Preparation and properties of COx films

New types of amorphous graphite-like COx films were obtained by two ways: (i) magnetron sputtering of a graphite target in the gas mixture Ar+O2; and (ii) air annealing at 250–300 °C of a-C films deposited by magnetron sputtering in Ar. These films contain at most 18–22% atomic oxygen, depending on the way of preparation. They remain stable in air and vacuum up to 300 °C. The transition from graphite-like a-C to a-CO0.2 is accompanied by a sharp increase in electrical resistivity and IR transmittance. Two characteristic absorption bands at approximately 1700 and 1605 cm-1 appear and the G band in the Raman spectrum shifts to approximately 1605 cm-1. Electron diffraction reveals that only those films with 002 interlayer distance increased with respect to that of graphite may be saturated with oxygen up to approximately 22 at. %, until they become strongly vaporized.