Recent results of studying amorphous Ge and Si by electron microscopy are summarized. The annealing of amorphous Ge has been investigated by differential thermal analysis, and the energy of the surfaces separating ordered domains was found to be 950 ergcm2. In addition, it is shown through the construction of a model that ordered domains can be connected by regions of random network that are free from dangling bonds.

Observations of the effect of thermal diffuse scattering, single electron excitations and plasmon excitation on the quality of electron microscope images of crystals are presented and discussed. Preservation of image contrast after thermal diffuse scattering seems to be poor in practice but only a small fraction of the electrons accepted by the aperture are affected in this way. To a first approximation, contrast appears to be preserved after single electron excitation or plasmon excitation especially at small scattering angles where no evidence of interband transitions of the fast electron has been found. At larger scattering angles some loss of contrast occurs so that the size of the aperture can be important. The significance of the results is discussed with reference to electron microscopy of thick crystals, direct resolution of atomic positions and out-of-focus images.

Analysis of electron micrographs of stacking faults in cadmium shows that the spacing of the layers at the faults has the same anomalous c/a ratio as in the perfect crystal.

Electron transmission microscopy and selected area diffraction have shown that the dislocation loops in aluminium bombarded with 38 Mev alpha-particles lie generally upon the {110} planes with a [110] Burgers vector normal to the loop. These loops are only seen where the alpha-particles come to rest. The theory of diffraction contrast at dislocations (Hirsch et al. 1960) has been used to determine the sense of the Burgers vectors and shows that the loops are formed from interstitial atoms as previously inferred from their annealing behaviour (Barnes and Mazey 1960).

From measurements of the radius of curvature of extended dislocation nodes observed by transmission electron microscopy, stacking-fault energies have been determined for a number of copper and silver base aluminium and zinc solid solution alloys and also for a number of nickel-cobalt alloys. Rough estimates of about 40, 25 and 150 erg cm−2 respectively can be made of the stacking-fault energies of copper, silver and nickel. The accuracy of the measurement and the possibility of segregation of solute atoms to stacking faults are discussed.