Scanning volta potentials and polarization measurements of metals in irradiated air

A method for direct dc measurement of the Volta potential is presented. A h igh intensity synchrotron X-ray beam 20 mu m in diam was used to locally ir radiate the atmosphere adjacent to the metal surface and produce a conducti ng path between a sample and a reference probe. The direct measurements of potential compared favorably with traditional Kelvin probe measurements. Th e direct measurements have a poorer spatial resolution but the measurements could be made at probe heights of around 1 mm compared to less than 0.1 mm for the Kelvin probe. In contrast to the Kelvin probe methods, the approac h described allows observation of the current as a function of impressed vo ltage. Hence, it can be used as an active probe for electrochemical measure ments in the gaseous phase. (C) 2000 The Electrochemical Society. S1099-006 2(00)01-005-1. All rights reserved.