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Selective Area Deposition of Hot Filament CVD Diamond on 100 mm MOCVD Grown AlGaN/GaN Wafers
摘要： A new technique is reported for selective growth of polycrystalline diamond by hot filament chemical vapor deposition (HFCVD) on AlGaN/GaN-on-Si (111) wafers without degradation of the underlying layers. Selective diamond seeding is accomplished by dispersing nano-diamond seeds in photoresist and patterned lithographically prior to HFCVD growth. A thin layer of plasma enhanced CVD SiNx, deposited prior to seeding and diamond deposition, was found to be essential to protect the AlGaN/GaN wafer. Methane concentration of 3.0% was used to achieve increased diamond growth rate and faster surface coverage. Excellent selectivity and minimal AlGaN surface damage were achieved due to the protective layer and faster surface coverage with increased methane concentration. Damage mitigation was confirmed by comparison of atomic force microscopy, x-ray diffraction, and Raman spectroscopy, each conducted before and after diamond deposition, and by SEM images of the final structures.
关键词： 2DEG,Reciprocal space mapping,III-Nitride,SiNx,Selective area deposition,CVD diamond,Photolithography,GaN decomposition
更新于2025-09-23 15:22:29
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Reactive wetting of binary Sn Cr alloy on polycrystalline chemical vapour deposited diamond at relatively low temperatures
摘要： Synthetic diamond has excellent mechanical, thermal, and electrical properties, which makes it an ideal material in a wide range applications from abrasive grinding tools to modern electronic devices. Hence, understanding the wettability of metals on the synthetic diamond is of great importance for the development of diamond-related materials and devices. In this study, the wettability and spreading kinetics of binary SneCr alloy on chemical vapour deposed (CVD) polycrystalline diamond compacts were investigated using a sessile drop method. In situ observation of contact angle at elevating temperatures indicated trace addition of Cr dramatically improved the wettability of Sn on CVD diamond, and the SneCr alloy started to wet CVD diamond at approximately 750 °C. Isothermal spreading kinetic analysis revealed that the spreading of SneCr alloy on CVD diamond was controlled by the kinetics of chemical reaction at advancing triple line. Microstructure characterization indicated that the formation of nano-sized scallop-like Cr7C3 grains was responsible for the improved wettability of SneCr alloy on CVD diamond substrate. The wetting temperature was found to play a determinant role in the interfacial carbide formation, and hence the reactive wetting of SneCr alloy on CVD diamond at temperatures from 700 to 900 °C.
关键词： Reactive wetting,Interface reaction,Chromium carbides,CVD diamond
更新于2025-09-19 17:15:36
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Diamond detector with laser-formed buried graphitic electrodes: micron-scale mapping of stress and charge collection efficiency
摘要： The paper reports the micron-scale investigation of an all-carbon detector based on synthetic single crystal CVD-diamond having an array of cylindrical graphitic buried-contacts, about 20 μm in diameter each, connected at the front side by superficial graphitic strips. To induce diamond-to-graphite transformation on both detector surface and bulk volume, direct-laser-writing technique was used. Laser-treatment parameters and cell shape have been chosen to minimize the overlapping of laser-induced stressed volumes. Optical microscopy with crossed polarizers highlighted the presence of an optical anisotropy of the treated material surrounding the embedded graphitized columns, and non-uniform stress in the buried zones being confirmed with a confocal Raman spectroscopy mapping. Dark current-voltage characterization highlights the presence of a field-assisted detrapping transport mainly related to highly-stresses regions surrounding buried columns, as well as superficial graphitized strips edges, where electric field strength is more intense, too. Notwithstanding the strain and electronic-active defects, the detector demonstrated a good charge collection produced by 3.0 and 4.5 MeV protons impinging the diamond, as well as those generated by MeV β-particles emitted by 90Sr source. Indeed, the mapping of charge collection efficiency with Ion Beam Induced Charge technique displayed that only a few micrometers thick radial region surrounding graphitic electrodes has a reduced efficiency, while most of the device volume preserves good detection properties with a charge collection efficiency around 90% at 60 V of biasing. Moreover, a charge collection efficiency of 96% was estimated under MeV electrons irradiation, indicating the good detection activity along the buried columns depth.
关键词： β-particles,3D detectors,graphitic pillars,IBIC,sc-CVD diamond,protons
更新于2025-09-11 14:15:04
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Research on the mechanism of micromachining of CVD diamond by femtosecond laser
摘要： Diamond is an excellent material in terms of hardness, thermal conductivity and chemical stability. In order to broaden its application area, the interaction mechanism of CVD diamond processed by femtosecond laser is analyzed based on laser micromachining technology. Through the threshold theory, the ablation threshold of CVD diamond is calculated. At the same time, the graphitization phase transition occurred in the diamond. The internal elements before and after the ablation of diamond by femtosecond laser are characterized by X-ray energy spectrum analysis. The changes of element content and bonding form are analyzed, and the relevant graphitization mechanism is revealed.
