Preparation and Electrochromic Properties of RF-Sputtered NiO_x Films Prepared in Ar/O₂/H₂ Atmosphere

Abstract

The preparation of electrochromic nickel oxide ( NiO x ) films, which are colorless in an as-deposited state, has been carried out in Ar/O 2 /H 2 mixed gas by the rf-sputtering method. Highly transparent films of as-deposited nickel oxide could be prepared in the sputtering atmosphere consisting of Ar:O 2 :H 2 =50:10:40. From IR and XPS measurements, the as-deposited films were found to be hydrated and to have the component of Ni(OH) 2 . When these films were electrochemically colored, NiOOH was known to remain in the films. The coloration efficiency of the films at the wavelength of 633 nm was nearly independent of hydrogen content in sputtering atmosphere up to 40%, but it depended on sputtering pressure. The maximum value of coloration efficiency was 36 cm 2 /C for films prepared at hydrogen content of 40% and total pressure of 8 Pa.