Niobium zirconium nitride nanocrystalline films were deposited by DC unbalanced magnetron sputtering on silicon substrates with a growth temperature of 450 degreesC and an RF bias voltage of -70 V. The concentration of zirconium and niobium was regulated by controlling the power to the sputtering guns. The nitrogen concentration was controlled by varying the nitrogen flow rate and, hence, partial pressure. These films were investigated by means of X-ray diffraction, X-ray photoelectron spectroscopy, spectroscopic ellipsometry (SE), and nanoindentation. XRD revealed that these films formed a solid solution and that the grain size, deduced from the width of the XRD peaks using the Scherrer formula, did not vary with niobium content. The elemental composition was determined from XPS measurements. The optical constants were measured using SE and were found to correlate well with film structure and composition using a Drude-Lorentz (DL) model. The mechanical properties of the coatings were evaluated using nanohardness testing and were found to depend on composition. Optimum mechanical properties were achieved for a niobium content of 12%. (C) 2004 Elsevier B.V. All rights reserved.