Authors: Miki Ueda Masami Tsukamoto Akira Sakai Shinjiro Okada
Publish Date: 2014/06/05
Volume: 18, Issue: 9, Pages: 2637-2645
Abstract
We investigated the penetration depth profiles of lithium ions in titanium oxide thin film during electrochromic reactions The penetration depth profiles were obtained using timeofflight secondary ion mass spectrometry TOFSIMS for various states associated with coloring and bleaching reactionsIt was found that the amount of penetrated lithium ions in the coloring process decreased sharply with increasing depth for samples in which lithium ions were inserted by applying a voltage Vi for 50 s in electrolyte Over 70 of the total lithium ions were detected within 10 nm from the surface of the film The amount of ions in each depth was represented as a function of 1/d 2 d depth and the penetration depth of the lithium ions increased by increasing Vi Furthermore we found that the deintercalation of the lithium ions by applying a reverse voltage arise preferentially near the surface of the film The deintercalated released lithium ion ratio seems to decrease with increasing the penetration depthHence we expected that an electrochromic device using nanorodstructured titanium oxide film would improve reproducibility owing to a small number of unreleased ions A film composed of nanorods was made by oblique evaporation The electrochromic device using the nanorodstructured film showed excellent reproducibility for small value of driving voltage The number of possible switching increased by a factor of 30 according to the driving voltage
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