Thickness dependence of optical parameters for Ge–Se–Te thin films

Abstract

The present work deals with thickness dependent study of the thin films of Ge 10Se 90 − x Te x ( x = 0, 10) chalcogenide glasses. Bulk samples of Ge 10Se 90 and Ge 10Se 80Te 10 have been prepared by melt quenching technique. Thin films (thickness d = 800 nm and 1100 nm) of the prepared samples have been deposited on glass substrate using vacuum evaporation technique. The optical parameters i.e. optical band gap ( E g opt), absorption coefficient ( α), refractive index ( n) and extinction coefficient ( k) are calculated from the transmission spectrum in the range 400–1500 nm. The optical band gap decreases with the increase of thickness from 1.87 ± 0.01 eV ( d = 800 nm) to 1.80 ± 0.01 eV ( d = 1100 nm) for Ge 10Se 90 and from 1.62 ± 0.01 eV ( d = 800 nm) to 1.48 ± 0.01 eV ( d = 1100 nm) for Ge 10Se 80Te 10 thin films.