American Journal of Chemistry and Materials Science 2014; 1(2): 11-17 Published online September 20, 2014 (http://www.openscienceonline.com/journal/ajcms) Room temperature two-step synthesis of cadmium telluride films Magdalena Osial 1 , Justyna Widera 2, * , Krystyna Jackowska 1 1 Laboratory of Electrochemistry, Department of Chemistry, University of Warsaw, Pasteur 1, 02-093 Warsaw, Poland 2 Department of Chemistry, Adelphi University, 1 South Avenue, NY 11530 Garden City, United States Email address magdalena@osial.edu (M. Osial), widera@adelphi.edu (J. Widera), kryjacko@chem.uw.edu.pl (K. Jackowska) To cite this article Magdalena Osial, Justyna Widera, Krystyna Jackowska. Room Temperature Two-Step Synthesis of Cadmium Telluride Films. American Journal of Chemistry and Materials Science. Vol. 1, No. 2, 2014, pp. 11-17. Abstract CdTe films were prepared at room temperature by using two-step method. In the first step, Cd layer was deposited electrochemically on Pt substrate and in the second step, CdTe films were formed chemically by dipping substrate covered with Cd into the solution containing telluride ions. The properties of deposited CdTe films were investigated. Using XRD method, it was found that the formed CdTe films are polycrystalline with cubic structure. Raman and XPS spectra revealed that deposits contain not only CdTe but also some amount of TeO 2 and probably CdO or Cd(OH) 2 , as well. The optical band gap energy determined using UV-Vis spectra was in the range of 1.4-1.6 eV depending on the length of time of Cd deposition. The changes in deposited films photoactivity under illumination in the telluride solution indicated the formation of n-type of CdTe films. Keywords Cadmium Telluride, Thin Films, Two-Step Method, Crystallinity, Chemical Composition, Morphology 1. Introduction There is a considerable interest in the low cost deposition methods for formation of thin semiconducting films because of their potential application in photovoltaics, optoelectronic, thermoelectric devices, solar energy convertors, detectors and sensors. Among many semiconductors, cadmium telluride (CdTe) is one of the most promising materials for the heterojunction photovoltaic devices. It is characterized by a large absorption coefficient (> 10 4 cm -1 ) and a low energy band gap (1.44 eV) providing an optimal match with the solar spectrum. Thin CdTe films can be prepared by using various techniques such as: vacuum sublimation [1] molecular beam epitaxy [2], chemical vapour deposition [3], spray pyrolysis [4], chemical bath deposition (CBD) [5] and electrodeposition [6-12]. All these methods are one-step methods and most of them are carried out at higher temperatures. Even CBD and electrochemical formation of CdTe should be performed at about 70 ⁰ C as the solubility of telluride compounds is very low. However, there are also two-step methods of CdX (X: -S, -Se) formation that can be applied at ambient temperature. These methods called SILAR or ILGAR are based mostly on the adsorption of cadmium ions on the substrate followed by a chemical reaction of adsorbed metal ions with chalcogen ions present in solution or in gas phase [13-15]. The other two-step method, called, hybrid electrochemical/chemical method was applied by R.M. Penner et al. for the formation of CdS and CdI nanocrystals [16-18]. In this method, the Cd was first electrodeposited on a substrate and after Cd oxide or hydroxide formation it was transformed chemically into a proper salt. Such electrochemical/chemical methods have been used by C.D. Lokhande et al. [19] for the preparation of CdSe films from acidic solution containing selenide oxide (IV). In this paper, we report the application of an electrochemical/chemical method for the preparation of cadmium telluride films. The applied method consists of two steps: 1) electrodeposition of Cd and 2) its subsequent chemical conversion into CdTe by dipping the deposited Cd layer in 3M NaOH and subsequently in basic solution