Ionic diffusion of (H_2O)_{n}^{+} and CO¯_3 on SiO_2 surfaces has been quantified using Kelvin force microscopy measurement of ion distribution change after small spot corona charge. For both positive and negative ionic species, the concentration profiles versus time follow the two-dimensional surface diffusion enabling a determination of corresponding diffusion coefficients. On a thermally grown SiO_2 surface, diffusion coefficients of (H_2O)_{n}^{+} and CO¯_3 ions were 2.2 × 10^{-11} cm^2/s and 4.8 × 10^{-12} cm^2/s, respectively. On a chemically cleaned SiO_2 surface, diffusion coefficients of (H_2O)_{n}^{+} and CO¯_3 ions were 7.5 × 10^{-9} cm^2/s and 2.4 × 10^{-9} cm^2/s, respectively. Mathematical analysis of the surface potential decay yields an additional parameter - capacitance equivalent thickness.
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