Amorphous hydrogenated carbon films

The structure of a-C H films may be thus pictured as sp--carbon atoms in condensed aromatic clusters, dispersed in an sp- -rich matrix, which confers to the network its characteristic rigidity. This situation can also be regarded as a random covalent network in which the sp clusters of a defined size take part in the structure as an individual composed atom with its corresponding coordination number [17]. Such kinds of models have been successfully used to describe the dependence of a-C H film mechanical properties on composition, hybridization, and sp clustering [23]. 

It is well known that the stable crystalline form of carbon at ambient conditions is graphite, which is fully sp hybidized. The synthesis of the fully sp -hybridized crystalline diamond is performed at high temperatures and pressures. So, the production of metastable carbon solids with a high fraction of sp -hybridized 

The reactions taking place at the growing surface of plasma-deposited a-C H were reviewed by Jacob [29], and from this discussion emerged a framework to understand the a-C H film deposition mechanism. This framework is to some extent equivalent to the subplantation model, since it emphasizes the role of energetic molecular ions. In addition, it takes into account the role of neutral radicals. 

Schematic of a-C H plasma deposition by radio-frequency glow-discharge (RFPECVD). 

Variation of the averaged in time electric potential across the interelectrode space. 

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Koidl, R, Wild, Ch., Dischler, B., Wagner, J., and Ramsteiner, M., Plasma Deposition, Properties and Structure of Amorphous Hydrogenated Carbon Films, Mater. Sci. Forum, Vol. 

A.A. Haasz, S. Chiu, J.E. Pierre, Y.I. Gudimenko, Thermo-oxidative erosion of amorphous hydrogenated carbon films, J. Vac. Sci. Technol. A 14 (1996) 184-191... 

P. Koidl, P. Oelhafen Amorphous hydrogenated carbon films. In E-MRS Symp. Proc. Vol. XVII Les Editions des Physique, Les Ulis 1987... 

A. von Keudell, C. Hopf, T. Schwarz-Selinger, W. Jacob Surface loss probabilities of hydrocarbon radicals on amorphous hydrogenated carbon film surfaces Consequences for the formation of re-deposited layers in fusion experiments. Nuclear Fusion 39, 1451 (1999)... 

E. Vietzke, K. Flaskamp, V. Phillips, G. Esser, P. Wienhold, J. Winter Chemical erosion of amorphous hydrogenated carbon films by atomic and energetic hydrogen. J. Nucl. Mater. 145-147, 443 (1987)... 

J. Pillath, J. Winter, F. Waelbroek. In P. Koidl and P. Oelhafen (eds.) Amorphous Hydrogenated Carbon Films E-MRS Symposia, Proc., Vol. XVII (Les Editions de Physique, Les Ulis, France 1987) p. 449... 

Kroesen, G.M.W. Schram, D.C. van de Sande, M.J.F. Fast deposition of amorphous hydrogenated carbon films using a supersonically expanding arc plasma. Plasma Chem. Plasma Process. 1990, 10, 49. 

Graphite is probably the most widely used lamellar solid lubricant. Unlike M0S2, graphite has a lower friction and lower wear in the presence of moisture than in vacuum. Therefore, graphite is not recommended for vacuum or high-temperature applications. But another form of carbon, amorphous hydrogenated carbon films (also called diamond-like carbon), has the reverse behavior It works extremely well in vacuum, but its friction coefficient is increased by the presence of moisture [37]. 

K. Miyoshi. Tribological Studies of Amorphous Hydrogenated Carbon Films in a Vacuum, Spacelike Environment. In Y. Tzeng, M. Yoshikawa, M. Murakawa, and A. Feldman, editors. Applications of Diamond Films and Related Materials. Materials Science Monographs, Volume 73. Elsevier, New York, 1991, p. 699. 

Schroeder A, Francz G, Bruinink A, Hauert R, Mayer J, Wintermantel E (2000) Titanium Containing Amorphous Hydrogenated Carbon Films (a-C H/Ti) Surface Analysis and... 

Dischler, B., in Amorphous Hydrogenated Carbon Films (P. Kodil and P. Oelhafen, eds.). Proceedings of the European Materials Research Society, Vol. 17, Editions de Physique, Paris, 1987, p. 189. 

Studies of amorphous hydrogenated carbon films and diamond films, using CRAMPS, spin-lattice relaxation measurements, etc. Measurements on hydrogen-fuUerene complexes, using various advanced solid-state NMR methods and spin-lattice relaxation studies... 

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