We have grown SrTiO3 thin films by rf-sputtering and studied its photoluminescence (PL) property after postannealing treatments. While the as-grown film does not show any PL signal, visible frequency PL emissions are induced by high temperature (T>550 °C) annealing. When subsequent low-T (50 °C) and long term (>8 months) annealing was made, the PL-spectra evolved into another pattern in which four distinct luminescence peaks appear simultaneously at λ=1.8, 2.2, 2.7, and 3.1 eV. We propose that these remarkable room temperature PL effects are due to both metastable and energetically stabilized defect states formed inside the band gap.
Bibliographical noteFunding Information:
We thank S. Han, J. Yu, and Y. Choi for useful discussions. This work was supported by Nuclear Research and Development Program of the Korea Science and Engineering Foundation (KOSEF), grant funded by the Korean government (MEST, under Grant No. 20090067238). D.W.K. was supported by the Pioneer Research Center Program (Grant No. 2009-0083007) through the National Research Foundation of Korea, grant funded by the Korea government (MEST). Y.-D.K. was supported by Seoul R & BD program (Grant No. 10543). S.J.K. and M.K. were supported by the Korea Science and Engineering Foundation (KOSEF) (Grant No. R0A-2007-000-10014-0).