Spectroscopic ellipsometry of SrTiO3 crystals applied to antiferrodistortive surface phase transition

Abstract

This work is devoted to the ellipsometric study of antiferrodistortive (AFD) O1h → D184h cubic-to-tetragonal phase transition (PT) of SrTiO3 surface. Strong influence of surface defect structure on magnitude and temperature evolutions of surface refractive index related to PT was found and investigated. It is shown that even small surface imperfections result in enhancement and strong changes of the surface refractive index when approaching the temperature of PT. This effect is caused by emergence and evolutions in the surface of the structural changes corresponding to order parameter at the temperatures sufficiently higher than transition temperature in the bulk. In the case of structurally perfect crystal surface, the features of the temperature dependence of surface refractive index appeared to be very small and visible at the temperatures a little smaller than transition temperature for bulk that agrees well with predictions of Kaganov-Omel'yanchuk theory. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.