Maxwell stresses at charged metal surfaces from thin-film elastoresistance

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Abstract
Thin metal films, when charged electrostatically, show a change of electrical conductance quadratic in the applied surface-charge density. The sign and magnitude of this signal, as well as its sensitivity to mechanical constraints of the sample, are compared to a model based on the elastoresistive response of the metal film to the Maxwell stresses accompanying electrostatic charging. The agreement for Ag, Au, Cu, Al, and Sb on mica is satisfactory. Apart from elucidating one of the basic electrical responses of metals to charging, the effect lends itself to studying the mechanical constraints imposed on metal films by the metal-substrate coupling, and by external surface layers. Some examples of such interactions are discussed.