Size dependence in self-bending mechanism of Ge/Si bilayer nanofilms

The governing mechanism for a self-bending of Ge/Si bilayer epitaxial nanofilms that results in the formation of various nanostructures (nanotube, nanohelix, etc.) has been investigated using a molecular dynamics simulation. The effect of misfit stress between Ge and Si layers, surface stress due to the surface reconstruction and the anisotropy of elastic modulus on the bending behavior and the effect of film thickness on the relative strength of the individual factors are clarified. All experimentally and theoretically reported results that show sometimes a mutual disagreement could be reconciled, which enabled a more elaborate control of nanostructure formation.