Low temperature absorption edge and photoluminescence study in TlIn(Se1−xSx)2 layered mixed crystals

Abstract

Transmission on TlIn(Se1−xSx)2 mixed crystals (0.25 ≤ x ≤ 1) were carried out in the 400–800 nm wavelength range at T = 10 K. Band gap energies of the studied crystals were obtained using the derivative spectra of transmittance. The compositional dependence of direct band gap energy at T = 10 K revealed that as sulfur composition is increased in the mixed crystals, the direct band gap energy rises from 2.26 eV (x = 0.25) to 2.56 eV (x = 1).Photoluminescence spectra of TlIn(Se1−xSx)2 mixed crystals were studied in the wavelength region of 400–620 nm at T = 10 K. The observed bands were attributed to the transitions of electrons from shallow donor levels to the valence band. The shift of the PL bands to higher energies with elevating sulfur content was revealed. Moreover, the composition ratio of the mixed crystals was obtained from the energy dispersive spectroscopy measurements.