Correlation Between Stoichiometry of NbxNy Coatings Produced by DC Magnetron Sputtering with Electrical Conductivity and the Hall Coefficient

Non-stoichiometric NbxNy coatings, produced in a reactive sputtering process, were analyzed on the basis of their chemical composition (specifically, nitrogen concentration) and its relationship with electrical conductivity. The chemical composition and bonding configuration were examined using X-ray photoelectron spectroscopy (XPS), revealing Nb-N bonds. The stoichiometry variation dependence on the N-2 flow was also analyzed, using Auger electron spectroscopy (AES). Without exposing the samples to air, a normal behavior was observed; meaning that the nitrogen concentration in the coatings increased, with an increase in N-2 flow. The electrical properties were evaluated and their relationship with nitrogen content in the films was analyzed. The highest conductivity value for all studied samples was observed for the sub-stoichiometric film, NbN0.32, which also exhibited a positive Hall coefficient. It indicated that the conduction was mainly dominated by hole-type carriers. High conductivity at lower nitrogen content was attributed to the fact that, at a low concentration of nitrogen, the effect of impurities, acting as dispersion points for electrons, was lower, increasing the relaxation time. As the main conclusion, the Ar/N-2 flow ratio strongly influenced the coatings of stoichiometry and then, this stoichiometry affected, to a great extent, the electrical conduction and the Hall coefficient of the coatings.