Morphological Symmetry Breaking During Epitaxial Growth at Grazing   Incidence
  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. 
Jianxin Zhong, Enge Wang, Qian Niu and Zhenyu Zhang