Optical properties and photo-induced memory effect related with structural phase transition in TlGaS2 Original Research Article

Anomalies of the temperature coefficient of exciton absorption peak shift of TlGaS2 were observed around 180–190 and 240–250 K. Some Raman lines were found to split at temperatures around 230–260 K. At low temperatures the light irradiation with the photon energy above the band gap energy caused a memory effect of photoluminescence quenching. This effect was observed for the emission appearing at 609 nm. Restoration of this photoluminescence quenching occurred with temperature range of 180–270 K. Complete recovery was attained at temperature above 270 K. The correspondences among the temperature ranges of the exciton absorption peak shift anomalies, the Raman line splitting, and the disappearance of the memory effect are considered to show that in TlGaS2 successive phase transitions occur around 180–190 and 230–260 K.