|AVS 54th International Symposium|
|Thin Film||Thursday Sessions|
|Session:||Aspects of Thin Films Poster Session|
|Presenter:||H. Sugawara, Aoyama Gakuin University, Japan|
|Authors:||H. Sugawara, Aoyama Gakuin University, Japan
I. Yamamoto, Nissan Motor Co., Ltd., Japan
Y. Sato, Aoyama Gakuin University, Japan
Y. Shigesato, Aoyama Gakuin University, Japan
|Correspondent:||Click to Email|
Electrochromic devices have been expected as the one of the environmental technologies such as architectural "smart" windows which should have large potential to save energy. Ni oxide (NiO) films have been studied extensively as oxidation-coloring materials, which could be used as counter electrode of amorphous WO3 films. Azens, et al. reported that heavy Mg dopings (atomic ratio of Mg/ (Ni+Mg): 44.4 %) on NiO was effective to improve optical transmittance in visible light region of 380-600 nm at the bleached state.1 In this study, we investigated Mg doped Ni oxide films in the wide range of the doping concentration and variation of the electrochromic properties were investigated in detail. Ni oxide flims were deposited on unheated ITO-coated glass substrates by rf magnetron sputtering using NiO-MgO targets with various Mg doping concentrations (atomic ratio of Mg/ (Ni+Mg): 0, 5, 10, 20 %). Ar was used as a sputtering gas and O2 was introduced as a reactive gas (O2 gas composition changes from 0 % to 100 %). Total gas pressure during the depositions was maintained at 5 Pa and the film thickness was adjusted approximately to 200 nm. Crystallinity and surface morphology of the films were analyzed by X-ray diffraction (XRD) and atomic force microscope (AFM), respectively. The composition and the chemical state of the elements were analyzed by X-ray photoelectron spectroscopy (XPS). In order to analyze the electrochromic properties, the specimens were immersed in a 1M KOH electrolyte and underwent voltammetric cycling in a three-electrode arrangement with a Pt counter electrode and an Ag/AgCl reference electrode. The Ni oxide films with the proper amount of Mg doping showed higher coloration efficiency and higher transmittance at the bleached state than Ni oxide films without doping. The optimized doping concentration in this study was 5 % for the highest electrochromic performance.
1 A. Azems, J. Isidorsson, R. Karmhag, C. G. Granqvist, Thin Solid Films, 422 (2002) 1.