Graduate School of Informatics and Engineering, The University of Electro-Communication Chofu JapanShow Abstract
Diamond is attracting much attention for application to semiconductor devices because of its high carrier mobility, high thermal conductivity and wide band gap. Considering the cost and mass productivity, a silicon substrate is a candidate for the device platform. If the diamond selective growth on Si substrate is possible, diamond power devices and the control system LSI can be integrated. We have been studying epitaxial growth of single crystal diamond on Si substrate for the next-generation intelligent power module. However it is difficult to grow single crystal diamond film on Si substrate due to the large lattice mismatch and difference of thermal expansion. In this work, we take an approach to combine highly-oriented diamond nucleation  and selective growth in order to avoid the difficulties of diamond hetero-epitaxy.
The diamond nucleation and growth were carried out in microwave-plasma using gas mixtures of hydrogen and methane (0.5% CH4/ H2) with a pressure of 30 torr. The nucleation process was performed on silicon (100) substrate. In order to obtain highly-oriented diamond nuclei, a small amount of monomethyll silane (MMS: CH3SiH3 ) was added in the initial stage of nucleation. The oriented diamond nuclei were selectively remained by lithography and the O2 plasma etching processes after the nucleation. The pattern was the circles with a diameter of 3 mu;m and the interval was 60 mu;m. Cylindrical resonance microwave-plasma CVD was used to achieve high growth rates of diamond. The reactor pressure was 135 torr with 3% CH4/H2. Diamond grown on Si was observed by scanning electron microscopy (SEM), and crystallinity of the grown diamond was evaluated by Raman scattering spectroscopy.
After the first growth, the size of nuclei was evaluated to be a few tens nano-meters by SEM. In the second growth, diamond selective growth on the patterned nuclei was achieved and no diamond nucleation by the second growth process was observed. SEM photographs show arranged diamond cubes highly-oriented to Si substrate. The diamond crystalline cube with about 80mu;m cube was obtained after 16 hours growth. Micro-Raman scattering spectroscopy shows 1333cm-1 fine peak with the linewidth of less than 4cm-1, which is comparable to the bulk value and indicates the good crystallinity of the selective epitaxial diamond.
 H. Isshiki et al, Jpn. Appl. Phys. 51 (2012) 090108.
9:00 AM - DD5.04
Large Area Liquid-Phase Deposition of Low-k Carbon Nitride Films with Extremely Low Energy Consumption
Hideo Kiyota 1 Masafumi Chiba 1 Mikka Nishitani-Gamo 2
1Tokai University Hiratsuka Japan2Toyo University Kawagoe JapanShow Abstract
Shrink of device features in ultralarge-scale integration (ULSI) results in increased signal delay, power consumption, and cross-talk interference between device interconnections. Therefore, low-k insulating materials with dielectric constant k lower than 2 are needed for multilevel interconnections. Carbon nitride (CNx) is a promising low-k insulating material required for the modern ULSI technology because of high resistivity, low dielectric constant, and chemical stability , as well as other carbon materials such as diamond and amorphous carbon. While the CNx film has been studied by using conventional vapor depositions, the electrochemical synthesis to deposit the CNx film in organic liquid has been developed as an alternative deposition technique. Previously we have reported that the dielectric constant k as low as 2.6 was obtained for the liquid-phase deposited CNx films where acrylonitrile (CH2CHCN) liquid was used as the electrolyte . In this work, we have attempted a large area synthesis of low-k CNx films with extremely low energy consumption during the deposition process. Liquid deposition of the CNx film was achieved by application of a DC bias voltage between two electrodes immersed in acrylonitrile. Si substrates were mounted on both positive and negative electrodes with parallel plate configuration. Previously, the CNx films were obtained by application of bias voltage higher than 1000 V when the electrodes were separated by 10 mm. To reduce the bias voltage, a gap between the electrodes is adjustable from 10 mm to 0.1 mm by placing polytetrafluoroethylene (PTFE ) spacer between them. Typical deposition parameters to obtain the continuous and uniform films are a bias voltage of 200 V, a current density of 0.5 mA/cm2, a liquid temperature of 323 K. Reducing the gap distance, continuous and uniform CNx films can be deposited over 5-inch diameter Si wafers under the bias voltage lower than 100 V. A power consumption required to deposit the CNx films can be reduced to 0.1 W/cm2, estimating to be 70 W for the 300 mm wafer, which is much lower than ever reported. These results show that the large area deposition of low-k CNx film can be achieved by our liquid deposition system with reasonable energy cost.
