Applications of Electron Holography

Abstract

Electron holography is now at the stage where the emphasis on technique development is slowly shifting towards an emphasis on applications. This is particularly true for electron holography at moderate resolutions, where the phase image gives information about electrostatic and magnetic fields in the sample and in the space around the sample. Such information is not normally available from the intensity images obtained by non-holographic microscopy techniques. This is why most of the published applications of electron holography have been concerned with studies of electromagnetic fields. This book has already devoted Chapter 7 and Chapter 8 to the theoretical and experimental aspects of studying electromagnetic fields by off-axis electron holography. To avoid duplication, in this chapter we will only discuss applications of moderate resolution electron holography to cases when there are no strong electrostatic and/or magnetic fields in the samples. The phase in this case is mainly affected by the mean inner potential and the thickness of the material, with additional contributions from diffraction effects. We will first discuss these three dependencies as a background for the ensuing review of applications of holography to interfaces, surfaces and small particles.