TEM HREM VISUALIZATION OF NM-SCALE COHERENT INAS ISLANDS (QUANTUM DOTS) IN A GAAS MATRIX/

The electron microscope determination (high resolution HREM and conven tional diffraction contrast TEM) of the structure (geometry, size, sha pe, etc.) of nm-scale objects is of great interest for the creation of novel semiconducting materials of reduced dimensions as, e.g., quantu m dots (QDs) and quantum wires. HREM contrast simulations based on mol ecular dynamics structure modelling are applied to check the visualiza tion of coherently strained nm-scale InAs islands embedded in a GaAs m atrix. Being of pyramidal shape, InAs islands always seem to be trunca ted owing to lower In content on top of the pyramid and to the high le vel of strains around the island. Optimum imaging conditions are analy sed to reveal shape and size of such objects.