New test beam results of 3D and pad detectors constructed with poly-crystalline CVD diamond
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Study of the triton-burnup process in different JET scenarios using neutron monitor based on CVD diamond
We present the results of analysis of triton burn-up process using the data from diamond detector. Neutron monitor based on CVD diamond was installed in JET torus hall close to the plasma center. We measure the part of 14 MeV neutrons in scenarios where plasma current varies in a range of 1-3 MA. In this experiment diamond neutron monitor was also able to detect strong gamma bursts produced by runaway electrons arising during the disruptions. We can conclude that CVD diamond detector will contribute to the study of fast particles confinement and help predict the disruption events in future tokamaks.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Performance study of polycrystalline CVD diamond detectors for fast neutron monitoring
Diamond detectors using polycrystalline CVD diamond substrates of thickness 300μm and 100μm were fabricated for fast neutron monitoring application.. The characterization of detectors was carried out using various tests such as leakage current, capacitance and alpha particle response. The performance of detectors was evaluated for fast neutrons at different neutron yields. The results presented in this work demonstrate that the diamond detectors will be suitable for monitoring fast neutrons.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Combined single-crystalline and polycrystalline CVD diamond substrates for diamond electronics
The fabrication of diamond substrates in which single-crystalline and polycrystalline CVD diamond form a single wafer, and the epitaxial growth of diamond films on such combined substrates containing polycrystalline and (100) single-crystalline CVD diamond regions are studied.
36 MATERIALS SCIENCE↗
Nitrogen and silicon defect incorporation during homoepitaxial CVD diamond growth on (111) surfaces
Chemical Vapor Deposited (CVD) diamond growth on (111)-diamond surfaces has received increased attention lately because of the use of N-V related centers in quantum computing as well as application of these defect centers in sensing nano-Tesla strength magnetic fields. We have carried out a detailed study of homoepitaxial diamond deposition on (111)-single crystal diamond (SCD) surfaces using a 1.2 kW microwave plasma CVD (MPCVD) system employing methane/hydrogen/nitrogen/oxygen gas phase chemistry. We have utilized Type Ib (111)-oriented single crystal diamonds as seed crystals in our study. The homoepitaxially grown diamond films were analyzed by Raman spectroscopy, Photoluminescence Spectroscopy (PL), X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The nitrogen concentration in the plasma was carefully varied between 0 and 1500 ppm while a ppm level of silicon impurity is present in the plasma from the quartz bell jar. The concentration of N-V defect centers with PL zero phonon lines (ZPL) at 575nm and 637nm and the Si-defect center with a ZPL at 737nm were experimentally detected from a variation in CVD growth conditions and were quantitatively studied. As a result, altering nitrogen and oxygen concentration in the plasma was observed to directly affect N-V and Si-defect incorporation into the (111)-oriented diamond lattice and these findings are presented.
36 MATERIALS SCIENCE↗
Tribological Characteristics and Applications of Superhard Coatings: CVD Diamond, DLC, and c-BN
Results of fundamental research on the tribological properties of chemical-vapor-deposited (CVD) diamond, diamondlike carbon, and cubic boron nitride films in sliding contact with CVD diamond in ultrahigh vacuum, dry nitrogen, humid air, and water are discussed. Furthermore, the actual and potential applications of the three different superhard coatings in the field of tribology technology, particularly for wear parts and tools, are reviewed.
Miyoshi, Kazuhisa↗
Selection of CVD Diamond Crystals for X-ray Monochromator Applications Using X-ray Diffraction Imaging
A set of 20 single crystal diamond plates synthesized using chemical vapor deposition (CVD) was studied using X-ray diffraction imaging to determine their applicability as side-bounce (single-reflection) Laue monochromators for synchrotron radiation. The crystal plates were of optical grade (as provided by the supplier) with (001) nominal surface orientation. High dislocation density was found for all samples. Distortions in the crystal lattice were quantified for low-index Laue reflections of interests using rocking curve topography. Maps of effective radius of curvature in the scattering plane were calculated using spline interpolation of the rocking curve peak position across the studied plates. For several selected plates, nearly flat regions with large effective radius of curvature were found (R 0 ≳ 30 - 70 m, some regions as large as 1 × 4 mm 2 ). The average width of the rocking curve for these regions was found to be about 150 μ rad (r.m.s.). These observations suggest that the selected CVD diamond plates could be used as intermediate-bandwidth monochromators refocusing the radiation source to a specific location downstream with close to 1:1 distance ratio.
