TEM image contrast from antiphase domains in GaAs: Ge(001) grown by MBE

Antiphase domains occur in thin GaAs epitaxial films grown on Ge(001) by molecular beam epitaxy. The domains have been imaged by transmission electron microscopy using 200-type reflections in dark field. The carefully chosen imaging conditions with convergent illumination ensure that doubly diffracted beams from a pair of first order Laue zone discs contribute to the singly diffracted 200-type beams. The three Bragg reflections may add in or out of phase to give domains in either light or dark contrast depending on their polarity.