Surface and bulk properties of electron beam evaporated carbon films

Amorphous carbon films deposited by electron beam evaporation onto glass and oxidized Si(111) substrates have been investigated by local probe methods, spectroscopic techniques and electrical measurements. Clusters similar to 15 Angstrom in diameter are visible in the topography imaged by scanning tunneling microscopy. The microscopic potential distribution mapped by scanning tunneling potentiometry is characterized by a disturbed lateral potential drop in the submicrometer scale. X-ray diffraction analysis reveals the amorphous structure of the evaporated film. In the Raman spectrum two broad lines at 1585 cm(-1) and al 1375 cm(-1) are observed. We obtained an optical absorption coefficient alpha greater than 10(5) cm(-1), and a small optical gap of about 0.2 eV. The electrical resistance at low temperatures can be fitted to the form R proportional to exp(T-0/T)(1/2). Our experimental results indicate a structure consisting of very small graphite (sp(2)) clusters with an incomplete trigonally atomic arrangement. The changed bonding configuration between the clusters may include sp(3) sites.