Quantitative determination of charge transfer parameters of photorefractive BaTiO₃:Rh from EPR-based defect studies

Abstract

Optical absorption bands can be used as fingerprints of defects and their charge states in insulators and semiconductors. On the basis of the photochromicity usually shown by such materials, a method is introduced by which the optical bands are assigned to the defects and their charge states. It is based on simultaneous measurements of the light-induced changes of the optical absorption and of the corresponding EPR signals. Moreover, indirectly optical bands of EPR-silent defects can also be labelled in this way, strongly widening the scope of EPR based defect studies. We apply this method to the infrared-sensitive photorefractive system BaTiO 3 :Rh, where illumination leads to recharging among the valence states Rh 5+ , Rh 4+ and Rh 3+ . The values of all parameters governing the charge transfers responsible are inferred from the magnitude of the absorption bands, the absolute determination of their absorption cross-sections and the kinetics of the absorption changes under illumination. In contrast to previous investigations, these parameters are deduced independently of photorefractive measurements.

Theoretical Investigations on the Spin Hamiltonian Parameters and Local Structure for the Tetragonal Pt 3 + Center in BaTiO 3

“…BaTiO 3 is a ferroelectric with a number of interesting and important properties, such as dielectric [1], pyroelectric [2], ferroelectric [3][4][5][6], electric [7,8], mechanic [9], optical [10,11], photorefractive [12,13], ferromagnetism [14] and structural properties [15,16] which have been extensively investigated. On the other hand, transition-metal impurities (e.g., Pt 3+ ) can locally change the above properties by inducing unique impurity energy levels and related local distortions.…”