Laser and thermal induced micro-structural changes and decompositionof hydrogenated carbon films

Abstract

Micro-structural changes and decomposition of hydrogenated carbon films onmagnetic disk substrates prepared by DC-magnetron sputtering were studiedusing Ar+ laser irradiation and physical heating in air and nitrogenambience, respectively. It was found that a weak Ar+ laser of a fluenceof 0.3 mW µ m-2 could significantly decompose a-C:Hfilms. The decomposition rate was fast initially and slowed downsignificantly after about 20 min. The decomposition rate of a-C:H increasedwith hydrogen concentration in the film. Raman light intensities of theirradiated sites reduced exponentially with irradiation time. Physicalheating in air revealed that the oxidation-dominated decomposition tookplace between 320 and 350 °C within 15 min, and an increased hydrogenconcentration made the a-C:H film more vulnerable to decomposition. At150-300 °C, a phenomenon of nano-crystal graphite formation was observed fromRaman spectra. XPS analysis indicated that there was no significantdiffusion of carbon atoms into the substrate at 400 °C heating.