THE INFLUENCE OF THE ION-BOMBARDMENT ON THE OPTICAL-PROPERTIES OF TINX AND ZRNX COATINGS

The aim of this work was to investigate the inter-relationships betwee n the ion bombardment during film growth, the resulting chemical compo sition and microstructure and the optical properties of TiNx and ZrNx coatings. Samples were prepared by non-reactive d.c. unbalanced magnet ron sputtering from TiN and ZrN targets. The energy and intensity of t he argon ions impinging on the film surface was varied systematically using different bias voltages and different external magnetic fields a pplied via a Helmholtz coil system. Coatings were characterized using wave-length dispersive electron-probe microanalysis, X-ray diffraction , spectroscopic ellipsometry and CIE-La*b* colorimetry. For a brillia nt appearance the formation of coatings with a well-defined crystal la ttice and a chemical composition close to stoichiometry was found to b e necessary. The metallic character of ZrN coatings characterized by t he plasma frequency seems to be more pronounced than for TiN-based fil ms. Varying ion bombardment conditions resulted in TiNx coatings with different chemical compositions (x ranging from 0.85 to 1.02). Thus, a lso their optical properties were determined by their chemical composi tion. For ZrN, coatings, the lattice parameter was affected by the ion bombardment for given values for the ion intensity, giving rise to a close relationship to the coloration. (C) 1998 Elsevier Science S.A. A ll rights reserved.