Measuring surface roughness of specimen - involves measuring current through broad electrodes in contact with surface

摘要

The specimen is of poorly conducting or insulating material, and an electrode making good contact with it is placed on each of two opposite sides of a sample of the specimen material, and the normal conductivity is measured through these electrodes. An electrode is placed on the specimen side whose surface roughness is to be measured; its contact is poor owing to empty spaces produced by the surface roughness. A well contacting electrode is placed on the opposite surface and conductivity of the speciment is measured by a voltage generating in the specimen an electric field of the order of about 3kV/cm. The reciprocal of the ratio of this reduced conductivity to normal conductivity is taken as a measure of the surface roughness.