Physical and mechanical properties of chromium zirconium nitride thin films

This paper reports on the physical, chemical, mechanical, and tribological properties of reactively sputtered chromium zirconium nitride deposited on Si (111) substrates using Cr and Zr targets. These films were grown using a fixed power to the Zr target (70 W), a fixed flow of nitrogen (1.5 sccm), but with a variable power to the Cr target (0–13 W). The chemical composition was deduced from X-ray photoelectron spectroscopy measurements. X-ray diffraction revealed that a two-phase nanocomposite material was formed when the power to the Cr target exceeded 3 W. The nanocomposite consisted of nanocrystals of (Cr, Zr)N, 5–7 nm in size, embedded in an amorphous matrix. The optical constants were measured using spectroscopic ellipsometry and were simulated using a Drude-Lorentz model. This model revealed that the density of free electrons increased with the increase in the power to the Cr target while the resistivity decreased because of the increased grain boundary scattering due to the formation of a nanocomposite structure. The hardness and elastic modulus values were measured by nanoindentation and were correlated to the microstructure of the films. Microwear measurements were carried out using positive constant normal loads and the wear tracks were imaged and processed using the ProScan Image Processing software. The values for the residual depth of tip indentations and wear volumes were reported for the various film compositions.