ELECTRON MICROSCOPE OBSERVATION OF ATOMIC PLANES AND ATOMIC POSITIONS IN GERMANIUM

Abstract

One factor limiting the resolution of crystal lattice planes in the electron microscope is hydrocarbon contamination of the specimen during observation. This problem was minimized by rebuilding the Siemens Elmiskop 1 vacuum system. With the new system the best operating vacuum attainable in the microscope was improved from 1 × 10⁻⁵ Torr to 1.2 × 10⁻⁷ Torr. The corresponding contamination rate was reduced from 2 Å/second to 0.1 Å/second. Using this vacuum system and operating the microscope at 100 kV with pointed filaments, both single and crossed lattice images of atomic planes in germanium were obtained. Single lattice images were obtained in which the 3.26 Å spacing of the (111) planes was resolved. Atomic positions were revealed in the crossed lattice images by the intersection of two sets of (111) planes and one set of (200) planes of spacing 2.83 Å.