Summary

Thin films of NbSiyNx have been deposited by reactive magnetron sputtering from confocal Nb and Si targets in mixed Ar/N-2 atmosphere, at a substrate temperature of 250 degreesC. The total pressure, the nitrogen partial pressure and the current on the Nb target were kept constant, while the current on the Si target was varied in order to obtain Si concentrations between 1 and 34 at.%. For Si contents below 11 at.%, X-ray diffraction (XRD) reveals that the films are crystalline and have a fcc delta-NbN structure. For higher Si concentrations, the films exhibit a multiphase structure consisting of delta-NbN nanocrystallites and an amorphous matrix. The texture and the crystallite size depend on the Si content. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) measurements allowed to identify the amorphous phase as Si3N4. Transmission electron microscopy (TEM) observations reveal that the microstructure of films is columnar, and that each column is formed by an agglomerate of crystallites. Amorphous regions were observed on the high-resolution transmission electron microscopy (HRTEM) images of the films with C-Si = 11 and 20 at.%. Nanoindentation measurements show that the hardnes