[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).
ADF Imaging and EELS Scattering Geometry
Ge30Si70 Imaging and EELS Example
On the left:
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] )