JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS, cilt.45, ss.7780-7783, 2006 (SCI-Expanded)
Thin films of Ni oxide were deposited by reactive sputtering in argon/oxygen gas mixtures using O-2 flow concentrations ranging from 6 to 100% and their electrochemical and electrochromic properties were examined using dilute acidic (1 M KCl + 0.5 mM H2SO4) and basic (1 M KOH) aqueous electrolyte solutions. An electrochromic coloration efficiency of 32 +/- 5 cm(2)/C was obtained for all the Ni oxide films regardless of O-2 concentration in both KCl + H2SO4 and KOH. The charge capacity and resultant change in them optical density of the Ni oxide films increased with O-2 concentration owing to a decrease in crystal grain size and the resultant increase in the active surface area of the NiO crystal grains. Although the interfacial capacitances of the Ni oxide films in KCl + H2SO4 are 2-3 times less than those in KOH, a maximum change in optical density of 0.57 was obtained in KCl + H2SO4 for a fine-grained Ni oxide film with a thickness of 400 ran sputtered in 100% O-2.