When depositing films on a complex workpiece surface by magnetron sputtering, the shadow effect occurs and causes the columnar structure to tilt toward the substrate owing to the oblique incident angle of the plasma flux, affecting the microstructure and properties of the films. Improving the surface diffusion could alleviate the shadow effect, whereas changing the energy of the deposited particles could improve surface diffusion. Different substrate conductivities could affect the energy of the deposited particles when they reach the substrate. In this study, Si (semiconductor) and SiO2 (insulator) sheets are mounted on the inner surface of a hemispherical workpiece, and Ti films with different thicknesses (adjusted by the deposition time) are deposited on the inner surface of the hemispherical workpiece by direct current magnetron sputtering. The results show that there is a threshold thickness and incident angle before the films are affected by the shadow effect. The threshold could be affected by the film thickness, the incident angle, and the conductivity of the substrate. The threshold would decrease as the film thickness or incidence angle increased or the conductivity of the substrate decreased. When the film thickness or incident angle does not reach the threshold, the film would not be affected by the shadow effect. In addition, the film deposited later would tilt the vertical columnar structure of the film deposited earlier. Owing to the different conductivities, the shadow effect manifest earlier for Ti films deposited on the insulator SiO2 than for films deposited on the semiconductor Si when the film thickness is >500 nm.
Titanium nitride (Ti-N) thin films are electrically and thermally conductive and have high hardness and corrosion resistance. Dense and defect-free Ti-N thin films have been widely used in the surface modification of cutting tools, wear resistance components, medical implantation devices, and microelectronics. In this study, Ti-N thin films were deposited by high power pulsed magnetron sputtering (HPPMS) and their plasma characteristics were analyzed. The ion energy of Ti species was varied by adjusting the substrate bias voltage, and its effect on the microstructure, residual stress, and adhesion of the thin films were studied. The results show that after the introduction of nitrogen gas, a Ti-N compound layer was formed on the surface of the Ti target, which resulted in an increase in the Ti target discharge peak power. In addition, the total flux of the Ti species decreased, and the ratio of the Ti ions increased. The Ti-N thin film deposited by HPPMS was dense and defect-free. When the energy of the Ti ions was increased, the grain size and surface roughness of the Ti-N film decreased, the residual stress increased, and the adhesion strength of the Ti-N thin film decreased.
The wide application of Mg alloys has been restricted because of their poor corrosion and wear resistance. Titanium nitride ceramic films prepared via magnetron sputtering can improve the corrosion and wear resistance of Mg alloys. However, residual stress produced at the interface between the film and the Mg alloy substrate causes the TiN film to spall off and reduces its service life. One potential approach to mitigating residual stress involves enhancing the adhesive strength between the film and the substrate, thereby potentially extending the service life of the film. To increase the adhesion strength between the TiN film and the Mg alloy substrate, a Ti or Al interlayer was deposited on the Mg alloy by magnetron sputtering. Subsequently, the adhesion strengths of TiN/Ti and TiN/Al were determined under a single high shear force by scratch tests and were determined under multiple low shear forces by friction and wear tests. The results of scratch tests show that TiN with the Ti interlayer on the Mg alloy substrate has superior adhesion strength under a single high shear force. And the results of friction and wear tests show that both the TiN/Al and TiN/Ti films provided protection to the Mg alloy substrate against friction and wear, and TiN with the Ti interlayer on the Mg alloy substrate has superior adhesion strength under multiple low shear forces. This work can provide guidance for the selection of interlayers between Mg alloy substrates and hard ceramic films.
10 November 2019 in International Journal of Modern Physics B