 M. Aono and S. Nitta: Diamond Relat. Mater. 11 (2002) 1219.
 M. Higashi, H. Kiyota, T. Kurosu, and M. Chiba: Jpn. J. Appl. Phys. 50 (2011) 061502.
9:00 AM - DD5.05
Electronic Structure and N-Type Doping in Diamond from First Principles
Piotr Spiewak 1 Kamil Czelej 1 Krzysztof Kurzydlowski 1
1Warsaw University of Technology Warsaw PolandShow Abstract
Although p-type diamond is routinely available using boron, n-type material via impurity doping during the growth of diamond has historically been limited in success. As a consequence, this has led to search for a suitable donor impurity which can be introduced into the diamond lattice and which has a donor level close enough to the conduction band minimum. The standard method for defect calculations is density functional theory (DFT) applied to supercell model. Unfortunately, almost all theoretical supercell calculations based on local density or gradient density approximations suffer from an important shortcoming of DFT, namely the failure to reproduce well the bandgap of semiconductors and insulators. The considerable underestimation of the bandgap leads to uncertainties in the calculated formation and activation energies of point defects and dopants, and their defect levels in the bandgap. To overcome this deficiency we will apply one of the higher level electronic structure methods based on hybrid functional - the revised Heyd-Scuseria-Ernzerhof range-separated hybrid functional , that have proven reliable for describing the electronic and structural properties of defects in semiconductors [2,3].
We present ab initio calculations on the structural and electronic properties of the crystaline diamond. In this work elemental dopants such as As and Sb are explored within hybrid functional approach. The problems of the low solubility of these dopants and the possible formation of highly stable V-As and V-Sb complexes  will be investigated in details. Also, the co-doping technique that combines properties of more than one defect which conspire to yield the desired electrical (or optical) properties will be investigated based on recently reported  possibilities in this topic.
 J. Heyd, G. E. Scuseria, and M. Ernzerhof, J. Chem. Phys. 118, 8207 (2003), and erratum ibid. 124, 219906 (2006).
 Advanced Calculations for Defects in Materials, edited by A. Alkauskas, P. Deak, J. Neugebauer, A. Pasquarello, and C. G. Van de Walle (Wiley-VCH, Weinheim, Germany, 2011).
 P. #346;piewak and K. J. Kurzyd#322;owski, Phys. Rev. B 88, 195204 (2013)
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 U. Schwingenschlögl, A. Chroneos, C. Schuster, and R. W. Grimes, J. Appl. Phys. 110, 056107 (2011).
9:00 AM - DD5.06
Fabrication of Diamond-Like Carbon Emitter Patterns by Room-Temperature Curing Nanoimprint Lithography with PDMS Molds Using Polysiloxane
Shuji Kiyohara 1 Shogo Yoshida 1 Ippei Ishikawa 1 Toru Harigai 2 Hirofumi Takikawa 2 Masahiko Watanabe 3 Yoshinari Sugiyama 3 Yukiko Omata 3 Yuichi Kurashima 4
1National Institute of Technology, Maizuru College Maizuru Japan2Toyohashi University of Technology Toyohashi Japan3ELIONIX INC. Hachioji Japan4AIST Tsukuba JapanShow Abstract
The diamond-like carbon (DLC) expected to have various applications. For example, it can be used emitter for flat panel display (FPD), micro gear for MEMS as electrical and mechanical applications respectively. Therefore, the nanopatterning technique for DLC films is essential to the fabrication of functional DLC based micro and nano devices.
