Electrochemistry of MnO x electrodes has been widely studied as originated from their application for active materials in primary batteries, typically preparation of MnO 2 electrode by galvanostatic electrolysis has been performed. 1 Furthermore, MnO x thin films have received much attention as electrochromic (EC) materials. 2,3 Several preparation methods of EC MnO x thin films including galvanostatic electrolysis, 4,5 chemical vapor deposition, 6 thermal decomposition, 7 and electron beam evaporation 8 have been proposed. Previously, we have prepared nickel oxide (NiO x ) thin films by potentiostatic anodic electrolysis of slightly alkaline (pH 9) solutions of nickel ammine complex [Ni(NH 3 ) x 2ϩ ], 9,10 demonstrating a potential-selective deposition behavior in which thin films of ␣-Ni(OH) 2 and ␤-NiOOH were produced, respectively, in the two separate potential regions.In light of our previous study, we have applied a similar method for preparation of MnO x thin films. The potential-pH diagram for a manganese-water system shown by Pourbaix 11 indicates several thermodynamically stable manganese oxides such as Mn 3 O 4 , Mn 2 O 3 , and MnO 2 containing divalent, trivalent, and tetravalent manganese, respectively, in alkaline phase, from which one may expect potentialselective preparation of MnO x thin films. This paper reports the first preparation of MnO x thin films via potentiostatic electrolysis and compares the EC characteristics of the films.

The p-type semiconductor cuprous oxide ͑Cu 2 O͒ film has been of considerable interest as a component of solar cells and photodiodes due to its bandgap energy of 2.1 eV and high optical absorption coefficient. We prepared Cu 2 O films on a conductive substrate by electrodeposition at 318 K from an aqueous solution containing copper sulfate and lactic acid. The structural and electrical characterizations of the resulting films were examined by X-ray diffraction, X-ray photoelectron spectroscopy, and X-ray absorption measurements, and the Hall effect measurement, respectively. The resistivity varied from 2.7 ϫ 10 4 to 3.3 ϫ 10 6 ⍀ cm, while the carrier density was from 10 12 to 10 14 cm −3 and the mobility from 0.4 to 1.8 cm 2 V −1 s −1 , depending on the preparation conditions, i.e., solution pH and deposition potential. The carrier density was sensitive to the atomic ratio of Cu to O in the films and the mobility to the grain size.

Manganese oxide false(MnOxfalse) 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 γ­Mn2O3 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 1s spectra of the films. From electrochemical, quartz crystal microbalance, XRD, XPS, and atomic force microscope 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. © 2001 The Electrochemical Society. All rights reserved.

The direct electrodeposition of Ag2O films was discovered for the first time using a new strategy termed “oxides synthesis induced by electrogenerated acid”. The Ag2O film with a bandgap energy of 1.46 eV is suited to a light absorption layer in photovoltaic cells.