Superlubricity of Sputtered MoS₂ Film in Dry Air Enabled by Proton Irradiation

The superlubricity of sputtered MoS₂ film under dry air environment was achieved by low-energy proton irradiation of 25 keV for the first time. We found that proton (H⁺) irradiation is able to break the Mo-S covalent bonding of as-deposited MoS₂ film and leads to the formation of MoS₂ nanocrystalline domains. The dangling bonds at edge planes or newly exposed edges could be passivated with hydrogen ions by bonding interaction under proton irradiation, forming hydric MoS₂ nanocrystalline domains with stable S–H bind, resulting in superior antioxidant capacity of proton-irradiated MoS₂ film compared to its non-irradiated counterpart. Importantly, proton irradiation can penetrate the interior of sputtered MoS₂ film with thickness over 1 µm and restructure the as-deposited MoS₂ film into nanocrystalline MoS₂ domains to achieve superlubricity and life extension under dry air conditions.