Vibrational Spectra and Phase Transitions in Layered Semiconducting Ferroelectrics with TlGaSe2 Structure. I. Temperature Dependences of Parameters of the Raman Spectrum Lines of TlGaSe2

Abstract

AbstractRaman spectra of TlGaSe2 single crystals are obtained in the temperature range 85< T < 300 K, which includes the phase transition points. Fitting of the spectra, using the model of additive damped oscillators and a relaxator, yields quantitative information on parameters of the lines. No critical rise of the relaxation time is detected near phase transitions. On the other hand, the strength of the relaxator experiences an approximately twofold increase. An anomalous behavior of parameters of the lines is observed near phase transitions, which is thought to be associated with ordering processes. The lowest‐frequency lines in the 15 cm−1 region are interpreted as the lines which correspond to rigid‐layer modes.