关键词： XPS,graphitization,ablation,CVD diamond,Femtosecond laser
更新于2025-09-11 14:15:04
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The Effect of Deposition Parameters on the Growth Rate of Microcrystalline Diamond Powders Synthesized by HFCVD Method
摘要： Conventional diamond powders (<10 μm) are generally produced from crushing large-sized diamonds synthesized by high-pressure and high-temperature (HPHT) technique, whereas they have many morphological imperfections. In the present work, these powders are served as diamond seeds and regrown by hot ?lament chemical vapor deposition (HFCVD). Deposition parameters—such as the carbon concentration, substrate temperature, and bias current—which play a determined role in the homoepitaxial growth rate of micron diamonds, are investigated in their respective usual ranges. As shown in the experimental results, under the preconditions of maintaining the good morphology of crystals and inhibiting polycrystal growth, the growth rate of isolated diamond crystals can be controlled at 0.9 μm/h. Besides, the ?nal improved powders have a wide range of particle sizes, which could fail to meet the requirements for commercial powders without the post-process of sieving.
关键词： CVD diamond powders,grain size distribution,homoepitaxial growth rate,deposition parameters
更新于2025-09-11 14:12:44
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Prospects of Impact Avalanche Transit-Time Diode Based on Chemical-Vapor-Deposited Diamond Substrate
摘要： We propose a chemical-vapor-deposited (CVD) diamond-based double-drift-region (DDR) impact avalanche transit-time diode (IMPATT) for use in microwave applications. CVD diamond is taken as the base substrate material. Simulations were carried out to perform direct-current (DC), small-signal, and noise analyses on the IMPATT. The results are in agreement with experimental reports. The IMPATT based on CVD diamond offers better performance compared with other materials reported to date at 26 GHz to 40 GHz. In the near future, this device could represent the best alternative for designers and semiconductor industry, due to its numerous advantages including higher DC-to-radiofrequency (RF) conversion efficiency (27.81%), highest power density (6.206 9 109 W m?2), minimum noise measure value (?98.22 dBm), and best optimized conductance–susceptance profile with lower quality factor (0.0215).
关键词： conversion efficiency,power density,impact ionization,DDR IMPATT,CVD diamond,noise measure
更新于2025-09-04 15:30:14
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CVD Diamond Interaction with Fe at Elevated Temperatures
摘要： Chemical vapor deposition (CVD) diamond is a prospective thin film material for cutting tools applications due to the extreme combination of hardness, chemical inertness, and thermal conductivity. However, the CVD diamond cutting ability of ferrous materials is strongly limited due to its extreme affinity to iron, cobalt, or nickel. The diamond–iron interaction and the diffusion behavior in this system are not well studied and are believed to be similar to the graphite–iron mechanism. In this article, we focus on the medium-temperature working range of 400–800 ?C of a CVD diamond–Fe system and show that for these temperatures etching of diamond by Fe is not as strong as is generally accepted. The starting point of the diamond graphitization in contact with iron was found around 400 ?C. Our results show that CVD diamond is applicable for the cutting of ferrous materials under medium-temperature conditions.
关键词： Fe–C interaction,CVD diamond,diffusion
更新于2025-09-04 15:30:14
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Ohmic graphite-metal contacts on oxygen-terminated lightly boron-doped CVD monocrystalline diamond
摘要： A process to obtain ohmic contacts on oxygen-terminated lightly boron-doped CVD monocrystalline diamond films was developed. Samples were contacted by Ti/Au metallic pads in the transmission line model (TLM) configuration. The electric contacts were placed onto a mesa structure produced on the CVD boron-doped layer. One of the samples was additionally implanted with helium ions at 10 keV in order to induce the formation of a graphitic layer underneath the diamond surface before contacting so as to improve electrical conduction. The electrical performance of both devices was characterized by the TLM method and compared. As a result, the sample with metallic electrodes exhibited a small and non-linear electrical conduction, while the graphitic/metallic contacts showed an ohmic behaviour with an estimated specific contact resistance as low as 3.3 × 10-4 Ω.cm2 for a doping level of a few 1017 cm-3. This approach opens the way to more efficient ohmic contacts on intrinsic or low-doped diamond that are crucial for the development of electronic devices and detectors.
关键词： oxygen terminations,graphitization,Ohmic graphite-metal contacts,lightly boron-doped CVD diamond film,ion implantation
更新于2025-09-04 15:30:14