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 the laser beam under an angle of incidence of 80 degrees. Atomic Force Microscopic (AFM) measurements show differences of morphology and average roughness between polished films treated in different atmospheres. In a second experiment, the ablation depth is measured at normal incidence of the laser light. Depending on the atmosphere, different etching 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 ablation in air, O-2, and in vacuum, the amount of the sputtered carbon around the irradiated spots is significantly reduced, and no graphitic borders can be observed after irradiation. The black borders around the hole and the surface inside the ablated area are found to contain glassy carbon structures that can be etched away in a H-2 plasma as shown with micro-Raman spectroscopy. (C) 1998 Elsevier Science S.A.