Kinetic Monte Carlo simulation of heteroepitaxial growth: Wetting layers, quantum dots, capping, and nanorings

Abstract

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.

Submonolayer growth study using a solid-on-solid model for 2 × 1 reconstructed surfaces of diamond-like lattices

“…For such systems, the multicomponent nature will complicate the SOS model and there would be more interaction parameters. In the case of heteroepitaxial growth of Ge on Si(001), our calculations can be thought of as a step towards adding surface details to the existing methods [48,54], which involve an elastic energy contribution to the hopping barrier. Further, a height dependent interaction energy is used to account for wetting effects.…”

Understanding the early stages of growth of Ge on Si(001) from lattice based simulations

“…In these models, surface energy anisotropy is included either using suitably modified bond models [19] or using explicit facet stabilization [25]. Such models can be tailored to study the shapes and evolution of quantum dot formation in these systems.…”

“…Heteroepitaxial growth has been studies using lattice models with explicit elastic effects, either in the form of harmonic springs [13][14][15][16][17][18][19][20][21][22] or using continuum models [23,24]. In these models, surface energy anisotropy is included either using suitably modified bond models [19] or using explicit facet stabilization [25].…”

Size calibration of epitaxial islands via a two-step growth protocol: Kinetic Monte Carlo and effective-medium theory study

“…The Stranski-Krastanov growth, 57 however, takes place under conditions close to thermodynamic equilib-58 rium [3,7,8]. In this case many complex processes of atomic exchange 59 between the QDs, the substrate and the wetting layer are taking place 60 in the system, so sophisticated modeling is needed for their accurate de-61 scription [9,10]. Because currently such modeling is not yet sufficiently 62 predictive, the control of the thermodynamically limited QD growth is 63 not an easy task.…”