Electron-irradiation damage in chromium nitrides and chromium oxynitride thin films

The aim of this work is to monitor changes of the N-K electron energy-loss near-edge structure (ELNES) of chromium nitride layers (CrN) introduced by electron irradiation in a transmission electron microscope (TEM). These changes are different for each sample material and seem to give an indication for a particular composition. The CrN samples (CrN and Cr0.47N0.53) were prepared on silicon wafers by reactive magnetron sputtering of a metallic chromium target in nitrogen plasma. In addition, a CrON sample (Cr0.5O0.2N0.3) was also investigated. This sample was prepared by the addition of oxygen to the plasma during film deposition. The ELNES of the N-K ionization edge of stoichiometric CrN shows a typical fine structure (peaks at 399.0 and 401.1 eV) and remains nearly unaffected even after high-current-density irradiation. On the other hand the N-K fine structures of Cr0.47N0.53 and Cr0.5O0.2N0.3 show a change of the ELNES with irradiation dose. This presumably arises from a 1s-π*-transition of molecular nitrogen located at interstitial positions in these samples.