Constructing WS2/MoS2 nano-scale multilayer film and understanding its positive response to space environment

Characteristic porous microstructure causes poor wear resistances of sputtered transition metal dichalcogenides (TMDs) films that have important applications in space technology. TMDs/metal multilayer films exhibit improved microstructural and tribological properties, but which are unreliable due to the mismatch in thermal/mechanical properties between them as well as the metal sensibility to atomic oxygen (AO). In this study, MoS2/WS2 nano-scale multilayer films were fabricated to improve the microstructural, mechanical, tribological and environment-adaptive properties of TMDs films. Results revealed that as compared with MoS2 or WS2 single layer film, the multilayer film exhibited a dense microstructure, strong (002) texture and high hardness. Correspondingly, it showed a significantly improved wear resistance in vacuum, whose wear life was similar to one order longer than those of single-layer films. Simulation tests revealed that even drastic thermal shock could not cause the delamination of multilayer film, which was observed from TMDs/metal multilayer system; and the oxidation from AO irradiation was restricted into film surface layer (<= 10 nm). These results indicated that the micro structural, mechanical and tribological properties of TMDs films were significantly improved by the nano-scale multilayer design, and the fabricated multilayer film had potential applications in space technology.