Influence of substrate temperature on structural and optical properties of bismuth oxide thin films deposited by close- spaced vacuum sublimation M.M. Ivashchenko a, * , I.P. Buryk a , V.M. Latyshev b , A.O. Stepanenko b , K.S. Levchenko a a Konotop Institute, Sumy State University, 24, Myru Ave., Konotop, UA, 41600, Ukraine b Sumy State University, 2, Rimsky-Korsakov Str., Sumy, UA, 40007, Ukraine article info Article history: Received 14 October 2015 Accepted 15 October 2015 Available online 20 October 2015 Keywords: Bi 2 O 3 Optical study Tauc plot SEM TEM FTIR abstract Bi 2 O 3 thin films were deposited on ultrasonically-cleaned glass and mica substrates by close-spaced vacuum sublimation technique. Films surface morphology was studied using scanning electron microscopy (SEM). Structural study based on the transmission-electron microscopy (TEM) and selected-area electron diffraction (SAED) analysis has been shown that deposited films were polycrystalline with face-centered cubic structure. Optical study was carried out by spectral photometry analysis in the wavelengths range l ¼ 320e900 nm using the optical transmittance and absorbance measurements. For determination optical band gap E g the Tauc plot was used and the band gap energy E g is determined in the range of 3.50e3.62 eV, respectively. Fourier-transform infra-red (FTIR) analysis shown that ob- tained films are well-crystalline and have a good optical quality. © 2015 Elsevier Ltd. All rights reserved. 1. Introduction Bismuth trioxide (Bi 2 O 3 ) is a semiconductor compound which has an attracted attention due to its unique properties such as: large band gap value (from 2.00 to 3.96 eV) [1], high refractive index and dielectric permittivity [2], remarkable photo- sensitivity and photoluminescence [3], etc. This material taking into account the previously mentioned features is promising for the development of various solid state technologies, such as: gas sensors [4], optical coatings [5], biosensors [6], photovoltaic cells [7], etc. Bismuth trioxide has four polymorph modifications: a, b, g, and d [8]. The monoclinic a-Bi 2 O 3 phase is thermodynamically stable at temperature below 1002 K. This modification transforms to the face-centered cubic (fcc) d-Bi 2 O 3 phase above 1003 K and will remain stable to the 1098 K. Another compounds modifications (tetragonal b-Bi 2 O 3 and cubic g-Bi 2 O 3 ) are meta- stable and formed upon cooling from the melt [9,10]. Bi 2 O 3 thin films have previously been prepared by a various methods, such as: reactive magnetron sputtering [2,8,11e 14], atomic layer deposition [9], solegel technique [15], green synthesis [16], chemical vapor deposition [17], pulsed laser deposition [18,19], solution growth [20], fusion-sprayed method [21], electrochemical deposition [7,22], thermal vacuum evaporation with thermal [23] or air [24] oxidation. The variation of the last method e close-spaced vacuum sublimation * Corresponding author. E-mail address: m_ivashchenko@ukr.net (M.M. Ivashchenko). Contents lists available at ScienceDirect Superlattices and Microstructures journal homepage: www.elsevier.com/locate/superlattices http://dx.doi.org/10.1016/j.spmi.2015.10.025 0749-6036/© 2015 Elsevier Ltd. All rights reserved. Superlattices and Microstructures 88 (2015) 600e608