FUNDAMENTAL OPTICAL-ABSORPTION EDGE AND EXCITON-PHONON INTERACTION INCU6PS5BR SUPERIONIC FERROELASTIC

The absorption edge of monocrystalline Cu6PS5Br was studied in the 4.2 -505 K temperature range. At low temperatures (T < 180 K), Wannier-Mot t s-excitons were detected at the absorption edge as well as in the ph otoluminescence spectra and, their basic parameters at 77 K were estim ated. The mechanisms of exciton-photon interaction resulting in expone ntial absorption edge and Urbach's tail at temperatures T > 200 K were analyzed and interpreted in the framework of the Dow-Redfield theory. Two types of structural disorder affecting the optical absorption tai l were studied. (C) 1998 Elsevier Science S.A. All rights reserved.