PECULIARITIES OF NEAR-RANGE AND MEDIUM-RANGE ORDER IN A-C-H FILMS EXHIBITING A PHOTOINDUCTION EFFECT

The results of a detailed investigation of the composition and structu re of a-C:H films, in which a UV-stimulated change in the optical prop erties is observed, are reported. The a-C:H films were prepared by two methods: magnetron sputtering of a graphite target in a mixture of ga ses Ar+H and high-frequency decomposition of CH+Ar. Infrared spectrosc opy showed that, depending on the conditions under which the films are prepared, the films are characterized by a predominant mono- or dihyd ride form of the hydrogen-carbon bond. The hydrogen concentration depe nds on the technological conditions and ranges from 10 to 20 at. %. It is shown that UV irradiation does not change the initial hydrogen con centration. The oxygen concentration in the a-C:H films before and aft er UV irradiation was determined by the method of resonance nuclear re actions. It is shown that the oxygen concentration in the irradiated s amples is 1.5 times higher than in the unirradiated samples. The role of oxygen in the photostructural transformations is discussed. (C) 199 6 American Institute of Physics.