Applicability of different models of energy bandgap and refractive index for chalcogenide thin films Ekta Sharma a,⇑ , Pankaj Sharma a,b a Department of Physics & Materials Science, Jaypee University of Information Technology, Waknaghat 173234, Himachal Pradesh, India b Applied Science Department, National Institute of Technical Teachers Training & Research, Chandigarh - 160019, India article info Article history: Received 18 December 2019 Received in revised form 8 January 2020 Accepted 16 January 2020 Available online xxxx Keywords: Optical energy gap Refractive index Chalcogenide glasses Thin films Melt-Quench technique abstract The optical parameters are critical factors for the development of optoelectronic devices. Here the authors report the study of optical parameters based on some empirical relationship for Ga doped Ge- Te-Se. These relationships are based on the specific models proposed for the calculation of binary, tern- ary, and quaternary chalcogenide glasses for the specific range of energy gap. The empirically calculated values of optical parameters from these models are compared with the experimental value of the chalco- genide thin films. The values of refractive index have been calculated from the optical bandgap. Some relations proposed by different authors show good agreement between the experimental and calculated values. It has been concluded that Ravindra & Gupta, Reddy & Duffy, Kumar & Singh, and Reddy provide the satisfactory results. Ó 2020 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of the scientific committee of the International Confer- ence on Advanced Materials and Nanotechnology. 1. Introduction Chalcogenide glasses play a significant role in the scientific and technological applications in optoelectronic, IR-fiber and photonic devices [1–3]. Chalcogenide glasses consist of one or more chalco- gen element like Sulphur (S), Selenium (Se), Tellurium (Te) with trivalent or tetravalent element like Germanium (Ge), Indium (In), Gallium (Ga), Arsenic (As). These glasses are getting more interest because of their linear and non-linear optical applications [1–3]. The chalcogen elements possess an increasing order of metallic character with the increasing in their atomic masses from S to Te. Amorphous chalcogenide glasses are known to be soft semiconductors. They are soft because of their structural flexibility and absence of long-range order and semiconductors because they possess band gap between 1 and 3 eV [4]. The two fundamental properties have estimated the electronic and optical behaviour of semiconductors are refractive index and the optical energy gap. Generally, the refractive index is a property of a material which measures the transparency, whereas the energy gap can be esti- mated from the threshold of photon absorption in the semiconduc- tor. These two properties play a vital role in optoelectronic applications like a light-emitting diode, optical fibers and photodi- odes etc. The empirical properties like dielectric constant, atomic polarizability are dependent on the refractive index. The refractive index of a semiconductor shows totally dependent behaviour on the band gap. The inversely proportional relationship exists between both the parameters make the material suitable for opto- electronic applications. R.S. Indolia [5] reported the relationship of refractive index with optical energy gap, and average energy gap for II-VI and III-V group of semiconductors. S. K. Tripathy [6] reported the refractive indices of semiconductors from energy gap for different group elements. The main objective of the present work is to apply the different model proposed for elaborating the connection between refractive index and the optical bandgap for thermally deposited Ge 10 Te 80 - Se 10-x Ga x (x = 0, 4 and 8) thin films. This study will help to get empirically an idea to identify theoretical models for the calcula- tion of optical parameters. The value of the experimental refractive index at the wavelength (2.6 mm) have been obtained by using Swanepoel method [7]. The optical band gap has been evaluated by Tauc method [8]. By using the experimental value of optical band gap, the refractive index has been calculated by using the dif- ferent relations taken from literature [5–6,10–19]. 2. Experimental technique Conventional melt quenching approach has been adopted to prepare glassy alloys of Ge 10 Te 80 Se 10-x Ga x (x = 0, 4 and 8) amor- phous systems. The material of 5 N purity weighed according to https://doi.org/10.1016/j.matpr.2020.01.342 2214-7853/Ó 2020 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of the scientific committee of the International Conference on Advanced Materials and Nanotechnology. ⇑ Corresponding author. E-mail address: ektasharmaphy@gmail.com (E. Sharma). Materials Today: Proceedings xxx (xxxx) xxx Contents lists available at ScienceDirect Materials Today: Proceedings journal homepage: www.elsevier.com/locate/matpr Please cite this article as: E. Sharma and P. Sharma, Applicability of different models of energy bandgap and refractive index for chalcogenide thin films, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2020.01.342