Electron Microscopy at Liquid Helium Temperatures

Abstract

Transmission electron microscopy (TEM), which is potentially capable of providing structural information at very high resolution from crystalline or paracrystalline samples containing as few as 10⁴ unit cells or less, is bringing a new era to crystallography which is of particular interest to microbiologists. Paradoxically, however, the strong interaction of electrons with solids that makes this possible has secondary effects which result in the main limitation of the method at present: the degradation of the sample by the electron probe. In the worst cases this degradation is so rapid as to preclude diffraction studies at all, and even in the more favourable cases there may remain doubt as to whether the structural information gained is truly representative of undamaged material.