Size selection of the cooperative ridge-trench formation in heteroepitaxial systems

The cooperative ridge-trench (CRT) formation on heteroepitaxial systems, the process controlling the self-assembly of quantum dot molecules, is investigated by simulating the process and by analyzing the corresponding energy change. The results suggest that the CRT formation is the competition of two exclusive pathways: namely, the growth of the outermost structure and the gradual formation of a new facet structure adjacent to the existing one. The first pathway dictates the process initially, while the second one is more energetically favorable once the size of the outermost structure reaches a critical value. The competition repeats, resulting in the CRT formation.