Hydrogen incorporation and its structural effect on a-C:H films deposited by magnetron sputtering

Films of a-C:H have been prepared by dc magnetron sputtering from a graphite target with various ratios R of flow rates, or pressures, of H to Ar plus H in the chamber. In the analysis of the infrared (IR) spectra of a set of films with R varying from 2.5 × 10−5 to 0.9, features characteristic of vibrational modes associated with H bonded in a variety of configurations, namely sp2 and sp3 sites involving single-, double- or (in the case of sp3 sites) triple-bonded H, are detected. The relative fractions of the different sites do not change with R up to about 0.1 but, for larger R, the fraction of sp3C sites bonded to a single H atom increases and the other configurations decrease. At the same time the linewidths of the peaks contributing to the overall spectra increase with R, which we suggest is due to increased stress in the films.