Reflection shadow imaging of crystal surface by low-voltage point-reflection electron microscopy

We present experimental observations of low-voltage point-projection electron microscopy (PPM) in the reflection geometry (point-reflection electron microscopy (PRM)) and their interpretations. The cone of rays originating from an electron-field-emitter tip placed near the surface of a bulk crystal is Bragg reflected, and shadow images of the surface form inside each Bragg-reflected order. Shadow images of the cleaved GaAs (1 0 0) surface were obtained, using electrons of a few hundred volts kinetic energy. They are images of the same surface, projected from different virtual source directions beneath the surface. Reflected line patterns were also observed. Their origins are given, based on results from simulation and three-dimensional electron ray-tracing calculations. The instrument is promising for obtaining simple LEEM-type and stereographic images of crystal surface, since the shadow image in each reflected Bragg disk provides a projection of the surface from a different perspective.