Papers by Keyword: Substrate Bias

Abstract: While matrix coated fiber method is used to fabricate SiC continuous fiber reinforced TC17 (Ti-5Al-2Sn-2Zr-4Mo-4Cr) matrix composites (SiC_f/TC17), the properties of SiC_f/TC17 composite are strongly affected by the microstructure and properties of TC17 alloy coatings in precursor wires. In this work, V_b(substrate bias) was adopted to tailor the microstructure and properties of TC17 coatings, and V_b dependent on microstructure, morphology, composition, stress, hardness and adhesion for TC17 coatings have been investigated by X-ray diffraction, scanning electron microscope, atomic force microscope, auger electron spectrometer, surface profiler and nanoindenter. The experimental results showed that all coatings crystallized with hexagonal structure (α-Ti). The migratory ability of incoming ions increased with increasing V_b from floating to-120V, and the smoothing growth surface and re-sputtering came into prominence with further increasing V_b, then the surface roughened again and accompanied by a transition of growth mode from column grains to compact-grain structures. As V_b increased, Al content increased while Ti content decreases. In addition, compressive stress and hardness showed a rising trend caused by ions implantation. Interface ions implantation and stress state acted together on the adhesive force between TC17 alloy coatings and SiC fiber.

Abstract: W-doped VO₂ films were prepared by DC reactive magnetron sputtering with various substrate bias. The microstructure, surface morphology, electrical and optical performances of the films were characterized by x-ray diffraction, scanning electron microscope, four-point probe method and spectrophotometer, respectively. The effect of substrate bias on microstructure, electrical and optical properties of sputtered W-doped VO₂ films was studied. The XRD results reveal that all samples exhibit preferential VO₂ (011) lattice orientation except the as-grown sample in our experiment. All the samples applied substrate bias show some degree optical switching performance in IR range, while the thermochromic phenomena was observed from resistance-temperature dependence plot only for the samples of substrate bias varied from-100V to-200V. This indicate that the optical and electrical properties of W-doped VO₂ films have different sensitivity to substrate bias. Optimal substrate bias of-200V sample shows fine semiconductor-metal-transition performance.

Abstract: Two series of TiAlN and Ti₃AlN films have been deposited on Si (100) substrates by reactive magnetron sputtering TiAl and Ti₃Al targets in Ar/N₂ mixture. The effects of incoming ions energies controlled by V_b on the microstructure, morphologies, residual stress and hardness have been explored by XRD, SEM, AFM, surface profiler and nanoindentation. The results showed that single phase cubic Ti-Al-N solid solubility formed by Al atoms replacing some Ti atoms in the cubic TiN lattice occured in both TiAlN and Ti₃AlN films. As substrate bias increased, the preferred orientation firstly changed from (111) to (200), and then returned to (111) at higher substrate bias. At the same time, high substrate bias promoted the densification of films and presence of high compressive stress, which is benefit for improvement of hardness.

Abstract: The effect of physical and technological factors on the effectiveness of the exchange coupling in two-layer film structures such as Fe₂₀Ni₈₀/Fe₅₀Mn₅₀ has been investigated. The dependences of the coercive force and the exchange bias field of permalloy layer on presence of a buffer Ta layer and its thickness, the order of sputtering and the thickness of Fe₂₀Ni₈₀ and Fe₅₀Mn₅₀ layers, substrate temperature and the features of radio-frequency (RF) substrate bias during deposition were investigated. It has been found that the substrate RF bias improves homogeneity of microstructure and reduces the surface roughness of permalloy layer. This in turn increases the magnetic pinning of permalloy layer and creates the prerequisites for the practical application of layered structures with higher thickness of the ferromagnetic layers.

Abstract: 82% Ni-Fe films have been prepared using Radio frequency (R.F) sputtered, R.F induced substrate bias. The results presented are of study of sputter films deposition at various RF substrate bias conditions so that suitable sputtering rate with optimum (target) composition could be determined for magnetoresistive sensing applications. Films have been sputtered with substrate temperature of 200^° C, sputter gas (argon) pressure of 10mTorr with film thicknesses near 1000 ^°A. Substrate bias potential in the range 0 V to -400 V is varied in order to determine its dependence upon film composition and deposition rate. The result presented indicates the strong bias dependence upon film composition and deposition rate with most useful films for the application in concern could be produced at substrate bias potential in the range of -80 V to -120 V.

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.