A Direct Comparison of the Kelvin and Electron Beam Methods of Contact Potential Measurement

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Abstract
Comparison of contact potential values determined for a given pair of surfaces by (1) the Kelvin method, which is insensitive to patch fields, and (2) the electron beam method which is, according to patch theory, sensitive to these fields, offers a means of testing the validity of the theory and of determining the extent to which patch effects influence electron beam measurements. A technique for carrying out such comparative measurements in a single sealed-off tube is described. Barium and silver are selected for the study because of the known reproducibility and long-period constancy of their work functions. The measured surfaces are prepared by fractional distillation following intensive outgassing and the technique allows repetitive checking through renewal of these surfaces. Special attention is given to the conditions required for satisfactory Kelvin measurements in all-glass, sealed-off systems.

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