Chemical Bonding and Polarons in Sn2P2S(Se)6 Ferroelectrics

Abstract

For ferroelectric-semiconductor Sn2P2Se6 the low temperature dielectric relaxation was found to be similar to that observed in Sn2P2S6 analog. This relaxation behavior was explained as an evidence of small polaron dynamics in the lattices with different covalence of bonds between atoms at presence of tin and sulfur (selenium) vacancies. The calculations in LDA approach of the electron band structure and the energy levels of intrinsic defects together with analysis of the Raman spectra and photoluminescence temperature behavior give evidences of polaron dynamics joining with donor-acceptor compensation processes.