Search

The aim of this work is to study and model the effect of argon addition to the N 2 working gas on the intrinsic stress of TiN coatings deposited via rectilinear filtered vacuum arc plasma using substrate pulse bias potential. It was found that produced TiN coatings have a NaCl type cubic structure with the [110] axial texture regardless of the concentration of argon in the gas mixture. With increasing the content of argon in the gas mixture, the level of residual stress increased from 7 GPa up to 10 GPa and the coatings hardness remained at a high level of 27–32 GPa. By mathematical modeling based on the modified Davis model, it was shown that increasing the stress level in the TiN coatings with increasing of argon content was due to the intensification of the bombardment process of the coating surface by the inert gas ions. [ABSTRACT FROM AUTHOR]

In order to obtain super-hard films with excellent mechanical and tribological properties, diamond-like carbon (DLC) films were prepared on ultra-fine grained cemented carbide substrates by linear magnetic filtered arc ion plating (AIP) under different negative pulsed bias voltages. The result indicated that the pulsed bias voltage had a strong effect on the structure and properties of DLC films. The as-deposited films showed very smooth surfaces because of the magnetic filtration system. Upon increasing the bias voltage from 0 to −1000 V, the fraction of sp3 bonds first increased and then decreased, while the ratio I D / I G exhibited the opposite tendency. The maximum sp3 bond fraction of 74.4 % was determined at −200 V, resulting in the highest hardness, elastic modulus, and elastic recovery of the films. Furthermore, the films exhibited excellent tribological properties with the lowest friction coefficient of 0.073 at −200 V, which was associated with the super-high hardness and low surface roughness. The improved mechanical and tribological properties of DLC films could be achieved by using the appropriate pulsed bias voltage. [Display omitted] • The super-hard DLC films were successfully developed by arc ion plating with the pulsed substrate bias. • The arc deposited DLC films exhibited the smooth and dense surface because of the synergy effect of macroparticle filtering and re-sputtering • The maximum hardness and excellent tribological properties were obtained at – 200 V. [ABSTRACT FROM AUTHOR]

We have investigated the effects of the frequency of pulsed substrate bias on the structure and properties of Si-doped diamond-like carbon (Si-DLC) films deposited by radio-frequency plasma-enhanced chemical vapor deposition using CH 4 , Ar, and monomethylsilane (CH 3 SiH 3 ) as the Si source. The Si/(Si + C) ratios in the Si-DLC films deposited using pulsed bias were higher than that of the dc-biased Si-DLC film, and the Si fraction increased with decreasing frequency. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses revealed that Si–C, Si–H n , and C–H n bonds in the Si-DLC films increased with decreasing frequency. The internal stress decreased as the frequency decreased, which is probably due to the increase in Si–C, Si–H n , and C–H n bonds in the films. It was found that the wear rate of the pulse-biased Si-DLC film deposited at the highest frequency in this study is comparable to that of the dc-biased, undoped DLC film. Furthermore, the friction coefficient of the former is about one third of that of the latter. [ABSTRACT FROM AUTHOR]

Abstract: We have investigated the influence of the duty ratio of pulsed substrate bias on the structure and properties of Si-doped diamond-like carbon (Si-DLC) films deposited by radio frequency plasma-enhanced chemical vapor deposition using CH4, Ar, and monomethylsilane (CH3SiH3) as the Si source. The Si/(Si+C) ratios in the Si-DLC films deposited using pulsed bias were higher than that of the dc-biased Si-DLC film, and the Si fraction increased with decreasing pulse duty ratio. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses revealed that Si-C, Si-Hn, and C-Hn bonds in the Si-DLC films increased with decreasing duty ratio. The internal stress decreased as the duty ratio decreased, which is probably due to the increase in Si-C, Si-Hn, and C-Hn bonds in the films. The Si-DLC films deposited using pulsed bias had higher adhesion strength than the dc-biased Si-DLC film because of the further reduction of internal stress. At higher duty ratios, although the Si fractions of the pulse-biased Si-DLC films were higher than that of the dc-biased Si-DLC film, the wear rates of the former were less than that of the latter. [Copyright &y& Elsevier]

Abstract: Amorphous silicon nitride (a-SiN x ) thin films were fabricated by pulsed reactive closed-field unbalanced magnetron sputtering ultra-high purity n-type single crystal silicon in Ar–N2 mixtures. The effect of N2 fraction on the discharge behavior, deposition rate, composition, chemical bonding configurations, surface morphology, nano-hardness, elastic modulus and optical band gap were primarily investigated. It was found that good stability of reactive sputtering process was maintained by the adoption of the bipolar pulsed magnetron power supply with 180° out-of-phase and the pulsed substrate bias. The arc events and the disappearing anode effect in DC reactive magnetron sputtering of a-SiN x films were prevented. A higher deposition rate (>20 nm/min) for a-SiN x films was achieved. The radical transition of the sputtering mode leads to the deposition rate initially decreased dramatically and then slowly with the increase of N2 fraction. N to Si atomic ratio (N/Si) gradually increased and N is preferentially incorporated in its NSi3 stoichiometric ratio configuration and the Si–N network followed a tendency to tetrahedral chemical order with the increase of N2 fraction in the inlet gases. The a-SiN x films deposited at high N2 fraction were consistently N-rich. The film surface microstructure was transformed from coarse granular mounds surrounded by tiny micro-void regions to homogeneous, continuous, dense and slender hills, as well as a progressive densification and refinement of the film microstructure occurs as the N2 fraction is increased. With the increase of the N/Si atomic ratio, the resistance of the a-SiN x films surface region to plastic deformation improved; hardness and elastic modulus increased, correspondingly. The as-sputtered a-SiN x films exhibit good optical transparency in visible region and the optical band gap E opt can be varied in a broad range of 1.70–3.62 eV depending on the N2 fraction in Ar–N2 mixtures. The increment of optical band gap E opt of the as-sputtered a-SiN x films is determined primarily by the recession of the valence band maximum. [Copyright &y& Elsevier]

• Investigation of a CrAlN process on an industrial scale coating unit. • Analysis of a coating process using a pulsed substrate bias. • Correlation of plasma and coating properties. • Comparison of CrAlN processes using continuous and pulsed substrate bias. In a high power pulsed magnetron sputtering (HPPMS) process a substrate bias is applied to affect the ions in the coating chamber and therefore the coating properties. For this reason the present experiments on an industrial scale coating unit are focusing on the identification of correlations between plasma and coating properties for a CrAlN process while using a pulsed substrate bias. The measurements regarding the plasma properties were carried out on the substrate side for a better understanding of the interaction of plasma and coating properties. These investigations should point out the significant potential of plasma diagnostics for measuring plasma properties to contribute to improved coating processes using pulsed substrate bias U B,p. For this purpose a substrate bias synchronized to the HPPMS pulse is used since the pulsed bias can influence ions of a specific species. It was found that the even low values of a pulsed substrate bias lead to high values of the Debye sheath thickness and thus to a shielding of opposite surfaces. For complex shaped substrates like cemented carbide cutting inserts a better coatability for pulsed substrate bias up to U B, p = -150 V was reached. Also increased values of the mean ion energy and the ion flux density were found compared to the use of a continuous substrate bias. Regarding the chemical composition a significant higher nitrogen content of the coatings was found when using a pulsed substrate bias compared to the use of a continuous substrate bias. Comparing the indentation hardness of a process using a pulsed substrate bias increased hardness values were found compared to the use of a continuous substrate bias. Generally, a significant change of both, plasma and coating properties was found when changing the mode of substrate bias. [ABSTRACT FROM AUTHOR]