Method for evaluation of the Ehrlich-Schwoebel barrier to interlayer transport in metal homoepitaxy.

Abstract

A method of evaluating the step-edge barrier which determines the rate of interlayer diffusion during homoepitaxial growth is developed on the basis of a full and general consideration of the problem of the critical island size for second layer nucleation. Data about saturation island density, critical surface coverage for second layer nucleation, the surface diffusion coefficient, and binding energies of the nuclei of the second layer are required to evaluate the barrier. The procedure includes evaluation of the size of the critical nuclei formed on top of the growing two-dimensional (2D) islands and the temperature interval in which the nucleus size does not change. The values 0.31 eV and 0.44 eV estimated for the step-edge barriers on Pt(111) at 425 and 628 K are attributed to (100) and (111) faceted steps, respectively. Assuming a change of the mechanism of descent from (111) faceted steps to a low-barrier one at about 450 K, we argue that the above values are in agreement with the experimentally observed inversion of shape of the 2D islands with the temperature [Michely et al., Phys. Rev. Lett. 70, 3943 (1993)].