Near-atomic-resolution EELS in silicon-germanium alloys

Recent advances in instrumental capabilities now allow us to combine spatially resolved EELS with annular darkfield (ADF) imaging to relate the electronic or bonding behaviour of a small region to its atomic structure. Although still limited to projections of structures at the 0.2 nm level, the ADF imaging gives excellent information about the structure and composition of crystalline interfaces and defects. Spatially resolved EELS can then obtain the local bonding and electronic structure, with a similar spatial resolution, Using the silicon 2p core excitation as a probe of the conduction band density of states, it is possible to follow changes of these bands as a function of composition and defect structure in the Ge-Si alloy system. Effects due to local strain are also observable.