Interband Critical Points in Tlga<i><sub>x</Sub>< Layered Mixed Crystals (0 ≤ <i>x</I> ≤ 1)

Abstract

The layered semiconducting TlGaxIn1-xS2 mixed crystals (0 <= x <= 1) were studied by spectroscopic ellipsometry measurements in the 1.2-6.2 eV spectral range at room temperature. The spectral dependence of the components of the complex dielectric function, refractive index and extinction coefficient were revealed using an optical model. The interband transition energies in the studied samples were found from the analysis of the second-energy derivative spectra of the complex dielectric function. The variation of the obtained energies with composition were plotted to see the effect of the substitution of indium with gallium. Moreover, a simple diagram showing the revealed transitions in the available electronic band structure was given for TlGaS2 single crystals. (C) 2013 Elsevier B.V. All rights