The room-temperature curing nanoimprint lithography (RTC-NIL) using polysiloxane [HSG-R7-13, Hitachi Chemical Co., Ltd.] that we developed, which has certain advantages, including short steps, high throughput and low cost, and keeping molds from thermal expansion and contraction, compared with conventional thermal-cycle NIL. We have already investigated the micro patterning of DLC films in RTC-NIL, using glass-like carbon (GLC) molds, which have been fabricated with electron cyclotron resonance (ECR) O2 (oxygen) ion shower etching using polysiloxane in the electron beam (EB) lithography technology that we developed. However, we found that RTC-NIL process using GLC mold could not fabricate convex DLC emitter patterns because the fabricated GLC molds have the convex patterns. To overcome this problem, we proposed the use of polydimethylsiloxane (PDMS) molds which have reverse patterns of GLC molds. We investigated the fabrication of DLC emitter patterns by RTC-NIL using PDMS mold, as an application to the emitter for FPD.
The DLC (10 mm-square, 500 nm-thickness, 2 nm-arithmetic average roughness, ta-C: Tetrahedral amorphous carbon, Si substrate) which has excellent properties similar to diamond properties was used as a pattern material. A PDMS [KE-106, Shin-Etsu Chemical CO., Ltd.] was used as a mold material and fabricated by the following optimum conditions of 36 h-first curing time at room temperature and 15 min-second curing time at 150 #8451;. The polysiloxane is in the state of sticky liquid at room temperature and stable in air. Therefore, the polysiloxane was used EB resist and oxide mask material in EB lithography, and also used as RT-imprint material.
We fabricated the PDMS mold with concave dots. Each dot is 5 µm-diameter and 400 nm-depth. We carried out the RTC-NIL process using the PDMS mold under the following optimum imprint conditions of 0.5 MPa-imprinting pressure, 1.5 min-the time between spin-coat and imprint, and 5 min-imprinting time. The residual layer of polysiloxane film was removed with ECR CHF3 (trifluoromethane) ion shower under the conditions of 300 eV-ion energy and 3 min-etching time. We found that the maximum etching selectivity of polysiloxane film against DLC film was 6, which was obtained under 400 eV-ion energy. Then we processed the imprinted polysiloxane patterns on the DLC film with an ECR O2 ion shower at 12 min-etching time. As a result, we succeeded in fabricating convex DLC emitter patterns with high accuracy which has 5 µm-diameter and 500 nm-height.
9:00 AM - DD5.07
Electron Affinity of Cubic Boron Nitride Terminated with Vanadium Oxide
Yu Yang 1 Tianyin Sun 1 Joseph Shammas 1 Manpuneet Kaur 2 Mei Hao 1 Robert J. Nemanich 1
1Arizona State University Tempe United States2Arizona State University Tempe United StatesShow Abstract
Cubic boron nitride (c-BN) is isoelectronic to diamond, and H-terminated c-BN has been shown to exhibit a negative electron affinity (NEA) surface, which may enable applications in thermionic and photon-enhanced energy conversion devices. The ability to withstand high temperature operation is an important factor in the thermionic emission applications. Theoretical and experimental studies have indicated that transition metal oxides can significantly influence the electronic properties of diamond. In this study, the presence of a thermally stable NEA for a c-BN surface with vanadium-oxide-termination is achieved. The c-BN films were prepared by electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR-PECVD) employing BF3 and N2 as precursors. Thin vanadium layers of ~0.1 and 0.5 nm were deposited on the c-BN surface in an electron beam deposition system. Oxidation of the metal layer was achieved by an oxygen plasma treatment. The resultant surfaces were analyzed using in-situ ultraviolet and X-ray photoelectron spectroscopy (UPS/XPS). After 650 0C thermal annealing, the vanadium oxide on the c-BN surface was determined to be VO2, and the surfaces were found to be thermally stable, exhibiting an NEA. In comparison, the oxygen-terminated c-BN surface, where B2O3 was detected, showed a positive electron affinity (PEA) of ~1.2 eV. The B2O3 evidently acts as a negatively charged layer introducing a surface dipole directed into the c-BN. Through the interaction of VO2 with the B2O3 layer, a B-O-V layer structure would contribute a dipole between the O and V layers with the positive side facing vacuum. The lower enthalpy of formation for B2O3 is favorable for the formation of the B-O-V layer structure, which provides a thermally stable surface dipole and an NEA surface.
