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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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Controlling Silver Ion Release from Ag-Based Nanocoatings by Plasma Surface Engineering
摘要： Environmental surfaces have been widely recognized as an important source of hospital-associated transmissions. A number of silver-based antibacterial coatings have been reported in the literature. However, the success of any antibacterial strategy depends on the ability to control the kinetics of the silver ions released from the coating. The novel strategy proposed in this work is based on plasma surface engineering for a controlled-release of silver ions. Plasma-based nanocoatings, plasma oxidation processes and surface patterning of silver coatings were designed and optimized. Surface analyses such as XPS and AFM, as well as silver ion release over 168 h, was evaluated by MIP-AES. Results showed that surface plasma engineering successfully allow tuning the silver release and bioactivity in Ag-containing antibacterial coatings.
关键词： diamond-like carbon,plasma oxidation,silver release,antibacterial activity
更新于2025-09-23 15:22:29
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Compact integrated magnetometer based on nitrogen-vacancy centres in diamond
摘要： We demonstrate an integrated and miniaturised magnetic field sensor based on the negatively charged nitrogen-vacancy centres (NV-) in diamond. The compact device includes all optical components, both for the optical excitation path and for the detection of the emitted fluorescence signal. We experimentally verify that it enables optically detected magnetic resonance (ODMR) measurements and we specify noise and sensitivity of the magnetometer. The minimal detectable magnetic field of the device is ≈ 1 μT for a given integration time of 1 ms, which is approximately one order of magnitude larger than its photon shot-noise limit. It has the significant advantage over traditional setups using NV- centres (including a laser and a complex optical system) that the specific construction volume is about 2.9 cm3 with a total power consumption of ≈ 1.5 W, which enables the device for a wide range of industrial sensing applications.
关键词： synthetic diamond,defects,optical properties,high pressure high temperature (HPHT),sensors
更新于2025-09-23 15:22:29
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CVD diamond film detectors for α particles with a new electrode structure of reduced graphene oxide/Au
摘要： (111)-oriented poly-crystalline diamond ?lms (PCDs) have been deposited on Si substrates by MPCVD technology. The new electrode structure of reduced graphene oxide (RGO)/Au was successfully fabricated onto PCDs. Using the circular transmission line model (CTLM), the contact resistance of 6.6 Ω cm?2 was obtained for RGO/Au electrode on PCD surface, which was notably lower than that of 97.4 Ω cm?2 for Ti/Pt/Au electrode. Furthermore, two detectors with these two type electrodes were made respectively. The dark current, photocurrent and energy resolution of these two detectors under 5.5 MeV α particles irradiation from a 241Am source were observed. The results demonstrated that the fabrication of RGO/Au electrode onto PCD can realize a ?ne ohmic contact. The photocurrent of 58.7 nA for the detector with RGO/Au electrode had higher values than that of 8.8 nA for the detector with Ti/Pt/Au electrode at the bias voltage of 100 V respectively. Due to the realization of good contact on PCD surface with RGO/Au electrode, the energy resolution of 11.9% for the detector with RGO/Au electrode better than that of 24% for the detector with Ti/Pt/Au electrode can be obtained. Fabrication of the RGO/Au electrode on PCD may provide a feasible way to improve its detection performance under α particles irradiation.
关键词： α particle irradiation,Diamond ?lm,Ohmic contact,RGO/Au electrode,Raman spectroscopy
更新于2025-09-23 15:22:29
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Effect of temperature and bias voltage on electrical and electrochemical properties of diamond-like carbon films deposited with HiPIMS
摘要： The relatively high electrical resistivity of diamond-like carbon (DLC) film is one of the main drawbacks when applied in electronic device. In this study, DLC films were synthesized on 304 stainless steels by high power impulse magnetron sputtering (HiPIMS) process and the effect of deposition temperature and bias voltage on the microstructure, electrical and electrochemical properties, hardness and adhesion strength of the DLC films were investigated. The sp2/sp3 ratio of DLC films first decreased then increased and the surface became denser as bias voltage increasing from 0 to -400 V. While the film turned into graphite-like structure and became incompact when deposition temperature rose from 100 °C to 300 °C. The interfacial contact resistance (ICR) got reduced by increasing bias voltage and deposition temperature. However, as the deposition temperature increased to 300 °C the anticorrosion ability and hardness of DLC films deteriorated. The DLC films deposited at 300 °C presented soft and had better adhesion strength than hard DLC films deposited at 100 °C. DLC films deposited at -400 V bias and 300 °C had the lowest ICR while DLC films deposited at -400 V bias and 100 °C had the best performance when ICR, corrosion resistance and hardness were all taken into consideration.
关键词： Electrochemical corrosion,Substrate temperature,High power impulse magnetron sputtering,Interfacial conductivity,Diamond-like carbon,Bias voltages
更新于2025-09-23 15:22:29
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The Effect of Precursor Composition on the Structural Properties of Nanocrystalline Diamond Films
摘要： Nanocrystalline diamond (NCD) films were grown by hot filament CVD and the precursor composition dependence of the structural properties was examined. Films grown at 1 and 2 CH4 Vol% were found to be NCD layers with grain sizes of ～23–25 nm while films grown at 3–5 Vol% were identified as the mixtures of microcrystalline diamond and graphitic phase. The sp2/sp3 bonded carbon ratio in the grown films increased as the CH4 content increased up to 3 Vol% and then decreased beyond 4 Vol%. Microstructure and deposition rate were also found to be affected by the precursor composition and the NCD film grown at 1 CH4 Vol% showed a very dense microstructure and the highest deposition rate of ～3 nm/min.
