Manganese oxide thin film preparation by potentiostatic electrolyses and electrochromism

Manganese oxide (MnOx) thin films were deposited on transparent conducting tin oxide glass substrates by potentiostatic anodic electrolysis of alkaline solution of a manganese ammine complex at 298 K. The effects of varying deposition potentials on the microstructure and the electrochromic (EC) properties of the films were investigated. Characterization of films by X-ray diffraction revealed that two distinct potential regions (lower and higher than 0.3 V vs. Ag/AgCl) were available for the film deposition; the crystal structure of the film deposited at lower and higher regions were gamma-Mn2O3 and/or Mn3O4 and Mn7O13. 5H(2)O respectively. X-ray photoelectron spectroscopy (XPS) analyses of the films featuring exchange splitting effect on Mn 3s spectra indicated that the valence of manganese in the films prepared at lower and higher potential regions are mixtures of divalence-trivalence and of trivalence-tetravalence, respectively. The XPS analysis also revealed that terminal chemical bonding species of the films are a mixture of hydroxide (Mn-O-H) and oxide (Mn-O-Mn). The mechanism of the EC process, by which the color change between brown and light yellow occurs, could be explained in terms of the transformation between these two oxygen groups in Mn-O-H and Mn-O-Mn, accompanied by the change in valence of Mn. The EC durability of the films in switching performance was also assessed. (C) 2000 The Electrochemical Society. S0013-4651 (99)08-027-1. All rights reserved.