A method for depositing a hydrogenated diamond-like carbon (H-DLC) film on a surface of a substrate. The method includes maintaining a reduced-pressure environment around a substrate holder for holding a substrate, holding the substrate securely within the reduced-pressure environment, and forming a gas cluster ion beam (GCIB) from a pressurized gas containing hydrocarbon gas and a carrier gas. The method further includes accelerating the GCIB to the reduced-pressure environment, irradiating the accelerated GCIB onto at least a portion of the surface of the substrate, and forming an H-DLC film on the surface.