LASER-ABLATION OF DIAMOND FILMS IN VARIOUS ATMOSPHERES

Diamond films of 5-mu m thickness are irradiated with the emission of an ArF excimer laser (193 nm, tau=20 ns, repetition rate=20 Hz) in air , O-2, He, H-2, N-2 and vacuum. The sample surface is polished with th e laser beam under an angle of incidence of 80 degrees. Atomic Force M icroscopic (AFM) measurements show differences of morphology and avera ge roughness between polished films treated in different atmospheres. In a second experiment, the ablation depth is measured at normal incid ence of the laser light. Depending on the atmosphere, different etchin g depths are measured. In He, H-2, and N-2, graphitic borders surround the ablation hole. They are assigned to sputtered ablation particles that were not combusted due to the absence of O-2. During laser ablati on in air, O-2, and in vacuum, the amount of the sputtered carbon arou nd the irradiated spots is significantly reduced, and no graphitic bor ders can be observed after irradiation. The black borders around the h ole and the surface inside the ablated area are found to contain glass y carbon structures that can be etched away in a H-2 plasma as shown w ith micro-Raman spectroscopy. (C) 1998 Elsevier Science S.A.