Published online by Cambridge University Press: 10 February 2011
Options are discussed which allow to distinguish equilibrium arrays of strained islands from kinetically-controlled arrays. Finite-temperature thermodynamic theory is developed for equilibrium arrays of two-dimensional monolayer-high islands in heteroepitaxial systems at submonolayer coverage. It is shown that the entropy contribution to the Helmholtz free energy of the system favors formation of small islands and results in the shrinkage of the islands with increasing temperature. The average size of islands decreases tremendously with respect to zero-temperature size at temperatures far below the characteristic energy of island formation. Such a temperature dependence can be the basis for decisive experiments aimed to distinguish between thermodynamic and kinetic effects on the formation of arrays of 2D islands. The theory is able to explain results of high-resolution electron microscopy of submonolayer arrays of InAs/GaAs(001) islands. Their formation is predominantly influenced by thermodynamics.
Permanent address: A.F. Ioffe Physical Technical Institute, St. Petersburg 194021, Russia.