There has been significant emphasis recently on the synthesis of fivefold-twinned Ag and Cu nanowires, which are considered to be excellent candidates for transparent conductors in flexible and stretchable electronic devices.  A fundamental understanding of nanowire growth is important in achieving optimal syntheses.  We consider two types of nanowires:  Cu nanowires, whose growth is facilitated by Cl and adsorbed alkylamines, and Ag nanowires protected by PVP.  In the case of Cu, we use DFT calculations to show that disruption of alkylamine monolayers by chloride ions causes facet-selective Cu deposition, in agreement with electrochemical measurements.  This leads to selective growth of {100} facets and long nanowires.  In the case of Ag nanowires, we performed a detailed analysis of the seed structure and find this is akin to a Marks decahedron, with {111} “notches” at twin boundaries between {100} facets. We find that the density of islands on the {111} facets of growing wires is lower than that on {100} facets and that large islands nucleate on {111} facets.  Our climbing-image nudged-elastic band calculations of diffusion barriers based on embedded-atom method potentials indicate that diffusion in the {111} notches is significantly faster than diffusion on {100} facets.  Thus, the notches become “superhighways” that channel atom diffusion to the wire ends to increase wire aspect ratios.  Islands facilitate trapping of atoms on {111} facets.  We use finite Markov chains to model nanowire growth and to predict net atom fluxes from nanowire sides to the ends.  These simulations predict anisotropic nanowires similar to those seen experimentally.<br/>

Growth of fivefold-twinned Cu and Ag nanowires

2019 Spring National Meeting

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