Influence of substrate temperature on the structural, morphological, optical and electrical properties of copper telluride thin films prepared by electron beam evaporation method P.V. Bhuvaneswari a , K. Ramamurthi b, ⁎, R. Ramesh Babu a a Crystal Growth and Thin Film Laboratory, Department of Physics, Bharathidasan University, Tiruchirappalli 620024, Tamil Nadu, India b Crystal Growth and Thin Film Laboratory, Department of Physics and Nanotechnology, Faculty of Engineering and Technology, Sri Ramaswamy Memorial University, Kattankulathur 603203, Tamil Nadu, India abstract article info Article history: Received 23 February 2016 Received in revised form 29 March 2017 Accepted 13 April 2017 Available online 23 April 2017 Copper telluride thin films were deposited on the glass substrates at different substrate temperatures viz., Room Temperature, 200, 300, 400 and 500 °C employing electron beam evaporation method. The effect of substrate temperature on the physical properties of copper telluride films was investigated. The X-ray diffraction pattern revealed that the films deposited at 300, 400 and 500 °C are polycrystalline in nature. The crystallite size, dislo- cation density and microstrain of these films were evaluated. Scanning electron microscopy images showed that the surface morphology of the films is modified by the variation in the substrate temperature. Further variation in the shape, size and distribution of the agglomerated crystallites formed on the surface of the copper telluride films and the roughness of the films were studied as a function of deposition temperature using atomic force mi- croscopy. The direct optical band gap value of copper telluride films varies from 2.45 to 2.93 eV with variation in the substrate temperature. Positive sign of the Hall coefficient showed p-type conductivity. The copper telluride film deposited at 500 °C showed relatively low resistivity of 1.36 × 10 -3 Ω cm. © 2017 Elsevier B.V. All rights reserved. Keywords: Copper telluride Thin films Electron beam evaporation Structural properties Optical properties Electrical properties 1. Introduction Copper based chalcogenides have been subjected to various investi- gations due to their potential applications in solar cells, batteries, photo- detectors, superionic conductors, photothermal conversion, electro conductive electrodes and microwave shield coatings. Copper telluride belongs to one of the important p-type I–VI compound semiconductors. Reports show that copper telluride exists in various stoichiometric (CuTe, Cu 2 Te, Cu 3 Te 4 , Cu 4 Te, Cu 7 Te 5 , Cu 7 Te 4 ) and non-stoichiometric (Cu 2-x Te, and Cu 1.4 Te) compositions with different crystallographic structures which facilitate to tune their various properties by adjusting the Cu:Te ratio. Thus a wide range of structural diversity of transition metals is occurring due to the partially filled d-shell which allows them to adopt multiple oxidation states [1]. Park et al. [2] used CuTe as the back contact layer in the CdTe solar cells. Han et al. [3] reported that the copper telluride nanostructures such as Cu 2-x Te nanosheets, hollow Cu 2-x Te nanoparticles and Cu 1.67 Te nanocubes are the potential anode materials in rechargeable lithium batteries due to their excellent cycling stability. A large variety of preparation techniques such as elec- trodeposition [4], modified chemical bath [5], aerosol assisted chemical vapour [6], magnetron sputtering [7], pulsed laser [8], thermal evaporation [9–12] and flash evaporation [13] methods were employed to deposit copper telluride thin films. The properties of the prepared films depend on many factors such as film thickness, substrate temper- ature and deposition rate. Ferizovic and Munoz [7] coated the copper telluride thin films at Room Temperature (RT) by magnetron sputtering method and studied their properties as a function of annealing temper- atures. They observed that the films annealed at temperatures from 200 to 400 °C exhibit mixed phases whereas the film annealed at 500 °C shows Cu 2 Te phase. Neyvasagam et al. [9] investigated the optical prop- erties of CuTe thin films (30–150 nm thickness) prepared at 300 K by thermal evaporation method. de Moure-Flores et al. [8] reported the in- fluence of the substrate temperatures (RT, 100, 200, and 300 °C) on the properties of Cu x Te films deposited by pulsed laser deposition method. Among the various deposition parameters the substrate temperature influences the properties of copper telluride film. Hence in the present work we report the effect of substrate temperature (RT, 200, 300, 400 and 500 °C) on the structural, morphological, optical and electrical properties of copper telluride films deposited by electron beam evapo- ration method. 2. Experimental Copper telluride films were deposited on the well cleaned micro- scope glass slides by electron beam evaporation technique using a 12″ Thin Solid Films 632 (2017) 44–49 ⁎ Corresponding author. E-mail address: ramamurthi.k@ktr.srmuniv.ac.in (K. Ramamurthi). http://dx.doi.org/10.1016/j.tsf.2017.04.035 0040-6090/© 2017 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Thin Solid Films journal homepage: www.elsevier.com/locate/tsf