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

Highly oriented pyrolytic graphite HOPG.was irradiated by an ArF excimer ls193 nm.laser above the ablation threshold, at approx. 0.45 and 2 Jrcm2. The surface morphology and the quality of the remaining material was investigated by atomic force microscopy AFM.and area-selective Raman spectroscopy. At the lower fluence a material removal rate of several monolayers per laser pulse was detected, without changing the quality of the remaining material. Irradiation at the higher fluence resulted in ablation rates of the order of 10 nmrpulse and the formation of an approx. 300 nm thick diamond-like carbon DLC.film with approx. 50% concentration of the sp3 hybrid-states of carbon. In the surroundings of the ablated hole a narrow ring of mechanically soft, nanocrystalline and turbostratic carbon was observed. Upon annealing the irradiated surfaces in air at 6508C for 30 min, the graphite structure of the laser-modified layer was perfectly recovered with the disappearance of the surrounding ring. q1999 Elsevier Science B.V. All rights reserved.