This work is supported through the Office of Naval Research under Grant # N00014-10-1-0540, and the National Science Foundation under Grant # DMR-1206935.
9:00 AM - DD5.08
Enhanced Field Electron Emission and Plasma Illumination Properties from Hexagonal Boron Nitride/Nanocrystalline Diamond Heterostructures
Sankaran K J 1 D. Q. Hoang 1 K. Srinivasu 5 Stuart Turner 2 Paulius Pobedinskas 1 Sien Drijkoningen 1 Jo Verbeeck 2 Jan D'Haen 1 3 K. C. Leou 5 I-Nan Lin 4 Ken Haenen 1 3
1Institute for Materials Research (IMO), Hasselt University Diepenbeek Belgium2Electron Microscopy for Materials Science (EMAT), University of Antwerp Antwerp Belgium3IMOMEC, IMEC vzw Diepenbeek Belgium4Department of Physics, Tamkang University Tamsui Taiwan5Department of Engineering and System Science, National Tsing Hua University Hsinchu TaiwanShow Abstract
Following the discovery of excellent field electron emission (FEE) from carbon nanotube arrays, much attention has been paid to field emission from nanostructures. Both the large field enhancement factor and the low cost show signs of a promising future for these nanoscale emitters in the application of display devices and vacuum electronics, etc. Diamond films possess many desirable physical and chemical properties and have been the focus of intensive research since the successful synthesis of diamonds in the low pressure and low temperature chemical vapor deposition (CVD) process. Due to the negative electron affinity (NEA) characteristics of the surface of diamond films, diamond is considered to have great potential for application as electron field emitter. Besides, it has been found that NEA also appears on cubic and hexagonal boron nitride (BN) surfaces. A significant NEA was detected on an hBN surface treated with hydrogen or oxygen plasma. Therefore, hBN is expected to be a promising material for a cold cathode. Being encouraged by the unique possibility to combine two nanostructured materials, we fabricated novel bilayers where an hBN film is grown on a nanocrystalline diamond (NCD) one.
The NCD film is first grown by microwave plasma CVD, and then the hBN film is synthesized on the NCD film using a home built radio-frequency sputtering system. Superior FEE properties of the given structures are observed. FEE properties of hBN-NCD heterostructures show a high emission current density of 0.46 mA/cm2 at an applied field of 61.3 V/mu;m, and a low turn-on field of 35.5 V/mu;m compared to the 0.15 mA/cm2 emission current density (at an applied field of 91.6 V/mu;m) and 46.6 V/mu;m turn-on field for bare hBN. This enhancement in the field emission for hBN-NCD heterostructures originates from the unique materials combination, resulting in good electron transport from NCD to hBN and efficient field emission of electrons from the hBN nanowalls. The potential application of this heterostructure is demonstrated by the plasma illumination measurements where the lowering of the threshold voltage to 410 V confirms the role of hBN-NCD heterostructures in the enhancement of electron emission.
