Light-induced absorption and properties of shallow impurity levels in undoped and Ce-doped BaTiO3

Spectral and temporal characteristics of light-induced absorption for BaTiO3 crystals undoped and doped with various amounts of Ce were investigated and compared. Dark decay of light-induced absorption with two time constants corresponding to two shallow levels was observed in all crystals investigated. Light-induced absorption spectra were then resolved into two components, slow and fast, according to the dark-decay time constants. The resolved spectra reveal that in all the undoped and Ce-doped crystals the two shallow levels have the same defect origins, independently of doping. The thermal activation energies of the two shallow levels were deduced to be similar to 0.7 and similar to 0.5 eV in all crystals, and the 0.7-eV shallow level is attributed to Fe4+/5+. Some other important parameters for the two shallow levels were also determined. (C) 1998 Optical Society of America.