Visualisation of the preferential adsorption sites of oxygen onto WO3 nano-particles

摘要

Spatially resolved scanning tunnelling spectroscopy experiments have been performed in ultra high vacuum onto nano-particles of WO3. Samples annealed in vacuum (300 degreesC) show higher conductivity at the necks connecting adjacent particles, where the occurrence of metallic states is favoured. After exposure to oxygen the conductance behaviour is reversed, with the necks becoming less conductive than the particle surface. Re-annealing at 300 degreesC restores the initial conditions. A direct interpretation of the experiments indicates that oxygen is preferentially adsorbed at interstitial regions, where it saturates the metallic states. This observation gives a microscopic rationale to the macroscopic decrease of the conductance observed in WO3 based gas sensors, after the interaction with oxidising gases. (C) 2001 Elsevier Science B.V. All rights reserved. References: 13