Origins of size-dependent lattice dilatation in tetragonal Sn nanowires: Surface stress and growth stress

Through experiments and theoretical analyses, we demonstrate that Sn nanowires can shrink or expand when the radius decreases from 120 to 1.2 nm. Single crystalline nanowires manifest [100]-longitudinal lattice dilatations that originate from the strong anisotropy of the surface stress. Compressive growth stress, which is generated in the radial direction during the growth of nanowires within templates, leads to greater elongation due to the Poisson effect. The surface stress-induced lattice strains are intrinsic, whereas the growth stress-induced lattice strains can be released. For polycrystalline nanowires, lattice contractions occur because the anisotropy of surface stresses is effectively reduced. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3493179]