K. J. Sankaran is a Pegasus Postdoctoral Fellow of the Research Foundation - Flanders (FWO Vlaanderen).
9:00 AM - DD5.09
Fabrication of Diamond-Like Carbon Microgears in Room-Temperature Curing Nanoimprint Lithography Using Ladder-Type Hydrogen Silsesquioxane
Shuji Kiyohara 1 Yuto Shimizu 1 Ippei Ishikawa 1 Toru Harigai 2 Hirofumi Takikawa 2 Masahiko Watanabe 3 Yoshinari Sugiyama 3 Yukiko Omata 3 Yuichi Kurashima 4
1National Institute of Technology, Maizuru College Maizuru Japan2Toyohashi University of Technology Toyohashi Japan3ELIONIX INC. Hachioji Japan4AIST Tsukuba JapanShow Abstract
The diamond-like carbon(DLC)has been conventionally used to coat such things as the surface of cutting tools and artificial joints because it has exhibited unique properties such as high hardness, high wear resistance and corrosion resistance; and so it is expected to have various applications. For example, it can be used as DLC based microgears for medical MEMS. Therefore, the nanopatterning technique for a DLC is essential to the fabrication of functional micro/nano devices.
We have already investigated the nanopatterning of chemical vapor deposited (CVD) diamond films in room-temperature curing nanoimprint lithography (RTC-NIL), using glass-like carbon [GLC (10 mm-square, 3.2 mm-thickness, 1.6 nm-arithmetic average roughness), PXG-35, Hitachi Chemical Co., Ltd., Japan] mold, and then we fabricated the DLC [ta-C : tetrahedral amorphous carbon, 10 mm-square, 500 nm-thickness, 2 nm-arithmetic average roughness] film which has concave microgear patterns with high accuracy in RTC-NIL using polysiloxane. However, RTC-NIL process using GLC mold could not fabricate the DLC film with convex microgear patterns. To overcome this problem, we proposed the use of polydimethylsiloxane (PDMS) mold with concave microgear patterns and also the use of ladder-type hydrogen silsesquioxane (HSQ) as RT-imprinting material which we can expected to be pressed under low imprinting pressure, compared with cage-type HSQ. We investigated the fabrication of DLC based microgears in RTC-NIL using the HSQ, as an application for the medical MEMS.
The HSQ [OCNL 103 T-2 13000, TOKYO OHKA KOGYO Co., Ltd.] which is an inorganic polymer of sol-gel system turns into a gel when exposed to air and has the siloxane bond. Therefore, the HSQ was used as RT-imprinting material, and also used as an oxide mask material in electron cyclotron resonance (ECR) O2 ion shower etching. We fabricated the PDMS mold with concave microgear patterns which has 50 mu;m-tip diameter and 300 nm-depth. We carried out the RTC-NIL process using the PDMS mold under the following optimum conditions of 0.1 MPa-imprinting pressure and 1 min-imprinting time. We found that the maximum etching selectivity of the HSQ film against the DLC film was 5, which was obtained under 400 eV-ion energy. The residual layer was removed with ECR CHF3 ion shower under the following conditions of 300 eV-ion energy and 4 min-etching time, and then microgear patterns of the HSQ on the DLC film were processed with ECR O2 ion shower under the following conditions of 400 eV-ion energy and 12 min-etching time. The convex DLC based microgear patterns, which have 50 mu;m-tip diameter and 500 nm-height were fabricated with high accuracy.
