Erosion Mechanism of MoS2-Based Films Exposed to Atomic Oxygen Environments.

The erosion mechanism of magnetron sputtered MoS2 films exposed to the atomic oxygen environment was studied and compared with the Ti-doped MoS2 and MoS2/Ti multilayer films. The compositional and structural changes were investigated as a function of incident fluence by Rutherford back scattering (RBS) and focused ion beam combining with scanning electron microscopy (FIB&SEM). The RBS results indicate that the sulfur atoms are eroded by the incident atomic oxygen atoms and the removed sulfur amount increases but the erosion rate decreases with increasing of incident fluence. For pure MoS2 films the erosion process turns to saturate at the end of investigated fluence of 4.8×10(21) O cm(-2), and for Ti-doped and MoS2/Ti multilayer films the saturation of sulfur erosion is much earlier around incident fluence of 5.2×10(19) and 2.6×10(19) O cm(-2), respectively. FIB cross-section results reveal that pores structures present in the as-deposited MoS2 films provide a reaction highway, which allows the incident atomic oxygen to be able to reach and react with the sulfur at bottom. Introducing titanium doping or MoS2/Ti multilayer structures definitely reduce the density of pores and defects in the initial films, consequently, erosion process is suppressed or blocked, and the instinct lubricant properties of MoS2 phases can be well-retained in vacuum sliding conditions.