EFFECTS OF EXCIMER-LASER POLISHING ON SURFACE-PROPERTIES AND TRIBOLOGICAL PERFORMANCE OF DIAMOND FILMS

Diamond films of various thickness (from 2 to 10 mu m) and roughness w ere polished using a scanning beam of an ArF excimer laser (lambda = 1 93 nm), and the friction and wear characteristics of the laser-polishe d films were studied against a monocrystalline ruby ball using a pin-o n-disk tribometer. It was shown that the value of surface roughness ac hieved by laser polishing was governed by the original film roughness which increased with film thickness. The lowest roughness R-a = 10 nm was obtained for a 2-mu m-thick film. The properties of the laser-grap hitized surface were examined using Raman and Auger electron spectrosc opy techniques. Under laser irradiation with a grazing beam, the thick ness of the graphitic layer and the ability of the graphitized diamond surface to adsorb oxygen were found to depend on the number of laser shots (polishing time). The friction and wear performance of the laser -polished films was correlated with the roughness and morphology of th e films, but the role of surface graphitization on friction behaviour was not clearly established. It was supposed that the passivation of t he laser-ablated surface for oxygen/water adsorption was a limiting fa ctor for the reduction of friction during the sliding process in a hum id air environment. The tribological properties of the laser-polished diamond films were compared with those of a mechanically polished film which was also graphitized as a result of irradiation by ArF laser pu lses.