Computer-aided analysis of TEM images of CdSe/ZnSe quantum dots

Self-organized CdSe/ZnSe quantum dots (QDs) were investigated by means of transmission electron microscopy (TEM). Plan-view diffraction contrast images each obtained under individual diffraction conditions showed different contrast behaviour. Bright-field imaging of single dots revealed circle-like contrast features. In the 04̄0 dark-field image a 2-fold symmetry and in the 2̄2̄0 dark-field image a nearly 4-fold symmetry of the contrast features were observed. Supplementary strain-field calculations using a finite-element method were compared with the experimental contrast features. The distributions of the several strain components chosen according to the certain diffraction conditions show the same symmetry and orientation as the experimental features.