11 research outputs found
Electronic properties and phase transitions in low-dimensional semiconductors
We present the first review of the current state of the literature on
electronic properties and phase transitions in TlX and TlMX2 (M = Ga, In; X =
Se, S, Te) compounds. These chalcogenides belong to a family of the
low-dimensional semiconductors possessing chain or layered structure. They are
of significant interest because of their highly anisotropic properties, semi-
and photoconductivity, non-linear effects in their I-V characteristics
(including a region of negative differential resistance), switching and memory
effects, second harmonic optical generation, relaxor behavior and potential
applications for optoelectronic devices. We review the crystal structure of TlX
and TlMX2 compounds, their transport properties under ambient conditions,
experimental and theoretical studies of the electronic structure, transport
properties and semiconductor-metal phase transitions under high pressure, and
sequences of temperature-induced structural phase transitions with intermediate
incommensurate states. Electronic nature of the ferroelectric phase transitions
in the above-mentioned compounds, as well as relaxor behavior, nanodomains and
possible occurrence of quantum dots in doped and irradiated crystals is
discussed.Comment: 70 pages, 38 figure
Low-temperature crystal structure, specific heat, and dielectric properties of lithium tetraborate
Coherent neutron powder diffraction experiments were carried out together with specific heat, dilatometry, and dielectric spectroscopy studies on Li2B4O7 enriched with B-11 isotope to 99.3% at low temperatures. Neither traces of phase transformations nor discontinuous changes in physical properties were observed. Negative thermal expansion, anomalous thermal behavior of selected interatomic distances/angles, isotropic displacement parameters on specific sites as well as dielectric constant were discussed in terms of dynamic lithium disorder. (C) 2010 American Institute of Physics. [doi:10.1063/1.3504244