  It is shown that, in submonolayer growth at off-normal incidence, even much
less than one percent of transfer from the condensation energy of the deposited
atoms into adatom motion is sufficient to induce a net adatom current from the
illuminated edge of a two-dimensional island to the other edges, thereby
breaking the island symmetry. Such a symmetry breaking phenomenon is most
pronounced for deposition at grazing incidence. Comparison between our
theoretical predictions and existing experimental results confirms the general
validity of the model.
