Carbon Thin Films Prepared by Pulsed Laser Deposition

Abstract

Amorphous carbon thin films, which do not have optical band gap, and diamond like carbon films, which do have an optical band gap, were grown by pulsed laser deposition at different laser wavelengths (λ=193nm, 532nm and 1064nm) and substrate temperatures (from room temperature to 500°C). The optical absorption spectra were measured using the spectrophotometer. Diamond like carbon films are obtained at short laser wavelength and low substrate temperature. On the other hand, amorphous carbon films were obtained at long laser wavelength and high substrate temperature. The optical band gap decreases with the substrate temperature. The morphology of the film surface was observed using an atomic force microscope. From this result, the film growth at the different laser wavelengths could be explained qualitatively to be surface growth, subsurface growth accompanied with the migration of the penetrated species to the film surface, and subsurface growth respectively using the subplantation model. This model could explain well the results of the optical band gap, the microstructure and the emission spectroscopy. All films showed the occasional incorporation of spherical particles with a diameter of 1-10μm ejected from the targets due to surface being melted.