Interfacial Atomic Number Contrast in Thick TEM samples (original) (raw)
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Scanning transmission electron microscopy (STEM) has been widely used for characterization of materials; to identify microand nano-structures within a sample and to analyze crystal and defect structures. High-angle annular dark field (HAADF) STEM imaging using atomic number (Z) contrast has proven capable of resolving atomic structures with better than 2 Å lateral resolution. In this work, the HAADF STEM imaging mode is used in combination with multislice simulations. This combination is applied to the investigation of the temperature dependence of the intensity collected by the HAADF detector in silicon, and to convergent beam electron diffraction (CBED) to measure the degree of chemical order in intermetallic nanoparticles. The experimental and simulation results on the high–angle scattering of 300 keV electrons in crystalline silicon provide a new contribution to the understanding of the temperature dependence of the HAADF intensity. In the case of 300 keV, the average high-angle...
Surface Science, 1990
A new theory of Low Energy Electron Diffraction (LEED) is presented in which the relevant multiple scattering equations are solved in the angular momentum representation within the framework of real-space multiple scattering theory (RS-MST). This approach avoids the plane wave basis used in many conventional LEED techniques and its associated limitations when applied to the calculation of LEED intensities from open surfaces containing small bulk interplanar spacings. In particular, high Miller index, stepped surfaces which lie beyond the present capabilities of conventional LEED, can now be treated in a relatively efficient and convergent manner. The new theory is tested by evaluating I-V spectra from the (100), (311), (331) surfaces of Cu which are compared with the results of a layer doubling (LD) LEED calculation. Excellent agreement is obtained in the (100) and (311) cases, for which the LD approach is expected to be applicable. The (311) surface is about the highest index fcc surface which can reasonably be attempted with the existing approaches. The results obtained for the case of the (331) surface using the LD and the RS-MST approaches agree up to about E = 100eV, beyond which the LD process fails to converge. We discuss and contrast the convergence properties of both methods.