Dark field transmission electron microscope images of III-V quantum dot structures

While 002 images can be used to determine the size and shape of dots, a density per unit area cannot be calculated in the cross section geometry without either measuring-or assuming-the specimen thickness. In multilayer structures, plan-view TEM images show the layers as overlapping, losing the information from individual layers. By tilting a cross-section specimen to allow imaging with the dark field 113 diffraction condition, the density in individual layers can be measured. Additional information, such as wetting layer thickness variations and alignment of dots due to surface roughness or substrate offcut, can also be obtained.