The refractive index of sodium silicate glass can be easily modified by the ion exchange technique. Silver is commonly used to replace sodium in order to fabricate the planar waveguide. However, the thermal stability of silver in glass is a major concern of the device performance. The X-ray Photoelectron Spectroscopy was used in an attempt to study the thermal diffusion behavior of silver in soda-lime glasses during heat treatment in ultra-high vacuum. The temperature dependent concentration changes and oxidation states of Ag were monitored in situ inside the ultra-high vacuum chamber. The results show that silver diffused toward surface during the heating and two chemical states of Ag, neutral and oxidized, were observed during heating and cooling processes. It was also observed that the Ag diffusion started at 100 °C and that the neutral Ag accumulated on the surface with greater rate than oxidized Ag until 450 °C. The oxidized Ag increases while the neutral Ag decreases during cooling process. The thermal effect on ion-exchanged glass and the conversion between oxidized and neutral Ag were discussed.
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