Temperature behavior of dielectric function spectra and optical transitions in TlGaS₂

Abstract

The dielectric function spectra of TlGaS 2 crystal with quasitwo-dimensional layered structure have been studied by means of spectroscopic elipsometry over the photon range 1.5-6.0 eV in the temperature range 100-400 K. The absolute values of the dielectric function show a sudden temperature-induced change around 180 and 280 K. The energy of the inter-band optical transitions retrieved from the dielectric function spectra display an abrupt temperature change around the same temperatures. Structural phase transitions are behind the observed change of electronic band structure of TlGaS 2 . Original Paper room temperature. The origin of CPs were assigned within the electronic band structure obtained from calculations based on density functional theory [9]. 1256 Y. Shim et al.: Temperature behavior of dielectric function spectra in TlGaS 2

Spectroscopic Ellipsometry Studies and Temperature Behaviour of the Dielectric Function of TlInS2 Layered Crystal

“…3. It is worth mentioning that a noticeably similar stepwiselike behaviour was observed for the temperature dependence of the CP parameters in TlGaS2 [32] and TlGaTe2 [25]. It should be noted that the temperature dependence of important critical points in the band structure of semiconductors can be explained by taking into account thermal expansion and electron-phonon interaction.…”

Characterisation of Planar Defects in Ternary Layered Chalcogenides for Electronic Devices

“…One such candidate systems are the ternary chalcogenides (e.g. TlGaSe 2 and TlGaS 2 ), which possess exotic properties such as low band gaps [2][3] and low thermal conductivity [4]. However, these materials are prone to atomic-scale structural defects, either from growth or from processing, which in turn can influence their electronic properties, resulting in significant changes of device characteristics.…”