Abstract: A process for depositing amorphous or nanophase diamondlike carbon (DLC) and a-C:H carbon/hydrogen films with variable and controllable properties on the surface of a substrate is disclosed. The process utilizes a combined hydrocarbon ion beam and plasma-activated hydrocarbon gaseous radical flux produced by an end-Hall ion source to yield a film with good electron-emissivity characteristics or high hardness and good optical transparency, as desired. A second ion source providing a beam of argon ions above or together in nitrogen is optionally directed at the substrate for cleaning prior to deposition and for ion-assisted deposition during deposition or for doping.