关键词： Precursor Composition,Structural Properties,Nanocrystalline Diamond
更新于2025-09-23 15:22:29
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Research on Micro-Size Electrical Discharge Machining Polycrystalline Diamond
摘要： With the demand of modern cutting technology for ‘high efficiency, precise, flexibility and green manufacturing’, polycrystalline diamond materials as cutting tools have been widely used in automobile, aerospace and non-metal processing. Electro-spark erosion is one of the most effective ways to machine polycrystalline diamond materials. Single pulse discharge is one of the research foundations of micro-EDM. Using 2 micron granularity polycrystalline diamond as experiment material, the influence of single pulse discharge technology on the removal efficiency of materials was studied, such as pit radius, pit depth and radius-depth ratio, etc. The experimental results show that, with the extension of the pulse duration, the radius of the discharge pit begins to increase rapidly, then slowly increases, and finally to slow down; while the radius of thermal influence zone increases rapidly and then continues to increase slowly. With the extension of pulse duration, the ratio of pit depth to radius changes within the range of 0.05 ~ 0.25, which shows a downward trend basically.
关键词： Single pulse,Micro-size,Polycrystalline diamond (PCD),Electrical Discharge Machining (EDM),Corrosion pit size
更新于2025-09-23 15:22:29
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Modeling and multiresponse optimization of cutting parameters in SPDT of a rigid contact lens polymer using RSM and desirability function
摘要： Amidst different conventional contact lens manufacturing techniques, single-point diamond turning (SPDT) is one of the recently developed ultra-high precision machining techniques employed in the fabrication of advanced contact lenses due to its capability of producing high optical surfaces of complex shapes and nanometric accuracy. SPDT is regarded as an effective process for the generation of high-quality functional surfaces in optical industries. However, despite advances in the ultra-high precision machining, it is not always easy to achieve a high-quality surface finish with maximum productivity. Machining parameters, namely cutting speed, feed rate, and depth of cut, play the lead role in determining the machine economics and quality of machining. The present study focuses on the determination of the optimum cutting conditions leading to minimum surface roughness as well as electrostatic charge and maximum productivity, in SPDT of the polymethyl methacrylate (PMMA) contact lens polymer using monocrystalline diamond cutting tool. The optimization is based on the response surface methodology (RSM) together with the desirability function approach. In addition, a mathematical model is developed for surface roughness (Ra), electrostatic charge (ESC), and material removal rate (MRR) using RSM regression analysis for a rigid contact lens polymer by the Design-Expert software. RSM allowed the optimization of the cutting conditions for minimal surface roughness, electrostatic charge, and maximal material removal rate which provides an effective knowledge base for process parameters, to make its enhancement of process performance in SPDT of contact lens polymer.
关键词： Electrostatic charge,Response surface methodology,Material removal rate,Surface roughness and optimization,PMMA contact lens polymer,Single-point diamond turning
更新于2025-09-23 15:22:29
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Diamond nanofeathers
摘要： This paper reports a special diamond nanostructure which we call diamond nanofeathers (DNFs). The nanostructure was discovered after electrochemically etching doped nanocrystalline diamond (NCD) films. With high resolution SEM, we have repeatedly observed highly porous, fractal-like geometry with “shafts”, “barbs” and “barbules” of the DNFs. A DNF has very high aspect ratio, with a height comparable to the thickness of the etched diamond film and a lateral size as small as several nanometers. This diamond nanostructure seems not to belong to either conventionally defined NCD or ultrananocrystalline diamond (UNCD). The Raman spectra tell that after the electrochemical etch, the DNFs have lower signals from the grain boundaries, compared with the Raman spectra before the etch, which suggests the pores of the DNFs was related with mass loss from the grain boundaries. Preliminary electrochemical characterization has observed more than 300× capacitance increase after the DNFs are fabricated out of a NCD film. With the specific pore size and the ease of fabrication, the DNFs could be a great material choice for supercapacitors, batteries, sensors, and solar cells etc.
关键词： Diamond nanofeathers,Supercapacitors,Nanocrystalline diamond,Raman spectra,Electrochemical etching
更新于2025-09-23 15:21:21
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Simple imaging for the diamond anvil cell: Applications to hard-to-reach places
摘要： The employment of high-pressure gases as a pressure-transmitting medium, sample, or reactant for diamond anvil cell experiments is widespread. As a pressure transmitter, high-pressure gases are crucial to forming quasi-hydrostatic compression atmospheres for samples inside the uniaxially driven cell. We describe an optical design for forming high-resolution images of the gasket and sample chamber of the diamond anvil cell under high gas pressures in a gas loading apparatus. Our design is simple, is of low-cost, and may be easily adapted to suit gas loading apparatus of any design, as well as other common hard-to-reach environments in diamond anvil cell experiments, i.e., those with large stand-off distances, such as cryostats.
关键词： optical design,high-pressure gases,gas loading apparatus,diamond anvil cell,imaging
更新于2025-09-23 15:21:21