Papers by Keyword: Metal Nanowires

Abstract: Metal atoms confined in finite cylindrical nanopores exhibit helical morphologies because of the high rotational symmetry of confined surfaces and energy minimum of (111) facets. Herein, we present adirect nanoconfinement induced helical symmetry breaking phenomenon resulting from asymmetric atomic arrangements around the surfaces of nanoconfinements. In cylindrical nanopores, the critical value transforming from helical nanowires to crystalline ones is larger than corresponding free-standing nanowires, indicating nanopores with high rotational symmetry are propitious to form (111)facets wrapped outside of nanowires

Abstract: The formation process of oxide nanotube via metal oxidation reaction was studied by transmission electron microscopy for Cu, Fe, and Ni nanowires. Cu2O and Fe3O4 nanotubes were formed after the oxidation of Cu and Fe nanowires with a diameter of 55 nm in air at 423 and 573 K for 3.6 ks, respectively. Both Cu2O and Fe3O4 nanotubes had a cylindrical interior pore with uniform diameter. On the other hand, Ni nanowires became bamboo-like structures of NiO with separate interior pores after oxidation at 673 K for 7.2 ks. The formation of the interior pores in Cu2O and Fe3O4 nanotubes and NiO bamboo-like structures can be explained by the rapid outward diffusion of metal ions through the oxide layers and the clustering of excess vacancies.

Abstract: Suspended gold nanowires can be made atomically thin with as many as five atoms, showing extremely large Au-Au bond distances. Using tools derived from Density Functional Theory (DFT) we study many questions posed by the experiments. First we use realistic molecular dynamics simulation to study the mechanisms of formation, evolution and breaking of these atomically thin Au nanowires under stress. We show how defects induce the formation one-atom chains that can grow as long as five-atoms before breaking. Results are in excellent agreement with experiments, except for the resulting shorter bond distances. In order to address this question, we use ab initio electronic structure calculations to show that the exceedingly large Au-Au interatomic distances experimentally obtained could be the effect of impurities. We studied the effect of single impurities H, B, C, N, O, S and small molecules as H2 on the nanowire's electronic and structural properties, in particular how they affect the maximum Au-Au bond length.