9:00 AM - DD5.10
Thermal Conductivity Characterization of Foaming Porous Copper and Porous Diamond-Copper
Hongdi Zhang 1 Tongxiang Fan 1
1Shanghai Jiao Tong University Shanghai ChinaShow Abstract
Biporous copper was successfully fabricated through tape casting. C7H10N2O2S (0-1.5wt.%) was used as foaming agent for the one-step foaming method, while 18%-72wt% of C18H36O2 and 1.5wt% of C7H10N2O2S were used as foaming agent for the two-step foaming method. To optimize the preparation process, foaming agent content, sintering temperature and holding time were considered. Thermal conductivity characterization was evaluated by capillary performance and gas permeability. The results indicate that increasing the content of the foaming agent increases the pumping rate, while porosity and gas permeability fluctuate for the one-step method. In contrast, porosity, pumping rate and gas permeability increase with an increase in C18H36O2 content but with a decrease in sintering time for the two-step method. Fractal dimension was also used to estimate the biporous distribution and size. Porous copper was fabricated into a heat pipe under optimal conditions. The optimal planar heat pipe resistance was 0.1834 K/W, temperature differential was 8.9 0C, and equivalent thermal conductivity was 1457 W/mmiddot;0C. It is suggested that biporous copper prepared by tape casting may be an effective wick structure for heat pipes. Porous diamond-copper was achieved through the foaming method. Before combining the diamond, copper and foaming agent, the diamond was metalized with carbide forming elements. Thermal conductivity can be increased with the addition of high thermal conductive diamond.
9:00 AM - DD5.11
Charge Transport and Carrier Lifetime Properties of Single Crystal Diamond Irradiated with Swift-Heavy Ion Beams
Ayan Bhattacharya 1 Andreas Stolz 2 Timothy A. Grotjohn 1
1Michigan State University East Lansing United States2Michigan State University East Lansing United StatesShow Abstract
Diamond has outstanding mechanical, electrical and optical properties, which inherently makes it a radiation tolerant material at extreme radiation environment. Single crystal diamond has a large bandgap (~ 5.47 eV), large atomic displacement energy (~ 43eV) and high electric breakdown field ( 107 V cm-1). The application of diamond for high energy radiation detector has become an emerging field in the last few decades. Single crystal diamond plates grown at Michigan State University (MSU) by microwave assisted chemical vapor deposition (MPACVD) are used to develop detectors for swift heavy ion beams. Detection performance of the samples were studied by irradiating them with swift heavy ion beams in the range of 100-150 MeV/u at the National Superconducting Cyclotron Laboratory (NSCL) at MSU. In addition to the diamond plates grown at MSU, commercially available electronic grade plates were also fabricated into detectors and tested in the same radiation environment.
Post irradiation, the charge transport properties of the detectors were studied by the transient-current technique (TCT). A 232U α-particle source was used to collimate particles through an aperture of 1-mm diameter onto heavily and lightly irradiated segments of the diamond detectors. Current pulse shapes were studied in the range of 0.1 V/mu;m - 1.1 V/mu;m applied field. The current pulse shapes of both electron and holes of the irradiated detectors were also compared to the signals collected from a detector fabricated by a non-irradiated electronic grade diamond. Due to radiation induced damage, a significant drop of charge collection and carrier life time was observed in the heavily irradiated segment in comparison to the lightly irradiated segment.
9:00 AM - DD5.12
Modeling of Transition Metal Color Centers in Diamond
Nick Gothard 1 Douglas Dudis 2 Luke J Bissell 2
1University of Dayton Research Institute Dayton United States2Air Force Research Laboratory Dayton United StatesShow Abstract
Diamond stands out among single-photon sources due to an intrinsically large band gap, efficient electrical excitation, the ability to host bright optical centers, photo-stable emission, room-temperature operation, short excited state lifetimes, and the ability to host hundreds of different color centers. Currently, most of these centers are active in the optical spectrum, but a single-photon source in the IR would represent a significant advancement. In pursuit of this end, the effects of a number of different transition metal atoms upon the diamond lattice have been investigated via cluster calculations using the General Atomic Molecular and Electronic Structure System (GAMESS) code. The importance of cluster size and electron correlation effects is considered, and time-dependent DFT and multi-configurational SCF approaches are compared.
