Abstract: To investigate the effects of film thickness on Raman characterization and intrinsic stress of tetrahedral amorphous carbon and ascertain the correlations between stress and Raman spectra, the ta-C films with different film thickness were deposited on the polished P-type (100) c-silicon substrate with the same conditions by the filtered cathodic vacuum arc technology. The film thickness
was measured by the surface profiler and the atomic force microscope; stress was calculated according to the curvature of the stress samples examined by the surface profiler; the microstructure of the films was characterized by the Ramanscope. It has been shown that the stress drops down continuously and the dropping rate turns mild with the increase of film thickness. When the film
thickness surpasses 30 nm, the compressive stress is kept at less than 5 GPa. The intensity of the first and second order peak of the c-Si substrate in the visible Raman spectra gradually depresses with the increase of thickness. However, the FWHM is minimal and the maximal intensity is highest from 50 nm to 80 nm, accordingly the clearest Raman signals can be acquired in this scale. Additionally, the position of the asymmetric broad peak gradually shifts towards the lower wavenumber with the increase of thickness and the decease of intrinsic stress.
Abstract: DLC and nanocrystalline diamond films were prepared by PLD process using 308
nm(XeCl) laser beam with high power(200-500 W) and high frequency(200-500 Hz). The effects of some parameters such as the laser power density, the repetition rate on the structures and characters of the DLC films under such extreme power and repetition rate conditions were studied for the first
time. The results indicated that: (1) The microstructures of the films were varied from amorphous to nanocrystalline with the laser power density increased from 108 W/cm2 to 1010 W/cm2; (2) The properties of the films grew at 200 Hz and 300 Hz were better than that of the films grew at 500 Hz, with the laser power density remained constant at 1010 W/cm2.
Abstract: Diamond and B4C coatings were used as an interlayer for the growth of cubic boron
nitride thin films on c-silicon. By employing a B-C-N gradient layer on top of the B4C interlayer, improved adhesion occured between BN and B4C. A multi-step process after the nucleation of c-BN was found very helpful for improving the adhesion of c-BN on silicon with interlayers. Residual stress of c-BN thin film was significantly decreased by using a new post-deposition annealing treatment.
Abstract: The reaction induced phase separation aimed for the distribution of nano-structured particles has been investigated by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) in ternary Ti-Si-N film via N+ implantation. The fabrication of Ti-20at%Si film has made on Si substrates by ion beam sputtering (IBS), and then N+ implantation with 50 keV has been conducted on these films. The selected area electron diffraction (SAED) from as-deposited film shows amorphous Ti-Si. As-deposited Ti-Si film exhibited high stability even for the heat treatment at 773K for 3600s. N+ implantation induced the direct formation of nano crystalline of fcc-TiNx within the Ti-Si film. The XPS depth profiling and chemical shift suggest that the preferential nitriding of Ti accompanied with the segregation of SiNx occurred during N-implantation.
Abstract: Fatigue damage behaviour in micron and sub-micron thick Cu films has been
investigated using focused ion beam (FIB) microscopy and transmission electron microscopy (TEM). The observations show that cyclic strain localization in the fatigued thin films is affected by the physical dimensions of the material, as evidenced by changes in the extrusion dimensions and by changes in the dislocation structures. The significant decrease in extrusion dimensions and the
suppression of the development of bulk-like dislocation structures with decreasing film thickness and grain size is attributed to the strong inhibition of dislocation mobility and activity at small length scales.
Abstract: The reaction induced phase separation aimed for the distribution of nano-structured
particles has been investigated by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) in ternary Ti-Si-N film via N+ implantation. The fabrication of Ti-20at%Si film has made on Si substrates by ion beam sputtering (IBS), and then N+ implantation with 50 keV has been conducted on these films. The selected area electron diffraction (SAED) from as-deposited film shows amorphous Ti-Si. As-deposited Ti-Si film exhibited high stability even for the heat treatment at 773K for 3600s. N+ implantation induced the direct formation of nano crystalline of fcc-TiNx within the Ti-Si film. The XPS depth profiling and chemical shift suggest that the preferential nitriding of Ti accompanied with
the segregation of SiNx occurred during N-implantation.
Abstract: TiC/a-C:H nanocomposite coatings have been deposited by magnetron sputtering and are composed of 2-5nm TiC nanocrystallites well separated by amorphous hydrocarbon (a-C:H) of about 2nm separation width. A transition from columnar to glassy microstructure has been observed with increasing substrate bias or carbon content. Micro-cracks induced by nanoindentation or wear
tests readily propagate through the column boundaries whereas the coatings without a columnar microstructure show supertough behavior. The nanocomposite coatings exhibit hardness of 5~20 GPa, superior wear resistance and strong self-lubrication effects with a friction coefficient of 0.05 in air and 0.01 in nitrogen under dry sliding against uncoated bearing steel balls. Especially, the transitions from low to ultralow friction or the reverse are repeatedly switchable if the atmosphere is
cycled between ambient air and nitrogen. The lowest wear rate is obtained at high humidity.
Abstract: The mechanical properties of the molecular deposition film deposited on an Au substrate are studied in the theory for the first time. Firstly, the quantum mechanics have been used to calculate the structure parameters and potential parameters of the molecular deposition film. Secondly, molecular dynamics simulations have been used to study indent process of the molecular deposition film with the action of Au tip. The results showed that an obvious jump to contact appears during the Au tip approaches the molecular deposition film; furthermore, the tilt angle and
load of the molecules near the tip have the same tendency of hysteresis, which may be caused by the adhesive force between the tip and the molecular deposition film.
Abstract: A special phenomenon, anisotropic diffusion is observed during plasma-assisted nitriding of a nickel-based alloy, Inconel 690. The diffusion rate is found to be higher in grains with an orientation close to <100> than in those grains with an orientation close to <111>. A model is established basing on the anisotropic strain and stress during nitriding so as to explain this phenomenon. It is shown that, the anisotropic stress in this f.c.c. alloy causes the different activation energy of N on various grain orientations, and finally result in the anisotropic diffusion rate of N in the alloy. Based on this model, a good agreement between calculated results and experimental results is obtained for temperatures below 400 °C.