Theoretical characterization and band gap tuning of Snx(GeSe2)100-x thin films

Abstract

The ternary compounds Snx(GeSe2)100-x (0 ≤ x ≤ 24 at. %) were prepared in glassy thin films. Using the chemical bond approach, theoretical calculations of effects of Sn content on mean coordination number (CN), constraints number (Ns), molar volume (Vm), compactness (δ), heat of atomization (Hs), cohesive energy (CE), overall difference of electronegativity (Δχ) as well as the degree of iconicity (Ion) were discussed. Optical absorbance has been measured in order to evaluate experimentally the band gap (Eg) and the band tail's width (Ee). In addition, conduction-valence bands positions were estimated when changing Sn content. Increasing Sn content from 0 to 24 at. %, decreases Eg from 2.01 to 1.28 eV. Three theoretical estimations of the variations of the band gap with Sn content were critically compared to experimental values. Obviously, the combination of the estimated band gap from Δχ and contributions of the formed bonds gives the best adjustment.