Phase contrast in TEM can only give information in a limited band of spatial frequencies. The differential phase contrast mode in STEM does not have this limitation, since one simply measures the angle over which the electron beam is deflected by the specimen. This is useful, for example, for determining the magnetic field distribution in magnetic thin films. Recently, a form of electron holography was developed, also in STEM, to obtain differential phase contrast images. In this method, the illuminating beam is split by a biprism in such a way that there are two mutually coherent electron source images close to the specimen. On a far away CCD detector, two shadow images are formed which interfere to give a fringe pattern. It is this fringe pattern that contains the differential phase information. Here, we show that differential phase contrast can also be obtained in a TEM.In the TEM, two coherent illuminating beams are created by a beam splitter in the condenser system. These beams can be treated as two plane waves, creating a fringe pattern in the plane of observation,as shown in figure 1.
A Phase Space Perspective on Electron Holography - Building Bridges Between Inline-, Off-axis Holography, Differential Phase Contrast and Diffractive Imaging