InxGa1−xAs quantum dots
in GaP(100) crystals prepared by the OMVPE technique are observed along
the [011] direction with a newly developed 200-kV spherical
aberration(Cs)-corrected HRTEM, a 200-kV annular dark-field
(ADF)-STEM, and a 200-kV conventional HRTEM equipped with a thermal
field-emission gun. The dots are 6–10 nm in size and strongly
strained due to the misfit of about 9% with the GaP substrate and GaP
cap layer. All of the cross-sectional high-resolution electron
micrographs show dumbbell images of Ga and P atomic columns separated
by 0.136 nm in well-oriented and perfect GaP areas, but the
interpretable images are limited to those taken with the
Cs-corrected HRTEM and ADF-STEM with Fourier filtering of
the images. The Cs-corrected HRTEM and ADF-STEM are
comparable from the viewpoint of interpretable resolution. A detailed
comparison between the Cs-corrected HRTEM images and the
simulated ones with electron incidence tilted by 1° to 5° from
the [011] zone axis gives information on local lattice
bending in the dots from the images around 0.1 nm resolution. This
becomes one of the useful techniques newly available from electron
microscopy with sub-Ångstrom resolution.