Preparation of manganese oxide thin films by electrolysis/chemical deposition and electrochromism

Manganese oxide (MnOx) thin films were deposited onto transparent and conductive tin oxide-coated glass substrates by electrochemical deposition (at 1.2 V vs. Ag/AgCl) and subsequent chemical [electrolysis/chemical (EL/C)] processing in a manganese ammine complex solution at pH 8. Characterization by X-ray diffraction (XRD) of the films revealed that the crystal structure formed in the films by EL/C deposition is assigned to gamma -Mn2O3 and/or Mn3O4. X-ray photoelectron spectroscopy (XPS) was also performed to focus on exchange splitting effect shown in Mn 3s spectra and peak analyses of O ls spectra of the films. From electrochemical quartz crystal microbalance, XRD, XPS, and atomic force microscopic studies, a mechanism of film growth was illustrated, featuring time course of rest potential during chemical process. The XPS data also suggested that the electrochromic behavior, turning brown and light yellow by the anodic and cathodic polarization in potassium borate buffer solution at pH 10, originates from a transformation between two oxygen groups in hydroxide (Mn-O-H) and oxide (Mn-O-Mn) accompanied by the change in valence of Mn. The repeated EC switching performance of the films was also assayed. (C) 2001 The Electrochemical Society. [DOI: 10.1149/1.1376637] All rights reserved.