Contents lists available at ScienceDirect Materials Science in Semiconductor Processing journal homepage: www.elsevier.com/locate/mssp Nanocrystalline Zn x Te 100-x (x = 0, 5, 20, 30, 40, 50) thin films: Structural, optical and electrical properties Harinder Singh a , Palwinder Singh b,c , Anup Thakur b , Tejbir Singh d , Jeewan Sharma a, ⁎ a Department of Nanotechnology, Sri Guru Granth Sahib World University, Fatehgarh Sahib 140 407, India b Department of Basic and Applied Sciences, Punjabi University Patiala, Punjab 147 002, India c Department of Physics, Punjabi University, Patiala 147 002, India d Department of Physics, Sri Guru Granth Sahib World University, Fatehgarh Sahib 140 407, India ARTICLE INFO Keywords: Thermal evaporation Optical band gap Thin films Tauc's plot Melt quenching ABSTRACT In the present paper, the structural, optical and electrical properties of nanocrystalline Zn x Te 100-x (x = 0, 5, 20, 30, 40, 50) thin films (average thickness ~ 350 nm), deposited by thermal evaporation, have been studied. The X-ray diffraction results revealed that single phase Zn x Te 100-x was obtained at x = 50. Fourier transform in- frared spectra also revealed the formation of zinc blende phase at x = 50. Energy dispersive X-ray spectroscopy confirms the elemental composition. Field emission scanning electron micrographs confirmed the uniform de- position of all thin films. UV–Vis–NIR results revealed that the optical band gap, calculated by Tauc's plots, increases with increase in Zn content. This may be due to the alloying effect. Temperature dependent dark conductivity showed that conductivity is thermally activated process having single activation energy in the measured temperature range (300–375 K). The dark conductivity and activation energy decreased with increase in Zn content. The explanations of variation in the properties of ZnTe with increase in Zn percentage have been provided. 1. Introduction In recent years, II–VI group chalcogenide materials have attracted great attention of scientists around the globe because of their wide range applications as solid-state devices both in technological and sci- entific field [1]. Moreover, these materials are economically viable for the production of low cost photovoltaic devices [2]. This group semi- conductors (such as ZnO, ZnS, ZnSe, ZnTe, CdO, CdS, CdSe, and CdTe) have direct and wide band gap due to which these are widely used in the fabrication of solar cells and optoelectronic devices [3,4]. Among them ZnTe is one of the exciting semiconductor material with optimum band gap (~ 2.26 eV at room temperature) [5] and low electron affinity (3.53 eV) [6]. It is usually a p-type semiconductor [7] with cubic [8] or hexagonal structure that depends upon the synthesis conditions [9]. Such parameters make it useful in design of green LEDs [10], IR de- tectors [11], high efficient powder-phosphor screens [12], THz emitters [13], detectors [14], opto-refractive materials for non-polarized memory switching and optical data processing ray detectors [15,16]. ZnTe is also used as a back contact layer in CdTe based solar cells. It provides higher efficiency in these solar cells due to small valence band offset of 0.1 eV between ZnTe and CdTe [17]. These applications are closely related to variation in optical and structural properties of ZnTe thin films [6]. To the present, various methods such as, RF sputtering [18], electro deposition [19], thermal evaporation [20], DC sputtering [21], vapour phase epitaxy [22], closed space sublimation [23], molecular beam epitaxy [24], magnetron sputtering [25], electrochemical process [26], metal organic vapour phase epitaxy (MOVPE) and metal organic che- mical vapour deposition (MOCVD) [27] have been used to synthesize ZnTe thin films. Among these methods, thermal evaporation technique provides thin films on large area and gives better control of deposition rate, film thickness and temperature [28]. Various research groups [29–32] have reported the study on optical, structural and electrical properties of ZnTe thin films. However, the compositional dependent study on structural, optical and electrical properties of ZnTe thin films has been limitedly reported. Kishore et al. [33] has studied the structural and thermal transport properties of Zn x Te 100-x (x = 5, 10, 30 and 50) alloys in pellet form. They reported that the diffraction results of Zn 50 Te 50 composition show the presence of both Te and ZnTe phases. Sharma et al. [34] prepared the Zn x Te 100-x (x = 5, 10, 30 and 50) pellets of 99.99% purity and reported the XRD result for Zn 5 Te 95 . Hexagonal Te exhibits most diffraction peaks as compare to cubic ZnTe. The workers used reflection spectroscopic technique to investigate the optical properties of these pellets. They https://doi.org/10.1016/j.mssp.2017.12.002 Received 21 September 2017; Received in revised form 21 November 2017; Accepted 1 December 2017 ⁎ Corresponding author. E-mail address: jeewansharma29@gmail.com (J. Sharma). Materials Science in Semiconductor Processing 75 (2018) 276–282 1369-8001/ © 2017 Elsevier Ltd. All rights reserved. T