SURFACE EFFECTS ON THE ELECTRODIFFUSION OF ALKALI-METAL IONS AND PROTONS IN QUARTZ

The influence of the surface on the electromigration of alkali-metal ions or protons acting as charge compensators of trivalent impurity centers in quartz is determined on the basis of potential surface calculations. Proton compensator migration depends on the ability for proton penetration at the anode interface. The ionic current density depends on the ability for alkali-metal ions to escape at the cathode interface. A study of the potential energy experienced by the diffusive ion during its migration through the quartz surface and onto the surface plane allows us to determine the diffusion path and to calculate the jump frequencies of the surface potential for Li+, Na+, and H+. The penetration and escape processes are shown to be preponderant for the evaluation of the ionic current density in the electromigration mechanism.