Fluctuon type carrier localization near charged defect

Abstract

The consideration of the physical mechanism of carrier localization in vicinity of some charged lattice imperfection in ABO₃ perovskites is performed. The calculations had shown that because of imperfections the interaction of an electron with transverse phonons arises while it interacts only with longitudinal phonons in ideal lattice. As a result electron is localized on one of equivalent cations in the nearest neighbour of the imperfection. The criterion of electron localization on one out of two, four, six and eight equivalent cations for the cases respectively of oxygen vacancy, interstitial impurity, substitutional defects in B and A positions is derived. The criterion looks like that for pseudo-Jahn-Teller effect. The fulfillment of the criterion for 2 equivalent positions proves that the origin of Ta⁴⁺ ions observed in vicinity of oxygen vacancy in KTaO₃ can be an electron localization on fluctuon type state.

Key Words:

• carrier localization
• defects
• oxygen vacancy