Bilayer a-C:H/MoS2 film to realize superlubricity in open atmosphere

Although MoS2 film plays an important role in reducing friction, however, it will collapse down at higher loads. To prevent the failure of MoS2 under higher load, in present work, structure bilayer a-C:H/MoS2 films were prepared via PVD/PECVD hybrid method. The component, bonding structure, morphology as well as trichology and mechanical properties of the films were investigated, respectively. The results show that MoS2 film stack uniformly on a-C:H film's surface. Due to the special design of the structure, the bilayer a-C:H/MoS2 film show a sufficient decrease of friction coefficient compared with that of a-C:H film. In addition, the superlubricity state was achieved at very high loads, which can be ascribed to the low shear force and incommensurability contact between adjacent MoS2 layers. And a-C:H film here plays as foundation stone of supporting MoS2 film and enforcing its adhesion on silicon substrates, which inhibits slipping away of MoS2 film under shear force. Our work can open a new mind to help design the high loads capability of MoS2 based films, which can break the deadlock of the bad loading ability and achieve superlubricity at even higher loads for MoS2 based films.