Compositional effects on the structural, mechanical, and electrical properties of Cr–Nb–N thin films

This study reports the structural, morphological, mechanical, and electrical properties of Cr-Nb-N films deposited on MgO (001) and c-plane sapphire substrates by dc magnetron sputtering. The films were characterized by X-ray diffraction, scanning electron microscopy, nanoindentation, and electrical resistivity measurements. High-quality epitaxial Cr and CrN films were obtained, and the effects of Nb and N incorporation were systematically analyzed. Cr films on MgO remained epitaxial with increased hardness and electric resistivity when the Nb content was increased to 12%, while a high Nb content (40 at%) resulted in a nanocrystalline film. Adding nitrogen to such nanocrystalline Cr–Nb alloys yielded a phase mixture of metallic and ternary nitrides, which enhanced the hardness up to 26 GPa and resulted in a large variation in the electrical behavior. Additions of Nb into epitaxial CrN resulted in a linear lattice expansion while decreasing the electrical resistivity of CrN by two orders of magnitude. These findings demonstrate that precise control of Nb and nitrogen enables tunable structural, mechanical, and electrical properties in Cr-Nb-N films.