World Journal of Condensed Matter Physics, 2015, 5, 220-231 Published Online August 2015 in SciRes. http://www.scirp.org/journal/wjcmp http://dx.doi.org/10.4236/wjcmp.2015.53023 How to cite this paper: Alwany, A.E.B., Samir, O.M., Algradee, M.A., Hafith, M.M. and Abdel-Rahim, M.A. (2015) Investiga- tion of the Effect of Film Thickness and Heat Treatment on the Optical Properties of TeSeSn Thin Films. World Journal of Condensed Matter Physics, 5, 220-231. http://dx.doi.org/10.4236/wjcmp.2015.53023 Investigation of the Effect of Film Thickness and Heat Treatment on the Optical Properties of TeSeSn Thin Films A. Elwhab B. Alwany 1 , O. M. Samir 1 , Mohammed A. Algradee 1 , M. M. Hafith 2 , M. A. Abdel-Rahim 2 1 Physics Department, Faculty of Science, Ibb University, Ibb, Yemen 2 Physics Department, Faculty of Science, Assuit University, Assuit, Egypt Email: abdualwhab@yahoo.com , algradi772001@yahoo.com Received 27 June 2015; accepted 18 August 2015; published 21 August 2015 Copyright © 2015 by authors and Scientific Research Publishing Inc. This work is licensed under the Creative Commons Attribution International License (CC BY). http://creativecommons.org/licenses/by/4.0/ Abstract Glassy substrates TeSeSn thin films were thermally evaporated onto chemically cleaned glass. The as-deposited (as-prepared) and annealed thin films were characterized by scanning electron mi- croscopy (SEM), X-ray diffraction (XRD) and optical transmission. The optical absorption of the as-prepared and annealed TeSeSn thin films is studied in the wavelength range of 300 nm - 900 nm. The direct optical energy gap (E g ) increases from 1.989 to 2.143 eV with increasing the thickness of the as-prepared films from 100 to 200 nm. The annealed TeSeSn films showed a decrease in the optical energy gap with increasing the annealing temperature. The effect of heat treatment on the lattice dielectric constant (ε L ) and carrier concentration (N) are also studied. Keywords Thin Film, Film Thickness, Annealing Temperature, Optical Properties 1. Introduction Chalcogenide glasses are used as photographic materials and have gained much importance recently. The short- comings of pure glassy Se used for photographic drums are its short lifetime and low sensitivity [1]. Certain ad- ditives are used to improve these properties. Recently, new optimistic applications of chalcogenide alloys have occurred in the field of infrared spectroscopy, lasers and fiber techniques [2] [3]. There are promising applica- tions in the field of laser surgery and radiometric low-temperature measurement. The transmission limits of se- lenium and tellurium glasses are now well known [4]. Selenium glasses exhibit a transmission range from 8 to