%0 Journal Article
%K Absorptivity
%K Coloration
%K Electrochemical coating
%K Electrochromism
%K Hydroxyl radicals
%K Microstructure
%K Nickel
%K Nickel oxides
%K Sputtering
%K Thin films
%A David A Wruck
%A M.A Dixon
%A Michael D Rubin
%A Susan N Bogy
%B Journal of Vacuum Science Technology A
%D 1991
%G eng
%N 4
%P 2170-2173
%R 10.1116/1.577245
%T As-Sputtered Electrochromic Films of Nickel Oxide
%V 9
%1 <p>Windows and Daylighting Group</p>
%2 LBL-30066
%8 02/1991
%! J. Vac. Sci. Technol. A
%X <p>Electrochromic nickel oxide films were deposited by radio-frequency magnetron sputtering of a Ni target in gas mixtures of Ar and O<sub>2</sub>. When electrochemically cycled in 0.1 N KOH solution, large reversible changes in visible absorption were obtained within the first 10 bleach/color cycles. Films which showed the greatest changes in optical properties and charge capacity were produced within a narrow range of oxygen flow rates. The coloration efficiency was found to be insensitive to the sputtering conditions and stoichiometry, with a value of 34+-4 cm<sup>2</sup>C<sup>-1</sup> at 550 nm. This indicates that microstructure and charge capacity determine the absorption coefficient. The reaction rate was found to depend on the concentration of OH<sup>-</sup> in the electrolyte, indicating that OH<sup>-</sup> diffusion in the electrolyte limits the rate of reaction.</p>