The effect of strains on the local crystallographic symmetry and structure of a Si/GexSi1minus;xmodel heterostructure grown on a (100) silicon substate was studied using convergent beam electron diffraction techniques and a crosshyphen;sectional specimen geometry. The alloy layers are seen to distort into relaxed tetragonal and monoclinic structures which are dependent on position and/or alloy composition. These observations can be explained in terms of strain relaxation in a thinhyphen;film specimen and deviations of the substrate from a perfect (100) orientation. The results have implications not only for the use of crosshyphen;sectioned specimens in the characterization of strainedhyphen;layer heterostructures, but also for the band engineering of Si/GexSi1minus;xstrainedhyphen;layer superlattices and other materials which are grown on vicinal (100) and other lowhyphen;symmetry substrate orientations. In particular relaxed tetragonal and monoclinic structures may be quite relevant to the emerging science of strainhyphen;induced lateral confinement of carriers in quantum well semiconductors.
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