Optical, electrical conduction and dielectric properties of TlGaSe2 layered single crystal

The optical properties of layered single crystals of TlGaSe2 have been studied. The spectral and optical parameters have been determined using spectrophotometric measurements of transmittance and reflectance in the wavelength range 200-2500 nm. The dispersion curve of the refractive index shows an anomalous dispersion in the absorption region and a normal one in the transmitted region. The determined direct and indirect band gaps are 2.08 and 1.93 eV, respectively. The measured DC electrical conduction of this sample decreases with decreasing temperature. The values of conductivity activation energy are calculated as 301 meV for high temperature region and 48 meV for low temperature region. Results are discussed in terms of electron hopping between localized states. The AC electrical conduction as a function of frequency shows a power law with an index slightly less than one. Also, it shows a slight variation with temperature in agreement with CBH model. There is a significant increase with temperature at low frequencies in both the real dielectric constant and the dielectric loss tangent.