THERMAL-ACTIVATION ENERGY OF SILVER IN ION-EXCHANGED SODA-LIME GLASS INVESTIGATED BY X-RAY PHOTOELECTRON-SPECTROSCOPY

The thermal effect on silver in ion-exchanged glasses was investigated in situ by X-ray photoelectron spectroscopy (XPS) in an ultra-high va cuum environment. Each XPS signal of Ag 3d(3/2) and 3d(5/2) consists o f two components, the metallic state (Ag-0) and the oxidized state (Ag +), resolved after curve fitting. The toward-surface diffusion of silv er was observed by monitoring the changes in concentration on the surf ace during sample annealing between 20 and 450 degrees C. Judging from the variations in line shape and binding energy and from the enhancem ent of surface silver under annealing, both metallic and oxidized silv er are accumulated on the surface. By applying the diffusion theory in a semiinfinite system to the experimental data, the thermal activatio n energy of the oxidized silver in ion-exchanged glass, 0.16 eV, was e stimated. The activation energy of metallic Ag precipitated during hea ting, 0.23 eV, was estimated as well. (C) 1997 Elsevier Science S.A.