Structural stability of decorative ZrNxOy thin films

Abstract

ZrNxOy thin films were prepared by rf reactive magnetron sputtering. The thermal stability of the coatings was tested in vacuum for an annealing time of 1 h in the temperature range 400-800 °C. Residual stresses originated by the deposition process were partially or almost completely released with the annealing, which is consistent with the X-ray diffraction results. Samples with low oxygen fraction (0.10 < fO2 < 0.22) showed no significant changes in hardness after thermal annealing at 800 °C. For intermediate and high oxygen fractions, an initial decrease in hardness at 600 °C annealing is followed by an inversion at the highest temperatures (700 and 800 °C, respectively), resulting from possible oxide phases crystallization, defect annealing at high temperatures and some extended phase segregations. The increase in the oxygen fraction is followed by a decrease of hardness in the as-deposited samples towards the values of "pure" ZrO2. No significant changes in colour were observed with the annealing.