Enhanced exciton-phonon efficiency in photoluminescence of SrTiO3 :Er films covered on ZnO nanorods

Characteristics of light emission of Er-doped SrTiO₃ (STO) thin films (STO : Er) deposited on different surface morphologies by a sputtering technique were investigated. The luminescence efficiency of Er-doped STO films covered on ZnO nanorods was greater than deposited directly on Si (100) substrates in all specimens. Formation of one-dimensional well-aligned ZnO nanorods has been achieved using a simple aqueous solution method at low temperatures. The dependence of luminescence efficiency on Er³⁺ concentrations and annealing temperatures in the Er-doped STO films is governed by crystallinity and ion-ion interaction. The photoluminescence (PL) measurement of the Er-doped STO films covered on ZnO nanorods show that the much stronger intensity of green light is observed at annealing temperature 700 °C and 3 mol% Er³⁺-doped concentration. The presence of clusters as the Er concentration exceed 3 mol% will diminish the emission intensity. Besides, concentration quenching was observed on STO films containing 5 mol% Er dopant. The phenomenon was attributed to energy transference and cross relaxation between closely sited Er³⁺ ions in the STO lattice. We also showed that the quenching mechanism of the luminescent intensity is evidently relational with Er-doped concentrations and annealing temperatures. The photoluminescence properties suggest that adding a 3 mol% Er-doped STO films covered on ZnO nanorods is the optimal choice for optoelectronic device applications.