Memory effect and new polarized state in the incommensurate phase of TlGaSe2 ferroelectric-semiconductor

Abstract

The structural, electrical, and thermal properties of the ferroelectric-semiconductor TlGaSe2 have been investigated after the thermal annealing of crystals inside the incommensurate (INC) phase for a few hours at the annealing temperature (T-ann). It is found that all outlined physical parameters of TlGaSe2 are significantly modified after the annealing process. Besides the well-known memory effect, thermal annealing within the INC phase leads to previously unknown anomalies of the different physical properties of TlGaSe2 crystals at temperatures quite far from the INC-phase. To explain the experimental results it is supposed that annealing leads to the formation of a new polarized state that influences most of the physical parameters of the crystals. This outstanding feature of the annealing effect in TlGaSe2 crystals allows us to reveal some new phase transitions that take place in TlGaSe2 crystals in the 140-180 K temperature range. (C) 2011 American Institute of Physics. [doi:10.1063/1.3606465]