The secondary electron generation process is studied in an ultra-high vacuum scanning transmission electron microscope using electron coincidence spectroscopy. Production pathways for secondary electrons are determined by analyzing coincidences between secondary electrons and individual excitation events. The ultimate spatial resolution available in scanning electron microscopy is limited by the delocalization of the secondary electron generation process. This delocalization is studied using momentum resolved coincidence electron spectroscopy. The fraction of secondary electrons resulting from localized excitations can explain the high spatial resolution observed in secondary electron microscopy images.

Structure changes of Si(111)-Pb surfaces due to deposition and heat treatment are studied by REM-RHEED. Surface structures observed are summarized as a phase diagram. Formation of an incommensurate layer(α) and a phase transition between incommensurate structures of α and α′ is described.

Reflected high energy electrons have been employed for studying surfaces of single crystal oxides in real and reciprocal space. The techniques used include reflection high energy electron diffraction (RHEED), reflection electron microscopy (REM), scanning reflection electron microscopy (SREM), and reflection electron energy loss spectroscopy (REELS). These methods have provided much information on surface morphology as well as the atomic and electronic structure of MgO, ∝-Al2O3, ∝ -Fe2O3, SiO2, TiO2 (rutile), and ZnO single crystals. Analyses for chemical composition and electronic states are possible using SREM and REELS. Surfaces terminating at different atomic layers of large-unit-cell materials have been determined in REM images and also in REELS data obtained under REM and SREM. Surface modification due to bombardment with the incident electron beam is pronounced on some oxide surfaces. These processes have been investigated with the REM imaging and REELS techniques.

Z-contrast imaging has been shown to be an effective method for obtaining a highresolution image from a scanning transmission electron microscope (STEM). The incoherent nature of the high-angle scattering makes image interpretation straightforward and intuitive with the resolution limited only by the 2.2 Å electron probe. The optimum experimental conditions for Z-contrast imaging also coincide with those used for analytical microscopy, enabling microanalysis to be performed with the same spatial resolution as the image. The detection limits afforded by a parallel detection system for electron energy loss spectroscopy (EELS) allows column-by-column core-loss spectroscopy to be performed using the Z-contrast image to position the electron probe. Preliminary results from the study of Yba2Cu3O7-δ illustrate the spatial resolution available with this technique and the potential applications for materials science.