Investigation of ZrO<inf>x</inf>/ZrC–ZrN/Zr thin-film structural evolution and their degradation using X-ray diffraction and Raman spectrometry

The thin-film structures of DC/FR magnetron-sputtered ZrOx/ZrC–ZrN/Zr tandem solar-selective coatings are investigated using X-ray diffraction and room-temperature Raman spectroscopic measurements. These studies suggest that the major contribution is coming from h-ZrN0.28, c-ZrC, h-Zr3C2 crystallographic phases in ZrN–ZrC absorber layer, in conjunction with mixed ZrOx crystallographic phases. The change in structure for thermally annealed samples has been examined and observed that cubic and hexagonal ZrOx phase converted partially into tetragonal and monoclinic ZrOx phases, whereas hexagonal and cubic ZrN phases, from absorber layer, have not been observed for these thermally treated samples in air. These studies suggest that thermal treatment may lead to the loss of ZrN phase in absorber, degrading the thermal response for the desired wavelength range in open ambient conditions in contrast to vacuum conditions.