9:00 AM - DD5.14
2D and 3D Models of Diamond Growth Using Kinetic Monte Carlo Modelling
Paul William May 1 Neil L. Allan 1 Jeremy N Harvey 1 W Jeff Rodgers 1
1Bristol University, School of Chemistry Bristol United KingdomShow Abstract
A three-dimensional kinetic Monte Carlo model has been developed to simulate the chemical vapor deposition of a diamond (100) surface under conditions used to grow single-crystal diamond (SCD), microcrystalline diamond (MCD), nanocrystalline diamond (NCD), and ultrananocrystalline diamond (UNCD) films. The model includes adsorption of CHx (x = 0, 3) species, insertion of CHy (y = 0-2) into surface dimer bonds, etching/desorption of both transient adsorbed species and lattice sidewalls, lattice incorporation, and surface migration but not defect formation or renucleation processes. We find that SCD and MCD growths are dominated by migration and step-edge growth, whereas in NCD and UNCD growths, migration is less and species nucleate where they land. Etching of species from the lattice sidewalls has been modelled as a function of geometry and the number of bonded neighbors of each species. Choice of appropriate parameters for the relative decrease in etch rate as a function of number of neighbors allows flat-bottomed etch pits and/or sharp-pointed etch pits to be simulated, which resemble those seen when etching diamond in H2 or O2 atmospheres. Simulation of surface defects using unetchable, immobile species reproduces other observed growth phenomena, such as needles and hillocks.
9:00 AM - DD5.15
Further Progress in Diamond Microplasmas
Paul William May 1 Benjamin S Truscott 1 Neil A. Fox 1
1Bristol University, School of Chemistry Bristol United KingdomShow Abstract
Microplasmas are electrical discharges wherein one of the critical dimensions is <1 mm. Hollow-cathode microdischarges can achieve high densities with only moderate power input, and as their size decreases, their working pressure typically increases; indeed, for cavities with dimensions ~100 µm, operation has been demonstrated at atmospheric pressure. Arrays of microplasmas have a variety of potential applications, including removing contaminants from air supplies in enclosed environments (submarines; spacecraft), as flat panel light sources (especially of near monochromatic light), as large-area UV sources, and as small-scale flow reactors for chemical processing.
We recently presented the first results from an all-diamond microplasma device, in which the electrodes and the insulating dielectric were fabricated from boron-doped and undoped diamond, respectively, with the cavity formed by laser drilling a hole through all three layers. These devices operated at about 1 W d.c. power, and exhibited a sustaining voltage of 300-400 V for operation in up to 1 atm pressure helium.
We now present data from the second and third generation of these devices, with improved design and more comprehensive electrical diagnostics. The new devices are able to operate over a very wide range of currents and at up to 10 atm in He, striking reliably and functioning stably for many hours.
We find that the device Paschen curves (p×d vs V) closely resemble those for a Townsend discharge between parallel plate electrodes, despite the hollow cathode-type geometry. Current-voltage (I-V) characteristics are almost flat for all pressures and regardless of cavity dimensions, with sustaining voltages being typically 250-300 V over the range I = 4-15 mA, and only small differences arising with variations of pressure and discharge current.
In summary, we have now demonstrated, high pressure, high power density non-equilibrium glow discharges in monolithic diamond devices, with asymp; 30 min continuous operation at 9.5 atm being achieved for the smallest (asymp; 50 µm) cavities. Operation at lower pressure and discharge current extends the device lifetime to days, and potentially weeks. We have also demonstrated plasma formation in 2D slots (200 µm wide × 1 mm long) and small (2×2; 3×3) cavity arrays.
9:00 AM - DD5.16
Stability of Operation of Atmosphere-Exposed, Hydrogen-Terminated Diamond FETs under Constant Operation
David Andrew Macdonald 1 Alexandre Tallaire 2 Claudio Verona 3 Ernesto Limiti 3 David A.J. Moran 1
1University of Glasgow Glasgow United Kingdom2French National Centre for Scientific Research Paris France3University of Rome Tor Vergata Rome ItalyShow Abstract
Diamond is an interesting material for high power FET fabrication owing to its high breakdown field of >10MVcm-1 and high thermal conductivity of 22Wcm-1K-1. It is also suited for operation in extreme environments due to its robustness, chemical inertness and radiation resistance . For high power operation achieving a large output current at a large operation voltage is desirable. Any mechanisms therefore that result in reduced output current at maximum drain bias voltage would be detrimental to device performance.
