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

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 Egd = 2.06 eV and Egi = 1.90 eV at D = 0 Мrad to Egd = 2.11 eV and Egi = 1.98 eV at D = 25 Мrad for TlGaSe2 crystals and from Egd = 2.32 eV and Egi = 2.27 eV at D = 0 Мrad to Egd = 2.35 eV and Egi = 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.

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