The measurement of absolute crystal polarity is crucial to understanding the structural properties of many planar defects in compound semiconductors. Grain boundaries, including twin boundaries, in the sphalerite lattice are uniquely characterized by the crystallographic misorientation of individual grains and the direction of the crystal polarity in domains adjoining the grain boundary. To evaluate crystal polarity in gallium phosphide (GaP), asymmetrical interference contrast in convergent-beam electron-diffraction (CBED) patterns was used to ascertain the nature and direction of polar bonds. The direction of the asymmetry in the electron diffraction reflections was correlated with the crystal polarity of a sample with known polarity. The CBED technique was applied to determine the polar orientation of grains adjoining Σ = 3 coherent and lateral twin boundaries in polycrystalline GaP.

The accuracy of Na measurements in biological cryosections has been improved through replacement of the 8 μm Be window of the Si(Li) detector with a Super Atmospheric Thin Window (SuperATW) window mounted on a germanium electron microscope (GEM) detector. Greater accuracy of Ca measurements was also attained when a GEM detector instead of an Si(Li) detector was used for analysis of total Ca concentrations in cardiac muscle. Although the advantage of improved sensitivity for Na and Ca is lost in spot mode analysis because of the overriding contribution of biological variability, this advantage becomes important in X-ray mapping. We compared the two systems by analyzing cryosections of identical biological material under comparable conditions. We found that Si contamination in thin biological cryosections is unpredictable; it may be widespread and differ in degree in various cell compartments of the same cell. Hence, a correction for Si contamination should be included in the calculations of elemental concentrations. We suggest here a procedure for measuring and subtracting Si contamination from elemental spectra.

An in-lens Schottky field emission scanning electron microscope (SEM) combined with a transmission electron microscope (TEM)-type cold-stage and a chromium (Cr) sputter-coating system was developed to rapidly prepare and cryo-image biological specimens to attain accurate nanometer-level structural information. High-resolution topographic images at high primary magnification ([eg ]200,000 times) were digitally recorded with very short dwell times and without beam damage. Plunge freezing in ethane, followed by fracturing, Cr coating, and in-lens cryo-high-resolution scanning electron microscope (HRSEM) imaging directly revealed macromolecular features of yeast cells, platelets, and cell-free elastin analogues. The 'vitreous' nature of bulk water in its solid state appeared featureless in cryo-HRSEM images, suggesting that if ice crystals were present they would be [el ]2–3 nm (the approximate instrument resolution on cryo-specimens). Compared to technically difficult and indirect freeze-fracture TEM replicas, cryo-HRSEM samples are fully hydrated, unfixed, noncryoprotected specimens immersed in featureless ice. The time necessary to cryo-immobilize the specimen and record the image is <3 hr. The hexagonal arrays of intramembrane particles on the protoplasmic face of yeast cells and differences in surface morphology between thrombin-stimulated and quiescent platelets were assessed. A clear interface line between collapsed elastin fibril lacework and vitreous lakes was commonly observed. These experiments demonstrate the feasibility of this technique to rapidly evaluate macromolecular features in cryofixed cells and cell-free systems.

With the ultrahigh vacuum variable-temperature scanning tunneling microscope (UHV-VT-STM), atomic-level observation has been achieved. An ultrahigh vacuum atomic force microscope (UHV-AFM) has also been developed, with success in obtaining atom images where observation in noncontact (NC) mode with a frequency modulation (FM) detection method was attempted. Using the FM detection method in the constant oscillation amplitude of the cantilever excitation mode, we have obtained atomic-resolution images of Si(111) 7 × 7 structures and Si(100) 2 × 1 structures and other structures together with STM images in an ultrahigh vacuum environment. Also shown here are contact potential difference (CPD) images using the NC-AFM method.