Interaction of oxygen with a-C:H, a-C films and other carbon materials

Magnetron sputtered films of a-C:H, a-C, as well as of a-COx, and glassy carbon and graphite were annealed in air and vacuum at different temperatures (up to 770 degreesC). The a-COx films (new type of amorphous graphite-like films) contain at most 18-22% of atomic oxygen depending on the way of their preparation. Annealing in air results in the removal of H from a-C:H films and in the incorporation of 0 in both a-C:H and a-C films as evidenced by IR spectra. Raman spectra show the up-shift of the G band (to approx. 1605 cm(-1)) in a-C and a-C:H films. Annealing of a-COx films at 770 degreesC in vacuum shifts the G band down to similar to 1595 cm(-1) and decreases oxygen content sharply down to 5 at.%. Annealing of graphite and glassy carbon in air at 600 degreesC does not change their Raman spectra. The electron diffraction patterns for the a-COx films are almost the same as for the a-C films, implying that oxygen occupies mainly the positions along the edges of graphite layers in every cluster and acts as an etchant. Its action decreases the intrinsic stress and leads to short-range order increase. (C) 2003 Elsevier B.V. All rights reserved.