Formation of three-dimensional quantum-dot superlattices in amorphous systems: Experiments and Monte Carlo simulations

Quantum dots ordered in regular lattices, called quantum-dot superlattices, offer numerous possibilities for the creation of novel materials. The formation of such structures during multilayer deposition has been studied and explained satisfactorily only in crystalline materials. Here we are reporting the spontaneous formation of quantum-dot superlattices in amorphous systems. The observed superlattices comprise Ge quantum dots embedded in amorphous SiO2 matrix. The internal structure and shape of Ge quantum dots can be controlled by postdeposition thermal annealing. The superlattices show collective behavior properties that appear to be the consequence of a regular ordering of quantum dots. The observed self-organized growth is explained and successfully simulated by a theoretical model based on the interplay of diffusion-mediated nucleation and surface morphology effects. The presented results can be applied more generally and show the ability of formation of regularly ordered, densely packed, and uniformly sized quantum-dot arrays in amorphous matrices.