Thermal stability of Zr-O-N(:Ti) thin films prepared by magnetron sputtering

Abstract

Metallic oxynitrides are materials of interest, since they represent the combination between the properties of the respective nitrides and oxides. The thermal stability of the oxynitride films is important for different applications, but it has to be differentiated from oxidation resistance. For this evaluation, x-ray diffraction (XRD) patterns have been acquired in situ during heating under two different atmospheres selected to avoid external oxidation (vacuum and a He/H2 mixture). Such tests were performed on selected Zr-O-N films presenting different chemical compositions and phases (metal-rich N-deficient nitride, (oxy)nitride, and O-rich disordered oxynitride). The influence of the addition of Ti has been studied in films including also TiN-like phases. To facilitate the phase identification, the intensity of the different peaks in the XRD patterns was tuned to highlight the weaker ones. In addition, the intensity of representative peaks of the main phases has been monitored to represent the overall behavior under heating. It has been found that the structure of the films evolves to the formation of ZrO2, the phase with tetragonal symmetry at lower temperature and the monoclinic one at higher temperature. Films including Ti showed an improved thermal stability, without the formation of the monoclinic oxide even at 1000 ºC.