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Title: Electrochromic writing and erasing on tungsten oxide films in air by scanning tunneling microscopy
Authors: Qiu, H.
Lu, Y.F. 
Mai, Z.H.
Issue Date: 1-Jan-2002
Citation: Qiu, H., Lu, Y.F., Mai, Z.H. (2002-01-01). Electrochromic writing and erasing on tungsten oxide films in air by scanning tunneling microscopy. Journal of Applied Physics 91 (1) : 440-443. ScholarBank@NUS Repository.
Abstract: The scanning tunneling microscope (STM) was used for both spot coloring and bleaching on α-WO3-x thin films. By wetting the STM tip with 1 M KOH solutions or de-ionized water before the tip approached, and keeping the humidity higher than 40%, the electrochemical reaction occurred at the tip-surface gap while the electrochromic reactions took place at the film surface. With a constant negative sample bias and grounded tip, a brown color circle or a light blue disk was formed on the surface with an enlarged diameter. The circle and disk formations were attributed to the production of alkali and hydrogen tungsten bronzes. By applying a positive sample bias with a grounded tip, the color of the hydrogen tungsten bronze could be bleached. The cathodic reduction of W6+ forms a color center at the W5+ site, while the anodic reaction removes an electron from the color center W5+ state. Raman spectroscopy indicated that for the colored state, the frequency for the W-O bond stretching mode increased, while for the WO bonds it decreased. © 2002 American Institute of Physics.
Source Title: Journal of Applied Physics
ISSN: 00218979
DOI: 10.1063/1.1424053
Appears in Collections:Staff Publications

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