  The purpose of this paper is to report some new experimental and theoretical
results about the analysis of in-plane lattice spacing oscillations during
two-dimensional (2D) homo and hetero epitaxial growth. The physical origin of
these oscillations comes from the finite size of the strained islands. The 2D
islands may thus relax by their edges, leading to in-plane lattice spacing
oscillations during the birth and spread of these islands. On the one hand, we
formulate the problem of elastic relaxation of a coherent 2D epitaxial deposits
by using the concept of point forces and demonstrate that the mean deformation
in the islands exhibits an oscillatory behaviour. On the other hand, we
calculate the intensity diffracted by such coherently deposited 2D islands by
using a mean model of a pile-up of weakly deformed layers. The amplitude of
in-plane lattice spacing oscillations is found to depend linearly on the misfit
and roughly linearly on the nucleation density. We show that the nucleation
density may be approximated from the full-width at half maximum of the
diffracted rods at half coverages. The predicted dependence of the in-plane
lattice spacing oscillations amplitude with the nucleation density is thus
experimentally verified on V/Fe(001), Mn/Fe(001), Ni/Fe(001), Co/Cu(001) and
V/V(001).
