STUDIES OF SHALLOW LEVELS IN UNDOPED AND RHODIUM-DOPED BARIUM-TITANATE

Spectral and temporal characteristics of light-induced absorption for an undoped and a Rh-doped as-grown BaTiO3 crystal were investigated an d compared. Two dark-decay time constants corresponding to two shallow levels were observed: 40 ms and 1.2 s for undoped BaTiO3 and 39 ms an d 3.4 s for Rh-doped BaTiO3. The light-induced absorption spectra were resolved into two components according to the dark-decay time constan ts. The resolved spectra reveal that one shallow level in Rh-doped BaT iO3 and one in undoped BaTiO3 are caused by a same impurity defect. Th e thermal activation energies of these levels were determined to be 0. 53 and 0.7 eV for undoped BaTiO3 and 0.57 and 0.8 eV for Rh-doped BaTi O3. The 0.8-eV shallow level in BaTiO3:Rh is caused by Rh4+/5+; the ot her level, 0.57 eV, is the one that has the same defect origin as the 0.53 eV level in undoped BaTiO3. Other parameters for the shallow leve ls are also given. (C) 1998 Optical Society of America.