36 MATERIALS SCIENCE↗
Growth Mechanisms of CVD Diamond Films Determined by a Novel TEM Technique
A novel transmission electron microscopy (TEM) technique is introduced for studying thick as-grown CVD diamond films. For a <001> texture consisting of 2-3 μm-diam grains with (001) and {111} facets, we have found that the core volume bounded by the (001) top facet and orthogonal {110} (i.e., the volume shadowed by the (001) top) is free from microtwins and stacking faults, but may contain a few dislocations. The remaining volume around the core, bounded by {111} facets, is filled with microtwins. The formation of microtwins in CVD diamond is associated with growth on {111}. For a <001> texture with only (001) and near {110} facets, the film is free from microtwins but contains more dislocations. A (001) twin-free column model is described to summarize all these observations.
36 MATERIALS SCIENCE↗
CVD Diamond, DLC, and c-BN Coatings for Solid Film Lubrication
When the main criteria for judging coating performance were coefficient of friction and wear rate, which had to be less than 0.1 and 10(exp -6) mm(exp 3)/N-m, respectively, carbon- and nitrogen-ion-implanted, fine-grain CVD diamond and DLC ion beam deposited on fine-grain CVD diamond met the requirements regardless of environment (vacuum, nitrogen, and air).
Miyoshi, Kazuhisa↗
CVD Diamond, DLC, and c-BN Coatings for Solid Film Lubrication
The main criteria for judging coating performance were coefficient of friction and wear rate, which had to be less than 0.1 and 10(exp -6) cubic MM /(N*m), respectively. Carbon- and nitrogen-ion-implanted, fine-grain, chemical-vapor-deposited (CVD) diamond and diamondlike carbon (DLC) ion beam deposited on fine-grain CVD diamond met the criteria regardless of environment (vacuum, nitrogen, and air).
Miyoshi, Kazuhisa↗
Effect of CO{sub 2}-laser power density on the absorption coefficient of polycrystalline CVD diamonds
The effect of 1-s irradiation of an uncooled polycrystalline CVD diamond plate by a focused cw CO{sub 2} laser beam with a power density of 300 – 800 kW cm{sup −2} is investigated. The absorption coefficient of the sample at a power density of 800 kW cm{sup −2} is found to be 0.035 cm{sup −1} larger as compared with that at 300 kW cm{sup −2}, which is related to the temperature dependence of its phonon-induced absorption with a change in temperature from 44 to 100 °C. It is shown that polycrystalline diamond, in contrast to other optical materials, does not exhibit nonlinear (avalanche-like) rise in absorption at high CO{sub 2}-laser power densities, at least up to 800 kW cm{sup −2}. (paper)
36 MATERIALS SCIENCE↗
Chemical Vapor-Deposited (CVD) Diamond Films for Electronic Applications
Diamond films have a variety of useful applications as electron emitters in devices such as magnetrons, electron multipliers, displays, and sensors. Secondary electron emission is the effect in which electrons are emitted from the near surface of a material because of energetic incident electrons. The total secondary yield coefficient, which is the ratio of the number of secondary electrons to the number of incident electrons, generally ranges from 2 to 4 for most materials used in such applications. It was discovered recently at the NASA Lewis Research Center that chemical vapor-deposited (CVD) diamond films have very high secondary electron yields, particularly when they are coated with thin layers of CsI. For CsI-coated diamond films, the total secondary yield coefficient can exceed 60. In addition, diamond films exhibit field emission at fields orders of magnitude lower than for existing state-of-the-art emitters. Present state-of-the-art microfabricated field emitters generally require applied fields above 5x10^7 V/cm. Research on field emission from CVD diamond and high-pressure, high-temperature diamond has shown that field emission can be obtained at fields as low as 2x10^4 V/cm. It has also been shown that thin layers of metals, such as gold, and of alkali halides, such as CsI, can significantly increase field emission and stability. Emitters with nanometer-scale lithography will be able to obtain high-current densities with voltages on the order of only 10 to 15 V.
