Structure-property relationships in electrochromic WO3 films deposited by reactive sputtering

WOx electrochromic (EC) films deposited by DC magnetron sputtering technique were investigated by XRD and STM measurements. The reversible microstructure changes of the WOx film between the bleached and colored EC states were revealed. The study indicates that the amorphous as-deposited WOx film (a-WOx) is of amorphous microstructure both in bleached and colored states; however, the crystalline WOx (c-WOx) is stoichiometric triclinic lattice WOx in bleached state (the lattice parameters: a = 7.2944 Angstrom, b = 7.4855 Angstrom, c = 3.7958 Angstrom, alpha = 89.38 degrees, beta = 90.42 degrees gamma = 90.80 degrees), and changes into nonstoichiometric tetragonal lattice WO2.9 in colored state (a = b = 5.336 Angstrom, c = 3.788 Angstrom, alpha = beta = gamma = 90 degrees). The surface morphologies of the colored WOx films are very different from those of the bleached WOx films. (C) 2000 Published by Elsevier Science B.V. All rights reserved.