Papers by Author: Rong Fa Chen

Abstract: Micro-nanocrystalline diamond (M-NCD) Film may be successfully prepared on Mo substrate with DC arc plasmas jet deposition device. This paper studies the influences of carbon source concentration on the shape of M-NCD Film particles under circumstances of stable electric arc, and characterizes the grain size and quality of samples through SEM, AFM and Raman spectrum. The research result shows that, in the state of stable electric arc, relatively low carbon source concentration (1%) could deposit high-quality microcrystalline diamond film on the substrate, with a growth rate of up to 8.3μm/h and grain size of about 2～4μm; relatively high carbon source concentration (10% or 15%) could deposit high-quality nanocrystalline diamond(NCD) film on the microcrystalline diamond film at high speed, with a growth rate of up to above 12.6μm/h or 19.7μm/h, grain size of about 4～80nm and average grain size of 27.4nm.

Abstract: The abrasive ice disc chemical mechanical polishing (AID-CMP) is a potential polishing process in the semiconductor industry to realize superior surface finish and planarity for semiconductor wafers. In this paper we investigated the temperature field during GaAs wafer AID-CMP process for a better understanding of AID-CMP. The results show that the AID outer temperature is higher than the inner, and the highest temperature in AID is at the wafer/AID contact zone. The increases of Pc, v, eh and tp will generate more energy and cause more local melting during GaAs wafer AID-CMP process. The AID temperature and the area of highest temperature zone increase with increasing Pc, v, and eh. The nodes temperature increase in every conditions adopted as tp increases. The area of melted zone and thickness of melted ice increase with increasing Pc, v, eh and tp.

Abstract: Diamond film was deposited on spherical molybdenum substrate by DC arc plasma CVD method. Diamond film morphology, purities and orientation evolution, obtained from atomic force microscopy, scanning electron microscopy, Raman spectroscopy, X ray diffraction respectively, has showed that grains on the growth surface are compact, continuous and uniform. Characteristic diamond (111), (220), (311) peaks were found and (111) facets were predominant. It revealed that diamond film was polycrystalline texture characteristic. There is a typical diamond Raman spectrum peaks at 1332.0 cm-1, and not graphite and amorphous carbon characteristic peak. High purity diamond film was deposited. When methane concentration was increased, diamond film has more local clusters and vacancy defects such as voids, graphite inclusion, and hydrogen cluster. Therefore, some important parameters such as methane concentration and substrate temperature should be optimized in depositing diamond film.

Abstract: Strain films in the thin film resistance strain gauge are prepared by magnetron sputtering method. Some results concerning the electromechanical and structural properties of nichrome (Ni80Cr20 wt.%) thin films are presented. As compared to the well-known Ni-Cu (constantan) alloy film, which are widely used for manufacturing pressure and force sensors, nichrome (Ni80Cr20 wt.%) thin films exhibit gauge factor values of the same order of magnitude, but they are much more corrosion resistant and adherent to the substrate. The influences of composition and post-deposition annealing on the electrical resistance, temperature coefficient of resistance (TCR) and gauge factor of nichrome (Ni80Cr20 wt.%) thin films are discussed.

Abstract: In this paper, a new polishing technique was proposed to polish concave spherical surface by diamond spherical shell deposited by DC-Plasma Jet CVD(chemical vapor deposition), and preparation was studied from both experiment and theory. The deposited films were investigated by some techniques including: scanning electron microscopy (SEM), atom force microscopy (AFM), Raman spectroscopy, and roughness-profile-meter, which were used to analyze surface phase, microstructure, internal quality and surface roughness. The results show that the deposited diamond spherical shell film has some remarkable properties, such as high surface density, high hardness. Compared to traditional polishing techniques, it will have some potential advantages as convenient, flexible, efficient and precious. To adjust some important parameters as methane concentration, depositing time, and it can deposit the different size grain diamond spherical shell films, which are used to polish different precision degree concave spherical surfaces. Meantime, to change curvature of diamond spherical shell, it can adapt to polish various curvature radius concave spherical surfaces.

