Crystallinity and morphology changes of a-WO films

The crystalline property changes of a-WO3 films deposited by reactive sputtering are studied using HREM, STM and other techniques. The results indicate that cyclical electrochemical hydrogen insertion and extraction weakens the amorphous feature and increases the crystalline properties of the as-deposited a-WO3 films. The degree of these changes is strongly correlated with the degree of electrochemical cycling of the a-WO3 film. STM analysis reveals that the morphology of saturated colored a-WO3 films consists of very fine grains ca. 20 nm.with voids in the film, whereas the morphology of unsaturated colored a-WO3 film consists of relatively compact large ca. 110 nm.clusters. H2O compounds are formed in both coloring and bleaching process of the a-WO3 film electrochemical cycles. q1999 Elsevier Science B.V. All rights reserved