Determination of the size, shape, and composition of indium-flushed self-assembled quantum dots by transmission electron microscopy

Single and multiple layers of self-assembled InAs quantum dots (QDs) produc ed by the indium-flush technique have been studied by transmission electron microscopy (TEM) in an effort to develop techniques to reproducibly grow Q Ds of uniform size and shape. To monitor the changes in QD dimensions, plan -view samples of capped single layers were studied as well as cross-section al samples of QDs in multiple layers and stacks. The changes in the observe d round- and square-shaped QD images under various plan-view TEM imaging co nditions, as well as the contrast reversal in the center of QD images viewe d in cross-section are modeled using the many-beam Bloch-wave approach, inc luding strain. The sizes and shapes of the QDs are determined through the i nterpretation of the observed (primarily strain) contrast in plan-view and the observed (primarily atomic number) contrast in cross-sectional TEM. (C) 2000 American Institute of Physics. [S0021-8979(00)03217-5].