Excitation varying of Pr3+ ion emission stimulated by annealing in Si-rich HfO2:Pr films prepared by magnetron sputtering

The impact of high temperature annealing at 800–1100 °C on photoluminescence (PL) via 4f shell levels of Pr³⁺ions, as well as peculiarities of their excitation in Si-rich HfO₂:Pr films prepared by magnetron spattering are studied. Efficient oxidation and crystallization of Si-HfO₂:Pr films with the appearance of tetragonal HfO₂ crystalline phase after annealing at 1000 °C are revealed, which are accompanied by the increase of oxygen content in the films and dissolution of Si quantum dot (QD) inclusions. Simultaneously, efficient PL emissions connected with optical transitions in the 4f energy levels of Pr³⁺ions are detected. It has been shown that in highly oxidized films annealed at 1000 °C, the PL excitation of low energy PL bands in the 4f shell of Pr³⁺ions dominates. The latter is due to the involvement in the excitation of Pr³⁺ion emission of oxygen related defects (interstitial O_i atoms and molecules). On the contrary, upon annealing at 1100 °C, the content of oxygen atoms in the films decreases together with the generation of oxygen vacancies. This latter conclusion was confirmed by the analysis of the variable signals of Si2p, Hf4f, O1s and Pr3d in the high-resolution X-ray photoelectron spectra (HR-XPS) of the films. Moreover, the appearance of oxygen vacancies upon annealing at 1100 °C stimulates the drastic variation of the PL spectra of Pr³⁺ions due to the change of dominated defects, which participate in the excitation of Pr³⁺ion emission. In the latter case, the excitation of high energy PL bands in the 4f shell of Pr³⁺ions occurs with the excitation energy transfer through O vacancies. The results obtained are important for applications of HfO₂:Pr films in telecommunication technology.