REFLECTION SHADOW IMAGING OF CRYSTAL-SURFACE BY LOW-VOLTAGE POINT-REFLECTION ELECTRON-MICROSCOPY

We present experimental observations of low-voltage point-projection e lectron microscopy (PPM)) in the reflection geometry (point-reflection electron microscopy (PRM) and their interpretations. The cone of rays originating:rom an electron-field-emitter tip placed near the surface of a bulk crystal is Bragg reflected, and shadow images of the surfac e 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 features, pr ojected from different virtual source directions beneath the surface. Reflected line patterns were also observed. Their origins are given, b ased on results from simulation and three-dimensional electron ray-tra cing calculations. The instrument is promising for obtaining simple LE EM-type and stereographic images of crystal surface, since the shadow image in each reflected Bragg disk provides a projection of the surfac e from a different perspective. (C) 1998 Elsevier Science B.V. All rig hts reserved.