Electronic properties and phase transitions in low-dimensional semiconductors

Abstract

We present the first review of the current state of the literatureon electronic properties and phase transitions in TlX andTlMX2 (M = Ga,In; X = Se, S, Te) compounds. These chalcogenides belong to a family of the low-dimensionalsemiconductors possessing chain or layered structure. They are of significant interest becauseof their highly anisotropic properties, semi- and photoconductivity, nonlinear effects in theirI–V characteristics (including a region of negative differential resistance), switching andmemory effects, second harmonic optical generation, relaxor behavior and potentialapplications for optoelectronic devices. We review the crystal structure of TlX andTlMX2 compounds, their transport properties under ambient conditions, experimental and theoreticalstudies of the electronic structure, transport properties and semiconductor–metal phasetransitions under high pressure, and sequences of temperature-induced structural phasetransitions with intermediate incommensurate states. The electronic nature of theferroelectric phase transitions in the above-mentioned compounds, as well as relaxorbehavior, nanodomains and possible occurrence of quantum dots in doped and irradiatedcrystals is discussed.