IMPROVEMENT OF MECHANICAL-PROPERTIES OF AMORPHOUS-CARBON FILMS DEPOSITED ON POLYCARBONATE PLASTICS

Amorphous carbon films have been deposited on polycarbonate surfaces u sing laser ablation technique. The polycarbonate substrates were treat ed with oxygen plasma prior to him deposition. Mechanical properties o f the films were examined as a function of plasma pretreatment time. R esults showed that the mechanical behavior of the carbon film improved with pretreatment time. A one-hour pretreated sample exhibited no cra cking, good adhesion, low stress and a hardness of 5 GPa which is 20 t imes higher than that of bare polycarbonate. Spectroscopic ellipsometr y was used to characterize the film and interface properties in order to understand the effect of plasma on polycarbonate surface. Computer modeling of the ellipsometry data revealed that the improvement of mec hanical behavior of the films is due to the modifications of the polyc arbonate surfaces after the oxygen plasma treatment. Further correlati on studies of surface modification by oxygen plasma was carried out by atomic force microscopy and stress measurement. Optical emission spec tra from the plasma plume during laser ablation showed that the neutra l and ionic carbon atoms were the dominant species. We believe their p resence plays a major role in controlling the properties of our diamon dlike carbon films.