Thermally-induced optical property changes of sputtered PdOx films

Optical property changes of reactively sputtered palladium oxide (PdOx) thin films during heating have been investigated by light transmission measurements and in situ Raman spectroscopy, combined with X-ray fluorescence and thermogravimetry analysis (TGA). The composition ratio and refractive index of as-deposited PdOx films varies depending on the oxygen gas-flow ratio during sputtering deposition. The transmitted light intensity at wavelengths of 405 and 635 nm measured during heating up to 1000 °C in air exhibits a sharp leap at 832 °C due to the thermal decomposition of PdO, and shows a gradual increase around 200-300 °C. The decomposition process of PdO is also measured by TGA as a significant weight loss of the sample. In situ Raman spectra of sputtered PdOx film obtained during heating up to 600 °C in air demonstrate that the crystallization of PdO starts above 200 °C and progresses during the whole annealing process.