OBSERVATION OF PLANAR DEFECTS BY REFLECTION ELECTRON-MICROSCOPY

The intersections of planar defects with crystal surfaces are studied by reflection electron microscopy. Two types of contrast may be involv ed in imaging of the intersections of planar defects with crystal surf aces. The first type of contrast is diffraction contrast. It originate s from the difference of the diffraction conditions of the two parts o n either side of the fault, or from lattice distortions associated wit h the strain fields in the vicinity of planar defects, such as twin bo undaries. This type of contrast is observed and discussed for the 90 d egrees ferroelectric domain boundaries (twin boundaries in fact) in Ba TiO3 single crystals. The second type of contrast is the phase contras t produced by the surface steps associated with the defects such as st acking faults and slip faults. Examples of stacking faults on as-grown surfaces of Au spheres are discussed.