An investigation of the electronic and structural properties of pulsed laser-deposited a-C films

The electronic and structural properties of amorphous carbon films have been studied by means of Raman and X-ray photoelectron spectroscopy. The films were deposited, under vacuum, by KrF excimer laser ablation of graphite targets. Both the substrate temperature and laser fluence were increased up to 900 K and 15 J cm-2, respectively. The Raman spectra of the films deposited at room temperature showed the presence of a broad band peaked at nearly 1550 cm-1 with a shoulder in the 1300-1400 cm-1 region, with an sp3 content ranging from 60 to 70%. Upon varying the laser fluence, only slight modifications in the Raman spectra were observed. On the contrary, increasing the substrate temperature increased the low-frequency component, suggesting an increase in the sp2 content. This result is also supported by the lineshape modifications observed for the C 1s photoemission peak and by a possible reduction in the film density.