Contact charge transfer between inorganic dielectric solids of different surface roughness

We measured contact charge transfer between chemically identical, dielectric solids with different surface roughness. Glass of four different roughness levels had its own charge transfer series with the rougher glass negative with respect to the smoother in all combinations. Unpolished N-type silicon wafers became negative to polished N-type wafers; P-type wafers showed the opposite behavior. Rougher glass was more negative than smoother glass after contact with chemically non-identical samples. The results are consistent with modeling studies that show that the concentration of excited electrons is lower in solids in which there is greater access to surface de-excitation.