Structural characterization of hard a-C:H films as a function of the methane pressure

Hard a-C:H films have been deposited at an industrially significant growth rate (similar to0.7 nm/s), with high hardness (similar to19 GPa) and relatively low stress (similar to1.3 GPa.). The films were obtained by the decomposition of methane in a r.f. environment at unusually conditions of high bias (-800 V) and high pressure (similar to12 Pa). The properties of the films were determined using optical transmission spectroscopy, electron energy loss spectroscopy (EELS), Raman spectroscopy, nanohardness, and stress measurements. The structural analysis indicates that the material is composed of approximately 58% sp(2) sites, yet maintaining a relatively high hardness. It is thought that the sp(2) sites contribute to the film hardness. together with the remaining sp(3) C-C sites. The main advantage of the films reported is the very high deposition rate coupled with the relatively low stress, which enables the growth of very thick films (>2 mum) suitable for application such as protective coatings. (C) 2002 Elsevier Science B.V. All rights reserved.