Gasochromic mechanism in a-WO3 thin films based on Raman spectroscopic studies

The gasochromic mechanism in amorphous tungsten oxide films has been invest igated using Raman scattering measurements. The Raman spectra of as-deposit ed films show two strong peaks at 770 and 950 cm(-1) due to vibrations of t he O-W6+-O and W6+=O bonds, respectively. When the Pd/a-WO3 films are gasoc hromically colored by exposure to diluted hydrogen gas, extra Raman peaks d ue to O-W5+-O and W5+=O bonds appear at 330 and 450 cm(-1), respectively. T he Raman spectra of a-WO3 films bleached with isotopic heavy oxygen (O-18) show that the gasochromic coloration in a-WO3 films is directly related to the double injection of hydrogen ions and electrons. (C) 2000 American Inst itute of Physics. [S0021-8979(00)04517-5].