A new “cyclic” r.f. plasma method for the deposition of diamond-like carbon films

Abstract

Inspired by the now widely used “double-beam method” for ion beam deposition of diamond-like carbon (DLC) films, we have explored a new method to produce DLC films using an r.f. plasma system with a water-cooled substrate holder. The films are formed using several repeated deposition and treatment cycles: (1) a high flux of hydrogen is first introduced to the system and some is absorbed at the surface on which the film is to be grown; (2) the hydrocarbon gas (CH 4) is then introduced and undergoes ionization and dissociation in the r.f. field to deposit the film; followed by (3) bombardment of the deposited film in an argon plasma. This cycle is repeated several times, and the film produced is characterized by optical spectroscopy and Vickers hardness number (VHN) measurements. The results indicate that hydrogen pre-absorption has some effects on film structure and properties. The number of sp 2 bonded carbon atoms is reduced although hydrogen content in the film only increases slightly. The argon bombardment removes weakly bonded atoms from the film and increases film hardness. In addition the deposited films have reduced internal stresses. In the present paper, influences of cycle parameters are discussed in terms of film properties.