SEM-visualization of a spatial charge and a giant potassium peak in a corona-poled glass.

We visualized a region of a spatial electric charge in a corona-poled soda-lime glass using scanning electron microscopy (SEM). The SEM image obtained perfectly coincides with a numerically calculated distribution of the spatial charge in the structure. Compositional depth profiles of the glass were characterized with energy dispersive X-ray (EDX) analysis. The measurements showed that K+ ions, the total concentration of which in pristine glass is practically negligible, pile-up significantly just beside a backfront of fast Na+ ions, and their peak concentration exceeds initial K+ content by about 15 times. This is in a good agreement with an analytical model recently presented by R. Oven. However, diffusion smearing of the spatial charge distribution and the poling profiles turns out to be much larger than the theory predicts.