Z-contrast STEM using an annular detector can provide an intuitively interpretable, column-by-column, compositional map of crystals. Incoherent imaging reduces dynamical effects to second order so that the map directly reflects the positions of the atomic columns and their relative high-angle scattering power. This article outlines how these characteristics arise, presents some examples of the insights available from a direct image, and discusses recent developments of atomic-resolution microanalysis, direct structure retrieval by maximum entropy analysis, and Z-contrast imaging at 1.4 Å resolution using a 300-kV STEM.

Photoelectron imaging is a novel way of imaging the distribution of specific cell surface components. The basic principle is the photoelectric effect, in which electrons are ejected from the specimen by UV light. There are two primary forms of image contrast in photoelectron microscopy: material contrast and topographical contrast. Material contrast, provided by differences in photoelectron quantum yields, makes it possible to select labels that appear bright against the darker background of the cell surface. Topographical contrast ensures that label distribution can be interpreted in the context of cellular structures. By varying the wavelength of the exciting light, the contrast between label and cell surface can be controlled (tuned) to produce images ranging from a primarily topographical view of the surface to those showing only the label distribution. Being an emission-based technique, photoelectron imaging shares with fluorescence microscopy the ability to image label distributions at low magnification. However, unlike fluorescence microscopy the photoelectron image is formed by electrons, which generates a greater level of attainable resolution. Label contrast and wavelength-dependent tunability of contrast is illustrated with images of silver-enhanced immunogold-labeled cell surfaces, including selective labeling of cells in mixed-cell co-cultures, the cell surface CD44 adhesion protein on human glioma cells, fibronectin patterns on human fibroblasts, and the human transferrin receptor on MCF-7 human breast carcinoma cells.

A 1/2[0001](0001) stacking fault and a planar 60° rotational domain boundary on the (0001) plane in as-grown CVD α-Si3N4 crystals have been characterized by high-resolution electron microscopy and image simulation. As reported previously, two types of coherent boundaries have been observed in this material, namely, stacking faults and rotational domain boundaries. The former involves only a translational displacement, while the latter separates two grains by a 60° rotation in addition to a translation. Inasmuch as the difference resulting from the rotational component can hardly be detected by high-resolution electron microscopy, care must be taken to analyze them first by analytical electron microscopy. In this paper, these two types of boundaries are studied and structural models are constructed that give simulated images in satisfactory agreement with observed images.

Results concerning the calibration and use of a new ultrahigh vacuum (UHV) surface preparation and analysis system are reported. This Sample Preparation Evaluation Analysis and Reaction (SPEAR) side chamber system replaces an older surface side chamber that was attached to a Hitachi UHV H-9000 microscope. The system combines the ability to prepare clean surfaces using sample heating, cooling, ion milling, or thin film growth with surface analytical tools such as Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM), along with atomic surface structure information available from high-resolution transmission electron microscopy (HREM). The chemical sensitivity of the XPS and AES are demonstrated in preliminary studies of catalytic and semiconductor samples. In addition, the surface preparation capabilities are also demonstrated for the Si(100) and Ge(100) surfaces, including the ability to acquire secondary electron images during milling. During operation, the entire system is capable of maintaining the UHV conditions necessary for surface studies.