Hydrogen terminated diamond FETs take advantage of surface transfer doping using atmospheric adsorbates as a charge transfer layer resulting in the formation of a 2DHG channel below the diamond surface. This has been shown to be unstable, with atmospheric adsorbates sublimating from the surface around 200 °C . Variations in the properties of the charge transfer layer can result in diminished carrier concentration reducing current transport through the device.
This work presents the DC response with time of both un-gated and gated (FET) structures on hydrogen terminated single crystal diamond under constant voltage biases. It is believed that this is the first study of this kind pertaining to the stability of diamond FETs. Degradation of current over extended periods of constant operation has been observed experimentally. The nature of the observed IV response of both un-gated and gated structures appears to be an inverse exponential decrease of up to 10% in 10 minutes of continuous operation. It is suggested that the method of current degradation is due to charging of the structures with positive charge as a result of charge trapping. As a similar response is achieved from both un-gated and gated structures it is also proposed this trapping happens at the interface between surface adsorbate and diamond surface. Extended operation can result in increased temperature of the structures, however diamond&’s high thermal conductivity could counter act this by dissipating heat effectively, although it appears this has not yet been verified experimentally.
This investigation will continue with varying gate and drain biases to determine the whether the reduction is determined by the magnitude of potential across the device. Devices of different widths will also be tested to determine if the absolute non-normalized current is a factor in total current reduction.
 - Wort, C. J, et al., (1999), Proceedings of SPIE 3705 p.119
 - Umewaza, H. et al., (2014), Diamond Metal-Semiconductor Field-Effect
Transistor with Breakdown Voltage over 1.5 kV, IEE device letters, 35, p1112
 - Blakemore, J. S., (1985), Second edition, Solid state Physics. Cambridge University Press,
 - Landstrass, M.I., Ravi, K. I. (1989), Hydrogen passivation of electrically active defects in diamond, Appl. Phys. Lett., 55, p1391
9:00 AM - DD5.17
Investigation into the Minimum Feature Size for Reactive-Ion Etched (RIE) Micro and Nano-Scale Polycrystalline Diamond Mechanical Resonators.
Andrew William McGlone 1 Oliver A. Williams 2 David A.J. Moran 1
1University of Glasgow Glasgow United Kingdom2Cardiff University Cardiff United KingdomShow Abstract
Owing to its unique mechanical properties such as high acoustic velocity (18,024 m/s)  and high thermal conductivity (2100 W/mK) , diamond is an attractive candidate for use in micro-electro-mechanical systems (MEMS) devices and is implemented in numerous ways including micro-switching and mass detection. Reported is a process developed to fabricate and characterise cantilever shaped resonant structures of varying mass and dimension.
Polycrystalline diamond samples with grain size sub-500 nm are produced by microwave plasma chemical vapour deposition on a silicon substrate in a 1% CH4/H2 environment. Samples are patterned using a Vistec VB6 UHR EWF electron beam lithography tool. Using an Al or HSQ mask, the patterned samples are etched in an RIE tool with an O2/Ar gas mixture returning an anisotropy of ~80#730;. The etched diamond structures are released from the silicon substrate by wet etching the sample in KOH. The mass of the structures are scaled down until mechanical failure is observed, demonstrated by degradation of frequency response and Q factor. The structures are actuated in air by mechanical force from either compressed air or a piezo clamp and resonant frequency and Q factor observed by means of a vibrometer. Experimental results are compared with simulations and sample specific values for Young&’s modulus are reported.
1Bolz R E “CRC Handbook of Tabl