Materials Science Forum Vols. 561-565

Abstract: AlN thin films have been deposited on p-(100) Si and glass substrates by pulsed bias arc ion plating at different negative substrate biases. The crystal orientation, deposition rate and mechanical property of the films were investigated by X-ray diffraction, nanoindenter and UV-VIS spectrophotometer. The results reveal that pulsed bias has a large influence on film preferred orientation, deposition rate and mechanical property. A preferred (110) orientation is observed in the film deposited at a bias of -50V. With the increase of the bias, film deposition rate decreases first sharply then wildly; Film hardness and elastic modulus first increase, then decrease and finally increases. Higher value of film harness obtained at the bias of -50V and -500V relates to the (110) preferred orientation and grain refinement respectively.

Abstract: Fe/Si multi-layer films were fabricated on Si (100) substrates utilizing radio frequency magnetron sputtering system. Si/β-FeSi2 structure was found in the films after the deposition. Structural characterization of Fe-silicide sample was performed by transmission electron microscopy, to explore the dependence of the microstructure of β-FeSi2 film on the preparation parameters. It was found that β-FeSi2 particles were formed after the deposition without annealing, whose size is less than 20nm ,with a direct band-gap of 0.94eV in room temperature. After annealing at 850°C, particles grow lager, however the stability of thin films was still good.

Abstract: The TFTs array fabrication process for large-area TFT-LCD has been continuously developed for simplifying processing steps, improving performance and reducing cost in the process of mass production. In this study, the hydrogenated amorphous silicon (a-Si:H) TFTs with low resistivity electrodes , silver thin films, were prepared by using the selective deposition method that combined lift-off and electroless plated processes. This developed process can direct pattern the electrode of transistor devices without the etching process and provide ease processing steps. The as-deposited Ag films were annealed at 200 oC for 10 minutes under N2 atmosphere. The results shows that the adhesion properties can be enhanced and the resistivity has been improved from 6.0 μ,-cm, significantly decrease by 35%, of as-deposited Ag films by annealed. The thickness of Ag thin film is about 100 nm and the r. m. s roughness value is 1.54 nm. The a-Si:H TFT with Ag thin films as source and drain electrodes had a field effect mobility of 0.18 cm2/Vs, a threshold voltage of 2.65 V, and an on/off ratio of 3×104.

Abstract: The image of thermal spray splats is difficult to collect due to its high velocity of droplets. Especial in High Velocity Oxy-Fuel (HVOF) process, the process present higher velocity of flame jet correlated to other thermal spray process. The system presents at this article describes a useful splats catching method to obtaining splats during thermal spray deposited. Capabilities and advantages of using this instrument are declared at this theme. The final result presented the instrument caught the single spot of HVOF sprayed splats at sub-micro second. Splats of spot were dispersed well on the glass substrate at the obtaining system, and presented various information of droplets impact at different location on the substrate.

Abstract: This paper reports that ZnO:Al films were deposited onto glass substrates by sol-gel process. Al/Zn atomic ratio varied in a wide range from 0 ~ 20%. The structural and optical properties were investigated by X-ray diffraction (XRD) and optical transmittance, respectively. X-ray photoemission spectroscopy (XPS) was used to investigate the elemental compositions. XRD results showed that ZnO films remained c-axis-orientated when Al/Zn atomic ratio was below 20% and the grain size decreased with increasing Al content. The optical transmittance showed that the optical bandgap of ZnO films blueshifted with increasing Al/Zn atomic ratio from 0-20%. XPS measurements showed that the binding energy of O1s increased with increasing Al content.

Abstract: TiC/a:C nanocomposite thin film has proven to be a worthy material selection as a thin film for tribological applications due to its low coefficient of friction, good wear resistance and high hardness. In the current study TiC/a:C thin films with carbon concentration near 55-62 at % were deposited via pulsed closed field unbalanced magnetron sputtering (P-CFUBMS) in pure argon atmosphere with different substrate bias voltages and onto 440C stainless steel substrate with different substrate roughness. It was found that the TiC/a:C film hardness and elastic modulus were increased from 18.5 GPa to 33.8 GPa by increasing the substrate bias from floating to -150 V. However higher substrate bias can also decrease the film tibological properties. The substrate roughness has a strong effect on TiC/a:C film wear behavior. When the Ra (Mean surface roughness values) is less than 110 nm, the COF values are in low range (0.18-0.28). Further increase the Ra value to above 300 nm will result in a higher COF (>0.33). Films deposited on higher surface roughness substrate need longer time to reach the sliding equilibrium state.

Abstract: In this work, we investigated the deposition of the AlN thin films on silicon (100) substrates by mid-frequency pulsed magnetron sputtering of a metal Al target in an Ar-N2 gas mixture at room temperature. The films were characterized by various means for the composition, the crystal structure, the surface morphology, and the hardness and Young’s modulus. AFM surface RMS (root mean square) roughness analysis revealed that the surface morphology has relation with the nitrogen flow rate in the Ar–N2 gas mixture. The highest surface smoothness was observed at the nitrogen flow rate of 30-50%. The phenomenon was interpreted by the action of the vapor-solid interface on the film growth, as well as the nonequilibrium processes occurred in the film growth.

Abstract: This study explores the dynamic mechanical properties (e.g., storage shear modulus, loss tangent and shear viscosity) and formability of a polyimide film by visco-elasticity measurement and hot-embossing tests. The variations of storage shear modulus, tangent delta and the shear viscosity were measured as a function of the temperature for two frequencies. As a polyimide goes through its glass transition, it exhibits dramatic decreases in shear modulus and viscosity as well as the peak of tangent delta, and continues to show strong dependence on frequency and temperature. Moreover, the filling characteristics (e.g., surface appearance, replicated depth and surface roughness) of polyimide were investigated by hot-embossing tests at different temperatures using a mold with an aspect ratio of 2.5:1.

Abstract: The DMS GaMnN film with certain concentration of Mn and good crystal qualities has been successfully grown on the substrate of sapphire (α-Al2O3) by ECR-PEMOCVD. The graphs of RHEED presented a clear spot-like lattice and the surface was not very glossy, which showed that the GaMnN film was single crystalline and its growth model was three -dimensional island. XRD analysis showed that the film was hexagonal structure with c -Axis oriented and the crystallinity was very well. The AFM test result showed that the GaMnN films were composed of many submicron grains with the same orientation. SQUID(superconducting quantum interference device) measurement showed an apparent ferromagnetic hysteresis at room temperature, and the Curie temperature of the film was about 400k.