Surface resistivity of uncoated insulators

Contact-electrode surface probes measure surface resistivity and have found widespread acceptance in the semiconductor industry and are now becoming a tool in nanotechnology. In the past, the measurement of the surface resistivity of uncoated insulator materials has suffered from poor repeatability within a sample and, even worse, results between laboratories can vary by over an order of magnitude. The recent introduction of the alternating polarity method of measurement, which gives repeatability to within a few percent, solved the former problem. However, the latter problem has led the present author to reexamine the theory of surface resistivity as it applies to uncoated insulator materials in an attempt to explain this widespread variation of surface resistivity data between laboratories. Based on this examination it is proposed that the surface resistivity of uncoated insulators is nothing more than a measure of the amount of water adsorption on the insulator surface. It is argued that the relative humidity, temperature and especially the adsorption equilibrium of oxide pollutants and other salts in the local atmosphere are all responsible for the disparity in surface resistivity measurements between laboratories.