Charged Defects as an Origin of the Memory Effect in Incommensurate Phase of TlInS2 Ferroelectric--Semiconductors

The effects of annealing within the incommensurate phase and doping with the lanthanum impurity on the dielectric function $\varepsilon$ of the TlInS 2 single crystals have been investigated. It is shown that illumination and application of external electric field transform the $\varepsilon (T)$ dependences for both the annealed and doped samples in the same manner. The inference is made that the correlation between observed effects is conditioned by the internal electric fields induced either by activation (polarization) of native defects during the annealing procedure or after the doping the crystals with active La centers.