Photoluminescence properties of CaWO4 and CdWO4 thin films deposited on SiO2/Si substrates

In this study, we present photoluminescence (PL) analyses under UV and X-ray excitations of thin layers of CaWO4 and CdWO4 deposited on SiO2/Si substrates, by radio-frequency sputtering method. The main objective was to determine the efficiency of PL emissions in the case of these specific SiO2/Si substrates. Polycrystalline CaWO4 and CdWO4 phases were used as standards for PL emission analyses. Characterizations of films were carried out by X-ray diffraction, scanning electron microscopy, and atomic force microscopy. The PL experiments were carried out under monochromatic UV and polychromatic X-ray excitations. The PL intensities varied with tungstate film thicknesses. In the case of X-ray excitation, oscillations of PL intensities were observed. These oscillations corresponded to interferences of PL emissions, strongly correlated with the thickness of intermediate SiO2 layers. A Fabry-Perot model simulating these oscillations is applied allowing differentiating the PL responses of these films.