Up-conversion photoluminescence and dielectric properties of pulsed-laser-ablated (Bi, Er)4Ti3O12 thin films grown with three different orientations

Epitaxial (001)-, (118)-, and (104)-oriented Bi 3.95 Er 0.05 Ti 3 O 12 (BErT) films were reproducibly obtained by pulsed-laser-ablated method, and the (100)-, (110)-, and (111)-oriented Nb-doped SrTiO 3 (NSTO) was used as substrates, respectively. X-ray diffraction indicated that the epitaxial orientation relation BErT (001)‖NSTO (100), BErT (118)‖NSTO (110), and BErT (104)‖NSTO (111) are effective for BErT thin films on NSTO substrates in all cases. The spectral analysis indicates that the up-conversion (UC) luminescence spectra of thin films contain a red light emission band centered at 660 nm and two green light emission bands centered at 525 and 548 nm. Furthermore, a strong orientation-dependent UC luminescence was also observed. The (104)-oriented thin film reveals an approximately 7 times higher fluorescence intensity than that of the (118)-oriented thin film, which in turn has an about 3 times higher fluorescence intensity than the (001)-oriented BErT thin film. The dependence of photoluminescence on the film orientation can be attributed to the reflection of aligned grains toward incident light. Accordingly, the dielectric constant of (104)-, (118)-, and (001)-oriented BErT films is 195, 183, and 158 at the frequency of 100 kHz, respectively, thus demonstrating the dielectric anisotropy.