Effect of deposition and anneal temperature on the resistivity of magnetron sputtered carbon films

Amorphous carbon (a-C) films were deposited by d.c. magnetron sputtering of a graphite target in an argon plasma. The dependence of film resistivity on deposition and anneal temperatures has been studied in the range 20–650 °C. The film structure was examined by Raman spectroscopy and reflective high-energy electron diffraction (RHEED). Films revealed prominent resistivity anisotropy, the degree of which depends on temperature. The change in substrate temperature during deposition affects more strongly the degree of resistivity anisotropy in a-C films than in the case of post-deposition annealing. The results obtained suggest that film structure is formed by predominantly sp2-bonded carbon atoms. In the range of deposition temperatures 20–400 °C, ordered regular aromatic rings and graphite-like clusters form, and the extent of ordering increases with the increase in deposition temperature. In the range 450–650 °C the growth mechanism changes and the nuclei of graphite phase form and grow directly on the substrate. Annealing of a-C films in the range 50–300 °C results in intense transformation of distorted aromatic rings into regular ones, and also in ordering of them in the substrate plane without formation of graphite fragments. Further increase in the anneal temperature up to 650 °C has little influence on the structure of the film.