Enhancement of the luminescent characteristics of Li-doped CaTiO3: Pr3+ thin films grown by pulsed laser deposition

The influence of Li doping on the crystallization, surface morphology and luminescent properties of CaTiO3 : Pr3+ films has been investigated. The films were grown on Al2O3 (0001) substrates using the pulsed laser deposition method under different oxygen pressures. The substrate temperature was fixed at 700 degrees C and the range of oxygen pressure was 100-400 mTorr. The crystallinity and surface morphology of the films were investigated using x-ray diffraction and atomic force microscopy, respectively. The emitted radiation at 322 nm excitation was dominated by a red emission peak at 613 nm radiated from the transition of D-1(2) -> H-3(4) of Pr3+ ions. In particular, the incorporation of Li+ ions into the CaTiO3 lattice could induce the increase in the intensity of the photoluminescence. The enhanced luminescence may result not only from the improved crystallinity but also from the reduced internal reflections caused by rougher surfaces. The luminescent intensity and surface roughness exhibited similar behaviour as a function of the oxygen pressure.