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The effect of electric field on the thermal expansion of the TlGaSe2 ferroelectric-semiconductor with a layer crystalline structure has been investigated. A strong transformation of negative linear expansion coefficient in the layer plane has been observed as a result of the applied electric field. It was concluded that internal electric fields created by local polarized states in the ferroelectric- semiconductor are responsible for a negative thermal expansion and its behavior under the electric field. Predominantly, the electrostriction effect is the driving mechanism of the lattice deformation of TlGaSe2 crystals at low temperatures. [ABSTRACT FROM AUTHOR]

The effect of thermal annealing within the incommensurate phase (memory effect) on thermal expansion of ferroelectric-semiconductor crystal TlGaSe2 has been investigated. Strong transformation of linear expansion coefficients both in the layers plane and in the direction perpendicular to the layers has been observed for the first time as a result of annealing. It is supposed that internal electric fields (electret states) activated during the annealing greatly effect the dimension of the crystal via electrostriction. [ABSTRACT FROM AUTHOR]

The effect of thermal annealing within the incommensurate phase (memory effect) on thermal expansion of ferroelectric-semiconductor crystal TlGaSe2 has been investigated. Strong transformation of linear expansion coefficients both in the layers plane and in the direction perpendicular to the layers has been observed for the first time as a result of annealing. It is supposed that internal electric fields (electret states) activated during the annealing greatly effect the dimension of the crystal via electrostriction. [ABSTRACT FROM AUTHOR]

The electrical properties of TlGa[Se.sub.2] ferroelectric-semiconductor with layer crystalline structure in the dielectric parallel to the layers plane is analyzed by impedance spectroscopy. Charge disproportination is the main feature of the phase transition that has led to the charge density modulation in one crystallographic direction perpendicular to the layers plane of the crystal.

The article presents a comparative analysis of the temperature dependences of thermal expansion as exhibited by the different crystals and the various layered crystalline structure. The presence of the negative area compressibility is shown to be the main factor that leads to negative thermal expansion in the layered structures.

Several analyses are conducted to explain the impact of annealing on the incommensurate phase exhibited by the ferroelectric semiconductor TlIn[S.sub.2].

The effect of electric field on the thermal expansion of the TIGa[Se.sub.2] ferroelectric-semiconductor with a layer crystalline structure is examined. The studies have shown that the internal electric fields created by local polarized states in the ferroelectric-semiconductor are the reason for a negative thermal expansion and its behavior under the electric field.

The effect of thermal annealing within the incommensurate phase or memory effect on thermal expansion of ferroelectric-semiconductor crystal TlGa[Se.sub.2] is examined. The studies have shown that internal electric fields activated during the annealing have affected the dimension of the crystal via electrostriction.

Temperature-dependent reversal of the rectifying polarity is observed in Au/TlGa[Se.sub.2] Schottky junctions. The interface permittivity is changed as a result of phase transitions, thus changing the Schottky barrier's width and the contributions of tunneling and thermally assisted transitions.

Temperature-dependent reversal of the rectifying polarity has been observed in Au/TlGaSe2 Schottky junctions. To explain the experimental findings the important role of the tunneling current was taken into account. Besides, it was found that the temperature range, where the rectifying polarity reversal is observed, coincides with the temperature interval where an electronic phase transition takes place in TlGaSe2 crystals. The interface permittivity is significantly changed as a result of phase transitions, thus changing the Schottky barrier’s width and consequently the contributions of tunneling and usual thermally assisted transitions. Schottky barrier method becomes a powerful tool investigating phase transitions in semiconductors. [ABSTRACT FROM AUTHOR]

Abstract: The influence of electric field and current flow on the current-voltage (I-V) characteristics of TlGaSe2 layered semiconductor was investigated by using a two-point probe measurement system. Threshold-type switching in I-V characteristics associated with current-controlled memory effect was observed in all investigated samples. Observed switching characteristic is close to the most experimentally realizable memristive systems. Experimental findings were analyzed by using a model of metal-insulator-semiconductor-insulator-metal (MISIM) structure having memristive behavior. [ABSTRACT FROM AUTHOR]

Photoelectric relaxation spectroscopy (photoinduced current relaxation spectroscopy, PICTS) is used to study pure and La-doped single crystals of TlInS2. The characteristics of electrically active defects are determined including the capture cross section for charge carriers, the thermal activation energy, and the temperature interval within which the charge state of a defect varies. The pyroelectric properties of TlInS2:La are studied. The defect responsible for the anomalies in the pyrocurrent is identified. [ABSTRACT FROM AUTHOR]

Abstract: Second-harmonic generation effects have been investigated in TlGaSe2 layered crystal over a temperature range where ferroelectric phase exists. Pronounced periodical changes of the second-harmonic signal with temperature have been discovered. The observed effect is explained within the phase synchronism condition which changes with the temperature. The main mechanism of the thermal expansion of the sample in the observed phenomenon is explained. [Copyright &y& Elsevier]

Highlights from the article: Synthesis, Powder X-Ray Diffraction, and Ab Initio Study of TlInSe2: Analysis of Its Thermoelectric Properties Seyidov, and co-workers report first-principles calculations of the Seebeck coefficient in TlInSe SB 2 sb . The hybridization of Se and Tl orbitals near the top of valence band as well as Se, Tl, and In orbitals in conduction band may lead to giant values of the Seebeck coefficient as it is reported in literature.