Papers by Keyword: HFCVD

Abstract: Analysis of hot-filament CVD (HF-CVD) growth of high quality 3C-SiC on micron-sized 3C-SiC mesas is presented. Two types of growth were observed: 1) a relatively slow growth at about 1μm/hour, and 2) an almost three times faster growth, correlated with the presence of domain boundaries in, or adjacent to, the mesas. Both reveal well-defined crystallographic facets and sharp corners between them. The slower growth has been identified to be surface-nucleation-limited, seemingly defect-free, while the faster growth has been identified as being caused by defect-induced step-flow growth. A growth model is presented, yielding a growth rate of 1.18 μm/h for the defect free {111} and (100) plane and 2.8 μm/h for {110} planes.

Abstract: Cutting tools of WC-Co are widely used in cutting field. Nevertheless, its wear resistance and lifetime are not qualified for the high performance cutting. Therefore, diamond films are deposited on WC-Co substrates to overcome its disadvantages. In this paper we investigate the effects of the pretreatment on substrates and as-deposited WC-Co samples by using a hot filament chemical vapor deposition (HFCVD) reactor. Prior to deposition, the WC-Co substrates were submitted to surface roughening by Murakami reagent and to surface binder removal by Caro’ acid with varied durations. Surface roughness R_a determined by AFM varied from 110 to 279 nm. The diamond films are characterized by scanning electron microscopy (SEM) and Raman spectroscopy, whose results present a sharp peak at 1336 cm^-1 indicating sp³ diamond. The adhesion between the diamond films and substrates was evaluated by pull-off tests with the highest adhesion strength is 26.92 MPa. Cracked interface is characterized between diamond films and substrates, using SEM and energy dispersive spectroscopy (EDS) to analyze the adhesion performance.

Abstract: The effect of argon content upon the growth rate and the properties of diamond thin films grown with different grains sizes are explored. An argon-free and argon-rich gas mixture of methane and hydrogen is used in a hot filament chemical vapor deposition reactor. Characterization of the films is accomplished by scanning electron microscopy, Raman spectroscopy and high-resolution x-ray diffraction. An extensive comparison of the growth rate values and films morphologies obtained in this study with those found in the literature suggests that there are distinct common trends for microcrystalline and nanocrystalline diamond growth, despite a large variation in the gas mixture composition. Included is a discussion of the possible reasons for these observations.

Abstract: The purpose of this work is to study the structural and morphological modification of the surface of the n-type diamond electrodes as a function of nitrogen doping. The characterizations of these electrodes were made using Raman Spectroscopy, Contact Angle, X-ray diffraction and Scanning Electron Microscopy (SEM). The nitrogen-doped diamond (NDD) electrodes were produced using Hot Filament-assisted Chemical Vapor Deposition method (HFCVD) from methane, hydrogen and nitrogen in the gas mixture. The results from Raman spectroscopy show that the diamond films obtained with nitrogen addition presented one large band at 1100-1700 cm^-1. The SEM images showed that the variation in the nitrogen doping influenced the growth rate of films by promoting changes in the sizes of grains from microcrystalline to nanocrystalline texture. This behavior supported the results obtained from X-ray diffraction analyses. It was possible to verify a decrease in the crystallite size as a function of the nitrogen increase.

Abstract: This is a comparative experimental study of the micro, nanoand ultranano-crystalline diamond deposition. The Hot Filament Chemical Vapor Deposition (HFCVD) reactor deposits the films using different deposition parameters. Scanning Electron Microscopy and Field Emission Scanning Electron Microscopy let morphology inspection. Visible-Raman scattering loaded to estimating relative induced stress, by the graphite peak shift and associated with the defect incorporation and sp² bond enhancement. The x-ray diffraction confirmed the diamond crystallinity, where Scherrer ́s equations estimate crystallite size and diamond renucleation rates. In this work we propose a defect increasing relative graphite incorporation with the transition of micro, nanoto ultranano-crystalline diamond deposition. Besides this, we propose that this increase defects follows the increase diamond renucleation rates and decreases in the induced stress films. Included is a discussion of the possible reasons for these observations.

