Effects of Substrate Temperature on Electrochromic Properties of Cobalt Oxide and Oxyhydroxide Thin Films Prepared by Reactive Sputtering Using O_2 and H_2O Gases

摘要

Cobalt oxide and oxyhydroxide thin films were prepared by reactive sputtering of a Co target in O_2 and H_2O gases at substrate temperatures from -20 to +200℃. CO_3O_4 films were formed at all the substrate temperatures in O_2 gas and at 200 ℃ in H_2O gas, and amorphous CoOOH films were formed in the range from 10 to -20℃ in H_2O gas. A large transmittance change of approximately 26% and high electrochromic (EC) coloration efficiency of 20cm~2/C at a wavelength of 600nm were obtained for the CoOOH thin films deposited at -20℃ in 0.1 M KOH aqueous solution. The good EC performance of the CoOOH film is attributed to the low film density and amorphous structure.