Characteristics of Optical and Photoconductive Properties in Bulk and Thin Film of TlS₂Single Crystals

Abstract

The photoconductivity measurements were carried out for bulk single crystals of TlS2 by using the steady state (dc) method in order to elucidate the nature of the dc photoconductivity in these crystals. The photoconductivity measurements were carried out in the temperature range of 77-300 K, excitation intensity range of 2150-5050 lx, applied voltage range of 10-25 V, and wavelength range of 400-915 nm. As a result of the dc photoconductivity, the temperature dependence of the energy gap width was described and the temperature coefficient of the band gap was determined. Reflectance and transmittance spectra of the TlS2 thin films were measured in the incident photon energy range of 2.1-2.45 eV and in the temperature range of 77-300 K. With the aid of these spectra, the temperature dependence of optical transports and parameters were elucidated. In the low energy region of the studied incident photon energy range, the above-mentioned spectra were analyzed for describing the refractive index as a function of wavelength. As results of the refractive index-wavelength variations, both the oscillator and dispersion energies of the refractive index were thereafter estimated.