Electret states and current oscillations in the ferroelectric semiconductor TlGaSe₂

Abstract

Low-frequency current oscillations (LFCOs) have been observed for the first time in the ferroelectric semiconductor TlGaSe 2 . It is shown that LFCOs can be observed in specially undoped high-resistivity single crystals and in crystals after annealing for some hours within the incommensurate phase. LFCOs are shown to be due to non-linear current -voltage (I-V) characteristics of the crystals. The origin of the non-linearity of the I-V characteristics is based on the formation of electret states due to the capture of carriers by deep impurity centres. The possible influence of electret states on the peculiarities of different physical properties observed in these crystals is discussed.

Study of optical absorption in TlGaSe2:Zn2+ single crystals

“…They have already proved their applicability for many optoelectronic devices [4]. In particular, thallium chalcogenides attract much attention due to their low dimensionality, as well as interesting photoconductive properties, memory effects and optical second-harmonic generation [5][6][7][8].…”

Characterization of deep level defects and thermally stimulated depolarization phenomena in La-doped TlInS2 layered semiconductor

“…27,28 Recently, this phenomenon was observed in undoped TlGaSe 2 layered crystal, 30,31 which is belonged to A III B III C VI 2 chalcogenide materials family also. Thus, the electrets properties in A III B III C VI 2 materials are connected with semiconducting properties in same compounds.…”

“…The internal electric field induced by electrically active B5 centers in the temperature region of 190-230 K is the electrets field. 27,28,30,31 Materials, which are able to retain electric polarization over a long period of time and to create an internal static electric field, are known as electrets. 32,33 The term electrets was proposed over a century ago to describe a material that is the electrostatic equivalent of a magnet.…”

“…Recent studies have presented experimental evidence and discussed on possible theoretical models for the formation of electrets state in these materials, especially inside the region of IC-phase. 18,19,30,31 The nature of electrets state in TlInS 2 or TlGaSe 2 crystals is related to deep level defects within the temperature activation region that includes the IC-phase. Due to a lack of translational symmetry, TlInS 2 or TlGaSe 2 layered crystals within the temperature region of the existence of IC-modulated phase are the examples of aperiodic or quasiperiodic crystals, i.e., the basic structure with space group symmetry has a periodic modulation with wave vectors not belonging to the reciprocal lattice of the basic structure.…”

Effect of electric field on negative linear expansion of ferroelectric-semiconductor TlGaSe2

“…These polarized impurity states play an important role in the electrical and optical properties of TlGaSe 2 crystals. [13][14][15][16] According to the proposed mechanism, the interatomic distances depend on the electronic configuration of deep impurity centers, which can be changed under illumination. We concluded thus that it is the electric fields of polarized impurities that are responsible for the lattice deformation of TlGaSe 2 at low temperatures.…”