Spatially Resolved EELS

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Above: Annular Dark Field (ADF) Imaging and Electron Energy Loss Spectroscopy (EELS) analytical techniques. In ADF imaging, electrons in the beam undergo large angle elastic scattering when they pass close to atoms within the specimen. These electrons are caught by an annulus detector, generating a signal used to form a scanned image -- displayed at the top in the right figure for a probe size of 2 Å in GeSi. Electrons which undergo only small angle deflection also lose some energy to the specimen. An Electron Spectrometer separates these electrons according to their energy, producing Electron Energy Loss Spectra. The spectra in the lower right summarize the silicon 2p core absorption edge at 99.86 eV for various locations in the image. The detailed shape of this edge can be interpreted in terms of the conduction bands in the Ge30Si70 specimen. [1] Since ADF imaging provides a very direct simple representation of the specimen structure, it can usually be compared with structural model calculations as indicated in the lower left image. (Model structure from Chelikowski. [2])

[1] P.E. Batson, Atomic Resolution Electronic Structure in Silicon-Germanium Alloys, J. Electron Microscopy 45, 51-58 (1996).

[2] P.E. Batson, Structural and Electronic Characterization of a Dissociated 60° Dislocation in GeSi, Phys. Rev. B 61, 16633-16641 (2000).