Formation of carbon-based superhard materials by condensation of evaporated carbon under rare gas or nitrogen ion irradiation

The state-of-the-art of ion-beam-assisted deposition of carbon-based superhard films, by electron-beam evaporation of carbon under concurrent bombardment with energetic rare gas or nitrogen ions from an ion source, is reviewed. These materials are hydrogenated and non-hydrogenated diamond-like carbon and nitrogen-containing carbon. Features such as the microhardness, density and porosity and experimental results on the mechanical and chemical behaviour, e.g. wear and corrosion performance, are discussed as a function of the deposition process parameters. Different mechanisms of formation of diamond-like structures are described. The controversial results on the formation of nitrogen-containing carbon phases are critically discussed. Possible explanations of parameters and mechanisms which have not been considered previously and suggestions for further experiments are given.