Kinetic Monte Carlo Simulation of Heteroepitaxial Growth: Wetting Layers, Quantum Dots, Capping, and NanoRings

A new kinetic Monte Carlo algorithm that efficiently accounts for elastic strain is presented and applied to study various phenomena that take place during heteroepitaxial growth. For example, it is demonstrated that faceted quantum dots occur via the layer-by-layer nucleation of pre-pyramids on top of a critical layer with faceting occurring by anisotropic surface diffusion. It is also shown that the dot growth is enhanced by the depletion of the critical layer which leaves behind a wetting layer. Capping simulations provide insight into the mechanisms behind dot erosion and ring formation. The algorithm used for the simulations presented here is based on the observation that adatom and dimer motion is essentially decoupled from the elastic field. This is exploited by decomposing the film into two parts: the weakly bonded portion and the strongly bonded portion. The weakly bonded portion is taken to evolve independent of the elastic field. In this way the elastic field need only be updated infrequently. Extensive validation reveals that there is little loss of fidelity but the algorithm is fifteen to twenty times faster.