Excimer laser irradiation induced formation of diamond-like carbon layer on graphite

Highly oriented pyrolytic graphite (HOPG) was irradiated by an ArF excimer( lambda = 193 nm) laser above the ablation threshold, at approx. 0.45 and 2 J/cm(2). The surface morphology and the quality of the remaining material w as investigated by atomic force microscopy (Arn?) and area-selective Raman spectroscopy. At the lower fluence a material removal rate of several monol ayers per laser pulse was detected, without changing the quality of the rem aining material. Irradiation at the higher fluence resulted in ablation rat es of the order of 10 nm/pulse and the formation of an approx. 300 nm thick diamond-like carbon (DLC) film with approx. 50% concentration of the sp(3) hybrid-states of carbon. In the surroundings of the ablated hole a narrow ring of mechanically soft, nanocrystalline and turbostratic carbon was obse rved. Upon annealing the irradiated surfaces in air at 650 degrees C for 30 min, the graphite structure of the laser-modified layer was perfectly reco vered with the disappearance of the surrounding ring. (C) 1999 Elsevier Sci ence B.V. All rights reserved.