Low energy Auger electron spectroscopy of vanadium nitrides

The low energy (20–40 eV) region of the Auger spectrum of vanadium nitrides has been studied in order to extend and complement earlier investigations of titanium nitride. The method of using the high-energy spectrum as an internal calibration has also been used in this work which is made easier by the absence of peak overlap between the nitrogen and metal peaks. The background subtraction and peak deconvolution techniques have been considerably extended in this paper. Two methods have been used for representing the background in the derivative spectrum. In the first approach the smooth part of the background has been fitted using the derivative of a Gaussian as the fitting function. After integration of the background subtracted spectrum, the step caused by inelastic scattering was removed by the “Shirley step” removal procedure. In the second method we used the stoichiometric nitride spectrum to represent the background for all VNx samples with x < 1. The different methods were in excellent agreement, strengthening our confidence in the results. The resultant spectra clearly contained two peaks, a large “metal” and a much smaller “nitride” feature, which were deconvoluted using the pure metal peak shape for fitting both peaks. As was the case with TiNx, the intensity of the “metal” V(3p)V(3d)V(3d) peak was linear in x, i.e. the number of unoccupied octahedral holes, whereas the “nitride” V(3p)V(3d)N(2p) cross transition was a maximum for x = 0.5, again correlating with the number of adjacent occupied-unoccupied holes in the nitride structure.