Pure phase objects having low spatial frequency such as electromagnetic fields in a vacuum can be visualized by electron holography or three-wave interference.1,2) Wavefront-division interference using a biprism requires a field-emission electron gun having high spatial coherency. On the other hand, amplitude-division interference using a thin crystal does not need high spatial coherency of electron source, i.e. an ordinary electron microscope with a LaB6 filament is good enough to form lattice fringes of high contrast. This is an advantage of amplitude-division interference.3,4)

We previously reported three-wave interference achieved by using two electron biprisms. Recently, we have realized amplitude-division three-wave interference by using a Si crystal as a splitter of an electron wave. Figure 1 shows the experimental set-up used to form an amplitude-division threewave interference pattern. A thin crystal prepared by ion-milling is installed at the standard specimen position, and a thin carbon film on which latex particles are sticking is placed at the selected area aperture position.