OPTICAL-ABSORPTION SPECTRA OF REDUCED TRANSITION-METAL ION-DOPED SRTIO3

The optical absorption spectra of SrTiO//3 doped with V, Cr, Mn, Fe, Co, and Ni have been measured as a function of reduction temperature. The high-temperature reduced state was frozen in the crystal by rapid quenching to room temperature. Low-temperature reduction approximately less than 1100 degree C generally produces low valency states of the dopants, but at higher reduction temperatures totally different absorption spectra are produced. These spectra are thought to be intimately related to some aggregation of the high density of oxygen vacancies produced upon high-temperature reduction.