Relationship between applied voltage and S/Mo ratio of molybdenum disulfide films prepared by applying various positive voltages to substrates under the sputtering condition of constant argon pressure and radio frequency (RF) power was investigated. The S/Mo ratio analyzed by EPMA increased in the range of 1.96 to 2.25 when the voltage was applied from 0 to 60 V. The S/Mo ratios measured by EPMA and those analyzed by peak separation of XPS were compared. It was confirmed that both S/Mo ratios showed good agreement with each other. Moreover, film properties such as impurity contents, density, internal stresses, crystalline orientation and interplanar spacing, which would relate to tribological performance, were clarified. Especially, Fe elements composing the substrate were detected in the films at the applied voltage of 45 V and 60 V. To confirm the status of Fe elements in the film, XPS analysis was performed. As a result, it was found that Fe elements were distributed throughout the film thickness.
It is thought that sandfish skink, living in desert, has scales that have low friction and high wear resistance properties. In previous study, we investigated the tribological properties of sandfish's scales under micro newton loads. It is found that the scales have low adhesion forces, which would lead to the low friction property. In this study, a tribological property of sandfish's scales was investigated under milli newton loads (of 3, 5, 10 mN) to investigate wear resistance property mainly. Tribological tests were also carried out using polytetrafluoroethylene (PTFE) and polyimide (PI) for comparison with the scales. Using a SUJ2 ball with a diameter of 1 mm, wear of sandfish scale was not occurred or much lower than those of PTFE and PI. When wear was not happened for sandfish's scale in the relative low contact pressure, a friction coefficient of the sandfish's scale was lower than those of PI and PTFE. When a tungsten probe with an apex diameter of 5 μm was used in which contact pressure was huge with compare to that using the SUJ2 ball, wears on all samples were observed. In the relative high contact pressure, the friction coefficient of sandfish's scale was higher than that of PI. Under the milli newton loads, the microstructure of the sandfish's scale did not affect its tribological property.