Microstructure and friction-reducing performance of sulfurized W doped diamond-like carbon film

► W-DLC film was treated by low temperature ion sulfuration. ► A soft WS2 layer about 100 nm in depth is formed on W-DLC film. ► A slight increase of sp2-C content in the DLC film is contributed to sulfuration. ► Sulfuration reduces the friction coefficient of W-DLC film.