Temperature dependence of dielectric function spectra and interband optical transitions in layered TlInS2

The temperature behavior of the dielectric function spectra and related interband optical transitions in layered TlInS2 with a structural ferroelectric phase transition via an intermediate incommensurate phase has been studied over the temperature range of 80–400 K by using spectroscopic ellipsometry in the photon energy region from 1.5 to 4.2 eV. Both (100) and (001) surfaces of TlInS2 have been examined, and the collected ellipsometric data have allowed retrieving diagonal components of the dielectric function tensor. Standard critical point analysis of the retrieved components shows that energy and broadening of the interband optical transitions subsequently experience remarkable changes upon reaching the points of phase transitions. The obtained results provide a better insight into optical properties and the electronic structure of incommensurate semiconductors-ferroelectrics.The temperature behavior of the dielectric function spectra and related interband optical transitions in layered TlInS2 with a structural ferroelectric phase transition via an intermediate incommensurate phase has been studied over the temperature range of 80–400 K by using spectroscopic ellipsometry in the photon energy region from 1.5 to 4.2 eV. Both (100) and (001) surfaces of TlInS2 have been examined, and the collected ellipsometric data have allowed retrieving diagonal components of the dielectric function tensor. Standard critical point analysis of the retrieved components shows that energy and broadening of the interband optical transitions subsequently experience remarkable changes upon reaching the points of phase transitions. The obtained results provide a better insight into optical properties and the electronic structure of incommensurate semiconductors-ferroelectrics.