Ambient dependence of visible emissions in SrTiO3

We investigated the visible emission property of SrTiO3 (STO) single crystals with high temperature annealing in some ambient conditions. We found that the green emission in STO, which should be associated with intermediate states originating from functional ionic defects inside the samples, such as cation/oxygen vacancies, showed strong ambient dependence. While high temperature annealing in the O-2 atmosphere suppressed the intensity of visible emission, annealing in an O-2-free atmosphere, such as N-2 or H-2, increased it. The broad visible emissions were fitted with three sub-modes, whose intensities showed different evolutions with respect to the ambient condition. Our study demonstrated the systematic development of defect states with the amount of the oxygen vacancies in STO.