Source record↗
Creation of Localized NV Center Ensembles in CVD Diamond by Electron Beam Irradiation
Creation of localized NV center ensembles, produced by irradiation of CVD diamond with nitrogen doped delta-layer with 200 keV electron beam and the subsequent annealing is demonstrated. Results of optical measurements of activated areas at different irradiation doses are presented. Issues concerning defect formation in diamond lattice during the electron beam impact are discussed.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Ohmic Contacts to CVD Diamond with Boron-Doped Delta Layers
Various methods for the formation of ohmic contacts to boron-doped δ layers in CVD-diamond epitaxial structures are investigated. In the first variant, an additional thin heavily doped layer was formed on the diamond surface to which an ohmic contact is formed. Then, the surface p{sup +} layer between the contact pads is etched out; therefore, the current in the structure flows only through a buried δ layer. In the second approach, the doped diamond selectively grows in the contact windows under a metallic mask after preliminary etching of the undoped diamond layer (cap) up to the δ layer. In this case, the heavily doped p{sup +} layer forms an end contact to the δ layer. These two variants differ in terms of the conditions of applicability, the complexity of the manufacturing technology, the value of the contact resistance, and can be used to solve problems in which it is necessary to have a different quality of the contacts, such as the formation of transistor structures or test cells for measuring physical characteristics.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Beam test results of 3D pixel detectors constructed with poly-crystalline CVD diamond
As a possible candidate for extremely radiation tolerant tracking devices we present a novel detector design - namely 3D detectors - based on poly-crystalline CVD diamond sensors with a pixel readout. The fabrication of recent 3D detectors as well their results in recent beam tests are presented. We measured the hit efficiency and signal response of two 3D diamond detectors with 50 × 50 μm cell sizes using pixel readout chip technologies currently used at CMS and ATLAS. In all runs, both devices attained efficiencies >98 % in a normal incident test beam of minimum ionising particles. The highest efficiency observed during the beam tests was 99.2 %.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Effects of Surface Treatments on Secondary Electron Emission from CVD Diamond Films
Secondary electron emission (SEE) properties of polycrystalline diamond films grown by chemical vapor deposition (CVD) were measured. The total secondary yield (sigma) from as-grown samples was observed to be as high as 20 at room temperature and 48 while heating at 700 K in vacuum. Electron-beam-activated, alkali-terminated diamond films have shown stable values of sigma as high as 60 when coated with CsI and similarly high values when coated with other alkali halides. Diamond coated with BaF2 had a stable sigma of 6, but no enhancement of the SEE properties was observed with coatings of Ti or Au. Hydrogen was identified to give rise to this effect in as-grown films. However, electron beam exposure led to a reduction in sigma values as low as 2. Exposure to a molecular hydrogen environment restored sigma to its original value after degradation, and enabled stable secondary emission during electron beam exposure. Atomic hydrogen and hydrogen plasma treatments were performed on diamond/Mo samples in an attempt to increase the near-surface hydrogen concentration which might lead to increased stability in the secondary emission. Raman scattering analysis, scanning electron microscopy, and Auger electron spectroscopy (AES) confirmed that hydrogen plasma and atomic hydrogen treatments improved the quality of the CVD diamond significantly. Elastic recoil detection (ERD) showed that heating as-grown diamond targets to 7OO K, which was correlated with an increase in sigma, removed contaminants from the surface but did not drive hydrogen from the diamond bulk. ERD showed that the hydrogen plasma treatment produced an increase in the hydrogen concentration in the near-surface region which did not decrease while heating in vacuum at 700 K, but no improvement in the SEE properties was observed.
Mearini, G. T.↗
A novel Mo-W interlayer approach for CVD diamond deposition on steel
Steel is the most widely used material in engineering for its cost/performance ratio and coatings are routinely applied on its surface to further improve its properties. Diamond coated steel parts are an option for many demanding industrial applications through prolonging the lifetime of steel parts, enhancement of tool performance as well as the reduction of wear rates. Direct deposition of diamond on steel using conventional chemical vapour deposition (CVD) processes is known to give poor results due to the preferential formation of amorphous carbon on iron, nickel and other elements as well as stresses induced from the significant difference in the thermal expansion coefficients of those materials. This article reports a novel approach of deposition of nanocrystalline diamond coatings on high-speed steel (M42) substrates using a multi-structured molybdenum (Mo) – tungsten (W) interlayer to form steel/Mo/Mo-W/W/diamond sandwich structures which overcome the adhesion problem related to direct magnetron sputtering deposition of pure tungsten. Surface, interface and tribology properties were evaluated to understand the role of such an interlayer structure. The multi-structured Mo-W interlayer has been proven to improve the adhesion between diamond films and steel substrates by acting as an effective diffusion barrier during the CVD diamond deposition.
36 MATERIALS SCIENCE↗
A Bayesian method to estimate the neutron response matrix of a single crystal CVD diamond detector
Detectors made from artificial chemical vapor deposition (CVD) single crystal diamond are very promising candidates for applications where high resolution neutron spectrometry in very high neutron fluxes is required, for example in fusion research. We propose a Bayesian method to estimate the neutron response function of the detector for a continuous range of neutron energies (in our case, 10 MeV ≤ E{sub n} ≤ 16 MeV) based on a few measurements with quasi-monoenergetic neutrons. This method is needed because a complete set of measurements is not available and the alternative approach of using responses based on Monte Carlo calculations is not feasible. Our approach uses Bayesian signal-background separation techniques and radial basis function interpolation methods. We present the analysis of data measured at the PTB accelerator facility PIAF. The method is quite general and it can be applied to other particle detectors with similar characteristics.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