Structural properties of carbon films deposited by pulsed ArF laser ablation: effects of substrate temperature, bias and H2 pressure

The structural properties of carbon films grown at different conditions using ArF pulsed laser deposition are reported. Diamond-like carbon (DLC) films were grown by laser ablation of graphite in a H2 atmosphere and a substrate temperature range of 30–500°C with a substrate bias range of +200 to −500 V. The structural properties, crystallinity and morphology of these DLC films were investigated by means of RHEED, Raman and atomic force microscopy (AFM) spectroscopies, and spectroscopic ellipsometry. The films deposited under optimal conditions contained nano-size diamond crystals with a lonsdaleite structure and amorphous carbon. AFM indicated that the surface morphology was considerably influenced by the H2 pressure, the substrate temperature and the substrate bias. The size of the carbon clusters was reduced and the film uniformity was improved by the applications of the substrate bias. These results suggested that the substrate bias enhanced the surface mobility of the adspecies due to the high kinetic energy of the ionic carbon species. It was also found that the formation of the diamond phase was not significantly enhanced by varying the deposition conditions except for the substrate temperature. The optical constants and band gap of these films are also discussed in terms of the deposition conditions.