Abstract: Diamond spherical shell thick film was prepared by high power DC-plasma jet CVD. Atom force microscopy, scanning electron microscopy, Raman spectroscopy and roughness-profile-meter were used to characterize microstructure, morphology, impurities and orientation evolution of diamond spherical shell thick film. The results show that, when nucleation begins, grains grow random orientation. The grain size of spherical diamond film prepared is compact, clear, uniform, continuous and no remarkable bigger grain over the whole surface of film. On the growth surface, (100) facets were dominant, and the cross-section SEM indicated that film columnar spreading grew from the substrate surface to the diamond film surface. The roughness of the growth surface was much more than that of the nucleation surface. To adjust some important parameters as methane concentrate, depositing time, and matrix temperature, and high quality diamond spherical shell thick film was deposited.

Abstract: Hardness, elastic modulus and scratch resistance of single silicon wafer are measured by nanoindentation and nanoscratching using a nanoindenter. Fracture toughness is measured by indentation using a Vickers indenter. The results show that the hardness and elastic modulus at a peak indentation depth of 100 nm are 12.6 and 166.5 GPa respectively. These values reflect the properties of the silicon wafer, the bulk material. The fracture toughness value of the silicon wafer is 0.74 Mpa·m1/2. The material removal mechanisms are seen to be directly related to the normal force on the tip. The critical load and scratch depth estimated from the scratch depth profile after the scratching and the friction profile are 138.64 mN and 54.63 nm respectively. If the load and scratch depth are under the critical values, the silicon wafer will undergo plastic flow rather than fracture. The critical scratch depth is different from that calculated from the formula of critical-depth-of-cut described by Bifnao et al and some reasons are given.

Abstract: Chemical vapor deposited (CVD) diamond film is a good materials for cutting tools as its a series of excellent properties. But because of its polycrystalline morphology, CVD diamond thick film has a rough surface that limits its application in engineering. In this paper, study was carried out on the mechanical lapping of diamond film. It is shown that surface roughness of the film was reduced from Ra 4.5μm to Ra 0.2μm after 50-minute polishing. The surface integrity of polished diamond thick film was investigated, which includes surface roughness, morphology and residual stress. There are a lot of micro defects such as grooves, gas cavities and micro cracks on the polished surface, which are the intrinsic defects generated in the deposition process of CVD diamond film. The tensile stress of the film reduced through polishing as the release of the deformation energy stored in the film.

Abstract: In the present work, high power DC arc plasma jet chemical vapor deposition (CVD) is used to prepare diamond films with full width half magnitude (FWHM) less than 10 wave numbers at 1332 cm−1 Raman peak. During the polishing process, diamond film is hold against the stainless steel holder, which rotates and swings when the sample comes into contact with the cast-iron plate. Average surface roughness of the forming nucleus polished surface and growing polished surface is 560nm, 90nm respectively. And the materials removal rate is quite different. Fine crystal grain of the forming nucleus surface and the thick column crystal of growing surface are dominant in structure. In the meantime, effects of the size of the abrasive power, the applied force and polishing direction are also discussed. A profilometer, an Raman spectroscopy, X-ray diffraction and a scanning electron microscope have been used to evaluate the surface states of diamond films before and after polishing. This result reveals an. improvement of polishing efficiency and a great potential for commercial application.

Abstract: Although research on various diamond polishing techniques has been carried for years, some issues still need to be examined in order to facilitate application on large areas in a cost-efficient manner. A compositive technique for machining efficiently thick diamond films prepared by DC plasma arc jet is reported in the present paper. A two-stage polishing was applied on thick polycrystalline diamond films, by employing first electro-discharge machining (EDM) for rough polishing and subsequently mechanical polishing for finishing operations. Experimental results obtained clearly indicate the applicability of the proposed two-stage technique for fabricating transparent diamond films that can be used for the production of X-ray windows. Appropriate etching with EDM is an effective pretreatment method for enhancing the efficiency of rough polishing process in mechanical polishing of thick diamond film. The machined surfaces of diamond films are studied by Scanning Electron Microscope (SEM) and Raman Scattering Spectroscopy (Raman).