Two mechanisms of diamond phase formation during magnetron sputter deposition of amorphous carbon films

Abstract

The diamond phase formation mechanisms are analysed by a new phenomenological model of deposition of diamond-like carbon (DLC) films on Si(001) substrate. Experimental observations that make base for this model are reviewed briefly. Only the main processes, such as adsorption of carbon atoms on the surface, formation of SiC, diamond, and graphite sites, are assumed to take place. Compressive stress, induced by ion subplantation, is regarded as a main factor causing the transformation of graphite to diamond. Relationship between stress and ion energy is given by Davis’ formula. According to this model, dependences of film deposition rate versus time and dependences of film composition versus film thickness are calculated that are in agreement with experimental ones. Also, the ratio of sp/sp volume fractions as a function of substrate bias voltage was calculated. Modelling of experimental curves show that under conditions of sputter deposition of DLC films there are at least two diamond phase formation mechanisms: (i) on the surface during carbon adsorption, and (ii) in the bulk of film by subplantation induced graphite transition to lonsdaleite (hexagonal diamond).