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By using a nanoprobe electron beam 4 A in diameter, the [001] nanodiffraction patterns of AlGaAs‐GaAs multiple‐quantum‐well structures have been formed and the epitaxial relationship between AlGaAs and GaAs is confirmed. The intensities of the (200) diffraction disk, monitored by a spot detector, are displayed in two ways: (1) the (200) dark‐field scanning transmission electron microscopy (STEM), which shows the layers of AlGaAs and GaAs in contrast, and (2) the (200) line‐scan profile, which reveals the (200) intensity distribution of a specimen region of uniform thickness. The thickness and the absolute Al concentration of AlGaAs layers are, respectively, determined from the contrast of, and the (200) thickness contour position in, the (200) dark‐field STEM images. The microanalysis on the (200) line‐scan profile is used to find the local Al concentrations in AlGaAs layers and to study the interface boundary between the layers of AlGaAs and GaAs. Diffusion of the Al atoms from the AlGaAs layer into the ...

The thickness dependence of ferroelectric domains in thin free‐standing BaTiO3 crystalline films has been studied by transmission electron microscopy. It is found that the widths of ferroelectric domains decrease as the film thickness decreases. This phenomenon may indicate that the ferroelectric properties of thin films are weakened due to surface relaxation effects, including lattice relaxation and a change of spontaneous polarization and charge compensation. The weakening of ferroelectric domains is suggested as a transition state from ferroelectric to paraelectric phase of the BaTiO3 thin film. The thickness of the surface relaxation layer of totally nonferroelectric film is on the order of 10 nm.

The REMEDIE system for reflection electron microscopy and electron diffraction at intermediate energies (0.5–20 keV) has been rebuilt with an improved imaging resolution of better than 10 nm, a convenient and versatile system for observation diffraction patterns and provision for specimen preparation and treatment suitable for surface structural studies. The current capabilities of the instrument are illustrated by results obtained from cleaved and annealed silicon (111) surfaces with or without thin deposited silver and gold layers.

X‐ray diffraction methods have been used to measure long‐ and short‐range order parameters for single crystals of the alloy Cu3Au held at elevated temperatures. It is shown that short‐range order parameters may be obtained by a three‐dimensional Fourier analysis of the ``scattering power'' for the diffuse background scattering of x‐rays, expressed as a function of reciprocal lattice coordinates. Appropriate experimental and computational procedures are outlined. Intensity measurements have been made with a special arrangement of a bent‐crystal monochromator and a Geiger‐counter spectrometer. Short‐range parameters are given for the first ten shells of atoms surrounding a given atom for three temperatures above the critical temperature of Cu3Au. These results, and those for the long‐range order parameter agree well with theoretical predictions.

A novel method for determining the local concentration of Al in the AlxGa1−xAs layer of AlxGa1−xAs‐GaAs multiple quantum well structures is reported. By scanning a 10 A electron beam across the interface, the (200) dark‐field scanning transmission electron microscopy (STEM) image shows the contrast of the AlxGa1−xAs‐GaAs multilayer since the intensity of the (200) diffraction is sensitive to the Al concentration. The line scan intensity profile of the (200) diffraction, along a uniform specimen region of known thickness, shows the intensity variation of the (200) diffraction and reflects the local content of Al in each region. The simulation of the nanodiffraction patterns produces a chart of the (200) diffraction intensity versus the Al concentration for the determination of the local change of the Al concentration. A molecular beam epitaxy grown AlxGa1−xAs‐GaAs specimen (x=0.57 as determined from Raman spectroscopy) is tested and the dark‐field STEM studies show two thin layers of x=0.46 at the 1/3 and ...

The appearance of phase‐contrast, Fresnel fringes and various forms of diffraction contrast in images produced by transmission scanning electron microscopes can be understood simply by invoking the principle of reciprocity to equate the imaging conditions to those relevant to a conventional electron microscope.

A system employing medium energy electrons (1–15 keV) for scanning microscopy and diffraction intensity measurements has been constructed. The specimen is situated in an UHV environment and can be cleaned by argon ion sputtering and heated up to 1000 °C. The resolution is currently about 300 A for scanning images formed when secondary electrons are detected. The use of diffracted beams to form images is shown to provide new types of information regarding the structure and defects of crystal surfaces. Intensities and intensity profiles of diffracted beams can be measured for comparison with theoretical data and structure analysis.