Abstract: In the process of HFCVD diamond film growth on the multitudinous micro end mills, the uniformity and stability of the temperature distribution have a vital importance on the quality of film. So a new method by using the finite volume is proposed to analyze the importance of different disposition parameters on the uniformity of substrate temperature field. These parameters are filament diameter (d), filament-substrate distance (H), filament separation (S) and filament length (L). The mono-factor method are used to optimize the best parameter combination. The simulation results show that the optimized parameters are d=0.65mm, H=10mm, S=27mm and L=160mm.

Abstract: The uniform temperature flied of substrates is a key factor to deposit high-quality diamond films on milling tools by the hot filament chemical vapor deposition (HFCVD). In this study, a 3-D computational model is established to simulate the temperature distribution on the substrates. Thereafter, the influence of the rotational speed of worktable n and the water flux of water-cooled worktable Q are investigated. The simulation results show that the increasing of the rotational speed of worktable is suitable to grow homogeneous diamond films and gently decrease the even temperature of seals. What’s more, the deceasing of the water flux will significantly increase the overall temperature of seals.

Abstract: Bias voltage assisted hot filament chemical vapor deposition (HFCVD) was adopted to deposit boron-doped diamond (BDD) film on porous titanium substrate, and diamond composite membrane materials were prepared and characterized by X-ray diffraction method. The influence of carbon concentration, boron source concentration, substrate temperature were discussed respectively on the diamond quality and the transition layer TiC. Results showed that: The concentration of carbon source was related to crystal orientation and the growth rate of diamond. The increase of diamond nucleation density and growth rate prevented the formation of TiC, and improved adhesion between diamond and the substrate; The increasing of boron source concentration promoted the orientation growth of diamond film (111) lattice plane, while reduced the content of TiC; Temperature affected the formation of TiC, and TiC diffraction peaks intensity decreased with the increase of substrate temperature; As the substrate temperature increased, secondary nucleation rate caused cauliflower-like structure which dominated growth mechanism transitting from MCD (Microcrystalline diamond) to the NCD (Nanocrystalline diamond).

Abstract: Microcrystalline diamond (MCD), nanocrystalline diamond (NCD) and microcrystalline and nanocrystalline composite diamond (MNCD) films are all deposited on flat square shaped WC-6%Co substrates by using bias-enhanced hot filament chemical vapor deposition (HFCVD) apparatus. The diamond films are characterized with scanning electron microscope (SEM) and Raman spectrum. Typical diamond film features are exhibited in the observation of SEM and the analysis results of Raman spectrum. The tribological properties of diamond films against zirconia ceramic are conducted on a ball-on-plate type rotating reciprocating tribometer in ambient air. The average friction coefficients of MCD, NCD and MNCD film in stable period are 0.205, 0.181 and 0.138 respectively. The images of surface topography based on white-light interferometer suggest a very low wear rate of CVD diamond film.

Abstract: In the present investigation, both micro-crystalline and nanocrystalline diamond (MCD and NCD) films are fabricated, which are characterized by FESEM (Field Emission Scanning Electron Microscopy), surface profilemeter, Raman spectroscopy and Rockwell hardness tester. Moreover, under the dry environment, the frictional behavior of both the films sliding against commonly-used materials in the metal drawing industry is studied on a ball-on-plate rotational frictional tester, including the stainless steel, low-carbon steel, high-carbon steel and copper, demonstrating that the frictional coefficients between NCD films and all these materials are relatively smaller. Furthermore, the wear rates of both the films, which are hardly measured in the ball-on-plate friction tests, are evaluated using a home-made inner-hole line drawing apparatus, with both the diamond films deposited on the inner-hole surfaces and the low-carbon steel wires as the counterparts. Inversely, the NCD films present higher wear rates than the MCD ones, which can be attributed to the deteriorative film purity and adhesion.