Color change mechanism of niobium oxide thin film with incidental light angle and applied voltage

Publication date: Available online 9 February 2016
Source:Thin Solid Films
Author(s): Isao Komatsu, Hayata Aoki, Mizue Ebisawa, Akihiro Kuroda, Koichi Kuroda, Shuichi Maeda
Niobium oxide thin layers made by the anodization process showed coloration owing to thin film interference. The reflection spectra depended on both the applied voltage and incident light angle. Large color differences were observed at incident light angles between 5° and 70°, when the applied voltage was over 60 V. In this study, we explored the cause of these results using ellipsometry and goniophotometry to understand the transition of optical constants and the reflection spectra with applied voltage. Finally, we concluded that the coloration of reflection spectra, which included only a first-order interference peak, exhibits a smaller change because the first order interference peak has a wider half value width than higher order interference peaks.