Spectroscopic Characterization of Hard Carbon and Carbon-Based Films

There is a considerable interest in hard carbon films, with useful mechanical properties like hardness, elasticity and low friction coefficient. The wide diversity of the carbon forms makes growth and characterization of diamond-like carbon (DLC) and related materials complicated. Electron spectroscopy constitutes a powerful tool to investigate the surface composition and species, the chemical bonding and the surface electronic states. In this work, X-ray photoelectron spectroscopy was applied to study the electronic and chemical structure of (i) pure carbon films and (ii) carbon-based material films, r. f. sputter-deposited on various substrates (Si, cemented-WC and plastics). The diamond-like features of the electronic valence band (strong s-p-orbital mixing) were correlated with the rigidity of the carbon network, found to be comparable to that of diamond. Low friction nitrogen-containing carbon films (CNx), with a high network rigidity index, and composites as Ni-DLC films, characterized by diamond-like mechanical properties (hardness and elasticity), were synthesized and electron spectroscopy was very useful in determining their chemical structure and composition. Furthermore, efforts are being made to develop in-situ diagnostics in order to characterize the growing films, and to avoid any aging effect, whatever spontaneous or environmental, from which the ex-situ diagnostics are not totally immune