Type of Optical Transitions at the Fundamental Absorption Edge in TlGaSe2 and TlInS2 Crystals Subjected to γ-Radiation

Abstract

The effect of γ-radiation on the optical properties of layered TlGaSe₂ and TlInS₂ crystals has been studied within a wavelength range of 400–1100 nm at 300 K. By means of analysis of optical absorption spectra, the energies of direct and indirect optical interbend transitions before and after γ-irradiation have been determined. It has been shown that the energies of direct and indirect nonforbidden optical transitions grow with accumulation of γ-radiation dose within 0–25 Мrad in TlGaSe₂ and TlInS₂ single crystals from E_gd = 2.06 eV and E_gi = 1.90 eV at D = 0 Мrad to E_gd = 2.11 eV and E_gi = 1.98 eV at D = 25 Мrad for TlGaSe₂ crystals and from E_gd = 2.32 eV and E_gi = 2.27 eV at D = 0 Мrad to E_gd = 2.35 eV and E_gi = 2.32 eV at D = 25 Мrad for TlInS₂ crystals. A decrease in the transmission coefficient at doses from 0 to 5 Mrad with a further increase in the transmission coefficient at a radiation dose of D = 25 Мrad is observed.