Resolution limitations in the Electron microscopy of surfaces

Abstract

Atoms on surfaces scatter high voltage electrons in much the same way as isolated atoms and, in principle, could be imaged with the same resolution. The practical limits on resolution of surface structure arise from the complications imposed by the presence of the bulk sample. In high resolution transmission imaging of crystals in principle orientations, the contrast of the atomic rows is highly non-linear with thickness so that the addition of atoms on surfaces or the subtraction of atoms at vacancies gives very little contrast. Surface structure and internal point defects are best seen when the resolution is degraded by an objective aperture which excludes the inner Bragg reflections from the bulk lattice. The profile imaging technique remains as the only method for applying the full resolution of transmission electron microscopes to the imaging of surface atoms.