Quantum-dot nucleation in strained-layer epitaxy: Minimum-energy pathway in the stress-driven two-dimensional to three-dimensional transformation

José Emilio Prieto and Ivan Markov
Phys. Rev. B 72, 205412 – Published 9 November 2005

Abstract

The transformation of monolayer islands into bilayer islands as a first step of the overall two-dimensional to three-dimensional (2D-3D) transformation in the coherent Stranski-Krastanov mode of growth is studied for the cases of expanded and compressed overlayers. Compressed overlayers display a nucleation-like behavior: The energy accompanying the transformation process displays a maximum at some critical number of atoms, which is small for large enough values of the misfit, and then decreases gradually down to the completion of the transformation, nonmonotonically due to the atomistics of the process. On the contrary, the energy change in expanded overlayers increases up to close to the completion of the transformation and then abruptly collapses with the disappearance of the monoatomic steps to produce low-energy facets. This kind of transformation takes place only in materials with strong interatomic bonding. Softer materials under tensile stress are expected to grow predominantly with a planar morphology until misfit dislocations are introduced, or to transform into 3D islands by a different mechanism. It is concluded that the coherent Stranski-Krastanov growth in expanded overlayers is much less probable than in compressed ones for kinetic reasons.

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  • Received 12 August 2005

DOI:https://doi.org/10.1103/PhysRevB.72.205412

©2005 American Physical Society

Authors & Affiliations

José Emilio Prieto*

  • Centro de Microanálisis de Materiales and Instituto Universitario “Nicolás Cabrera,” Universidad Autónoma de Madrid, E-28049 Madrid, Spain

Ivan Markov

  • Institute of Physical Chemistry, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria

  • *Electronic address: joseemilio.prieto@uam.es
  • Electronic address: imarkov@ipchp.ipc.bas.bg

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Issue

Vol. 72, Iss. 20 — 15 November 2005

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