Thermodynamic theory of two-dimensional to three-dimensional growth transition in quantum dots self-assembly

Abstract

A thermodynamic model has been proposed to address the transition from the two-dimensional to three-dimensional growth modes in the quantum dots self-assembly. It was found that the surface energy density of substrates and the mismatch between quantum dots and substrates play key roles in the transition of the growth modes. The high (low) surface energy density of substrate and the low (high) mismatch between quantum dots and substrate result in the large (small) critical thickness of the wetting layer, which further determines the growth mode of quantum dots. These findings suggested that we could control the transition of the quantum dots growth mode by substrate manipulation. The theoretical results were consistent with experimental observations, which implied that the established thermodynamic theory could be expected to be a general approach for pursuing the evolution of the growth mode in the quantum dots self-assembly.

Hybrid Analytical–Monte Carlo Model of In/GaAs(001) Droplet Epitaxy: Theory and Experiment

“…The energy stored in the strained layer causes the formation of quantum dots to ensure the relaxation of the system. The thickness of the wetting layer and its value critical for the quantum dot formation are known to decrease with either increasing temperature or the degree of lattice mismatch corresponding to the energy in the layer . There are no stresses in the case of DE since the supersaturated vapor transforms into the liquid phase on the substrate at temperatures typical of such type of epitaxy.…”

“…There is still no shared opinion on how the islands are emerging and growing and how the ensembles of droplets are being formed. The Volmer–Weber growth mode implies that the interactions between adatoms are stronger than between those and the surface, whereas islands growing in the Stranski–Krastanov mode are formed after the strained wetting layer has reached its critical thickness . Since both liquid three‐dimensional islands and the wetting layer can be observed during the process of the In/GaAs(001) DE, the type of growth mode realized in this system remains unclear.…”

“…The Volmer-Weber growth mode implies that the interactions between adatoms are stronger than between those and the surface, [15] whereas islands growing in the Stranski-Krastanov mode are formed after the strained wetting layer has reached its critical thickness. [1,16] Since both liquid three-dimensional islands and the wetting layer can be observed during the process of the In/ GaAs(001) DE, the type of growth mode realized in this system remains unclear. The evolution of the island shape and its critical size under certain growth conditions does not seem to be straightforward enough either.…”

Self‐Assembled InAs/GaAs Coupled Quantum Dots for Photonic Quantum Technologies

“…While the original work discusses a change in growth mode from 2D to 3D, so‐called layer plus island growth, modern epitaxial techniques have related this transition to strain and relaxation in the crystal lattice. This S–K growth mode is shown schematically in Figure . Here, the energy of restructuring the surface of a growing 2D film is considered as part of the total of the strain and surface energies of the growth.…”

“…Schematic of the Stranski–Krastanov growth mode. Reproduced with permission . Copyright 2010, Royal Society of Chemistry.…”