Electrochemical Deposition of Mo-Se Thin Films

Abstract

Semiconductors based on selenium are an important class of semiconducting systems which have been widely studied due to their electronic and optical properties. Among them the special attention is focused on molybdenum-selenium system now. The molybdenum chalcogenides are potential electrode materials for photovoltaic and photoelectrochemical applications due to their light absorbing properties in the visible region. Moreover this material has also been used as a catalyst for hydrogen evolution reaction instead of expensive platinum. Usually, thin films of these materials are prepared by high temperature and vacuum techniques. However electrodeposition has been found to be a very good and low-cost method to fabricate thin films of these compounds.The electrodeposition of thin films of Mo-Se phases from aqueous baths were studied. The effect of different concentrations of selenious acid, sodium molybdate, pH and temperature were examined. Additionally different complexing agents embracing ammonia and citrate were tested. A conventional three-electrode cell: Pt-sheet as counter electrode and Saturated Calomel Electrode (SCE) or Ag/AgCl as reference electrodes were used. The different substrates were used as working electrode: gold, copper and ITO.Electrodeposition mechanism and kinetics of Mo-Se system deposition were studied by the conventional electrochemical methods. Chronoamperometry and cyclic voltammetry techniques were combined with electrochemical quartz crystal microbalance to analyze this process in details. According to the obtained results the potentiostatic conditions were applied to deposit Mo-Se thin-films. The proper adjustment of the process of electrolysis has a crucial role on the composition and structure of the deposited films, which decide about their properties. The applied potential of electrolysis were changed systematically in ranges within which it significantly effects on the composition and structure of the Mo-Se thin films. The composition and the structure of the deposited thin films were identified by XRF, EDS, XRD and grazing incidence XRD techniques. Moreover the morphology of the samples were analyzed by SEM.This work was supported by the Polish National Center of Science under grants 2011/01/D/ST5/05743, 2011/01/N/ST5/05509 and AGH University of Science and Technology contract no. 11.11.180.509.