Optical Investigations of In2Se2.7Sb0.3 Thin Films Prepared by Thermal Evaporation Technique Piyush Patel 1,a* , Vimal Patel 1,b , Sandip Vyas 1,c , Jaydev Patel 1 , and Himanshu Pavagadhi 1 1 Department of Physics, School of Science, Gujarat University, Ahmedabad, 380009, Gujarat, India. a piyush_patel130@yahoo.com, b vimalpatel082013@gmail.com, c s_m_vyas_msu@yahoo.com, Keywords: Thin Films, Absorption Coefficient (α), refractive index (η), Extinction Coefficient (k) and Optical Band Gap (Eg). Abstract: The III-VI compound semiconductors are important for the fabrication of ionizing radiation detectors, solid-state electrodes, and photosensitive heterostructures, solar cell as well as ionic batteries. In this paper, In2Se2.7Sb0.3 thin films have been grown by thermal evaporation technique onto a with chemically clean glass substrate. Amorphous nature of the films has been discovered by UV-VIS spectrophotometer. The analysis by absorption spectra within the spectral range 200nm -900 nm has been used for the optical characterization of thin films. From these data the optical constants (absorption coefficient (α), refractive index (η), extinction coefficient (k)) and optical band gap (Eg) are studied. The results were discussed, and reported in detail. Introduction Normally III-VI semiconductors having a layered structured family. The energy gap of InSe at room temperature is 1.3 eV, which makes it an attractive material for solar energy conversion [1- 5] diodes [6], infrared devices, and lasers [4]. It is also used as promising material for application in solid solution electrode, opto-electronic devices etc. But little work has been reported on the thin films [7]. But our interest in the In2Se3 is an n-type semiconductor in the form of hexagonal structure with a direct band gap of 1.7 eV [8]. They are attractive semiconductors for potential applications in batteries and photo-electrochemical cells [9-14]. The In2Se3–Sb2Se3 system has been investigated at least three times [15-17]. According to Wobst [16], this system is a quasibinary cross section of a ternary system; no defined compound has been observed in it. Belotskii et al. [15] observed a finite region of In2Se3 based solid solution. According to Guliev et al. [17] found finite solid solutions of substitution based on the binary compounds and an incongruously melting compound with the composition InSbSe3, which undergoes a polymorphic transition at 525°C. In the present work, the effect of film thickness on the optical properties of In2Se2.7Sb0.3 over the thickness range 0.625 kÅ – 1.500 kÅ has been investigated. An attempt has been made to evaluate the optical constants (like absorption constant (α), refractive index (η), extinction constant (k)) and optical band gap (Eg)) are studied. Experimental Method The elemental materials Indium(In), Selenium(Se) and Antimony(Sb) of 99.999 %( 5N) purity were used for the preparation of the alloy with a stoichiometric proportion and sealed in a quartz ampoule of 25 cm in length and 1 cm in diameter under the vacuum of the order of 10 -5 torr. The ampoule containing charges was placed in a horizontal alloy mixing furnace at the temperature 700 0 C for 48 hours, during which it was continuously rocked and rotated for proper mixing and reaction. The ingot was then cooled to room temperature over a period of 24 hours. The crystal of Materials Science Forum Submitted: 2018-07-08 ISSN: 1662-9752, Vol. 969, pp 355-360 Revised: 2019-02-26 © 2019 Trans Tech Publications Ltd, Switzerland Accepted: 2019-02-26 Online: 2019-08-30 All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications Ltd, www.scientific.net. (#510007872-24/08/19,05:15:01)