Structure and Emission Evolution in Si-Rich HfO2:Pr Films Versus Annealing Temperature

Abstract

Pr-doped Si-rich-HfO2 films with specific emitting and structural properties have been prepared by radio-frequency magnetron sputtering using standard pure argon plasma approach. The effect of post-deposition thermal annealing on the transformation of crystalline phases, their compositions and photoluminescence spectra was investigated by means of the Energy Dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), scanning electronic microscopy (SEM), Raman scattering and photoluminescence (PL) methods. Thermal annealing was carried out at 800 °C, 900 °C, 1000 °C and 1100 °C within time of 30 min in nitrogen atmosphere. The SEM images demonstrate the grains with the size about 40 nm. It was observed that the influence of temperature at annealing causes the phase transformation and separation processes. In studied samples, the formation of the tetragonal HfO2 and SiO2 phases, were detected at XRD study after the annealing at 1000 and 1100 °C. PL spectra of these films are complex and demonstrate several PL bands centered at 442, 479, 523, 607, 637 and 716 nm. Their contribution depends on the annealing temperature and governs the shape of total PL spectra. The impact of crystalline phase separation on the peculiarities of PL spectra and XRD are analyzed and discussed.