The development of Fresnel contrast analysis, and the interpretation of mean inner potential profiles at interfaces

This paper provides a summary of recent published and unpublished research on the development of Fresnel contrast analysis, a transmission electron microscopy technique for measuring the mean inner potential profile across an interface or a narrow layer. An algorithm for finding a best-fitting potential profile is described, energy-filtered experimental data are analyzed and contributions to Fresnel contrast from surface grooves and space charge are assessed. Many of the conclusions drawn are equally relevant for the interpretation of phases measured using off-axis electron holography.