2010 Innovation Awards
collect the low-energy secondary electron signal and the annular dark-field (ADF) signal. Because of the optical design of the microscope (Hitachi HD2700C), the high efficiency of the detectors, the high electrical and mechanical stability, the high-brightness source and ultra-fine probe, and the high voltage used (80–200 kV), this system has achieved a spatial resolution below 0.1 nm in both the surface and bulk imaging modes. For the secondary electron (SE) imaging mode, this resolution is a four-fold improvement compared with existing scanning electron microscopes. Te soſtware, developed mainly at BNL, is used for
analyzing image intensity and for noise reduction in both SE surface-imaging mode and in scanning transmission electron microscopy (STEM) mode. One soſtware feature is the automatic searching for identical atoms in the scanned area. Trough quantitative analysis using ADF images as the reference, it is possible to determine whether an atom is on the top or bottom of a support and the number of atoms in the beam path. In previously accepted theory, SE generation was
attributed to collective electron excitations resulting from inelastic scattering of incident electrons, and atomic resolution SE imaging was not thought possible. However, direct imaging of surface atoms using SEs now has been demonstrated, which indicates that SE generation is associated with momentum transfer of single-electron excitation events.
2010 September •
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