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

• Published in: Diamond and related materials 2002-03, Vol.11 (3-6), p.980-984
• Main Authors: Lacerda, R.G., Stolojan, V., Cox, D.C., Silva, S.R.P., Marques, F.C.
• Format: Article
• Language: English
• Subjects: Chemical vapor deposition (including plasma-enhanced cvd, mocvd, etc.); Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Diamond-like carbon; Exact sciences and technology; Hardness; Materials science; Mechanical and acoustical properties; Mechanical properties; Methods of deposition of films and coatings; film growth and epitaxy; Physical properties of thin films, nonelectronic; Physics; Stress; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties)
• ISSN: 0925-9635; 1879-0062
• DOI: 10.1016/S0925-9635(01)00677-X

Hard a-C:H films have been deposited at an industrially significant growth rate (∼0.7 nm/s), with high hardness (∼19 GPa) and relatively low stress (∼1.3 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 (∼12 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% sp2 sites, yet maintaining a relatively high hardness. It is thought that the sp2 sites contribute to the film hardness, together with the remaining sp3 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 μm) suitable for application such as protective coatings.