Lattice-mismatch is an important factor for the heteroepitaxial growth of core-shell nanostructures. A large lattice-mismatch usually leads to a non-coherent interface or a polycrystalline shell layer. In this study, a conformal Ag layer is coated on Cu nanowires with dense nanoscale twin boundaries through a galvanic replacement reaction. Despite a large lattice mismatch between Ag and Cu (∼12.6%), the Ag shell replicates the twinning structure in Cu nanowires and grows epitaxially on the nanotwinned Cu nanowire. A twin-mediated growth mechanism is proposed to explain the epitaxy of high lattice-mismatch bimetallic systems in which the misfit dislocations are accommodated by coherent twin boundaries.

Superior photolysis stability of cuprous oxide grown on twinned Cu nanowires.

The glucose level is an important biological indicator for diabetes diagnosis. In contrast with costly and unstable enzymatic glucose sensing, oxide-based glucose sensors own the advantages of low fabrication cost, outstanding catalytic ability, and high chemical stability. Here, we fabricate a self-supporting spiky Cu x O/Cu nanowire array structure by electrochemical cycling treatment. The spiky Cu x O/Cu nanowire is identified to be a Cu core passivated by a conformal Cu 2 O layer with extruded CuO petals, which provides abundant active sites for electrocatalytic reaction in glucose detection. An interruptive potential sweeping experiment is presented to elucidate the growth mechanism of the spiky Cu x O/Cu nanostructure during the potential cycling treatment. The spiky Cu x O/Cu nanowire array electrode exhibits a sensitivity of 1210 ± 124 μA·mM –1 ·cm –2 , a wide linear detection range of 0.01–7 mM, and a short response time (<1 s) for amperometric glucose sensing. The study demonstrates a route to modulate oxide phase, crystal morphology, and electrocatalytic properties of metal/oxide core–shell nanostructures.

Surface diffusion is intimately correlated with crystal orientation and surface structure. Fast surface diffusion accelerates phase transformation and structural evolution of materials. Here, through in situ transmission electron microscopy observation, we show that a copper nanowire with dense nanoscale coherent twin-boundary (CTB) defects evolves into a zigzag configuration under electric-current driven surface diffusion. The hindrance at the CTB-intercepted concave triple junctions decreases the effective surface diffusivity by almost 1 order of magnitude. The energy barriers for atomic migration at the concave junctions and different faceted surfaces are computed using density functional theory. We proposed that such a stable zigzag surface is shaped not only by the high-diffusivity facets but also by the stalled atomic diffusion at the concave junctions. This finding provides a defect-engineering route to develop robust interconnect materials against electromigration-induced failures for nanoelectronic devices.

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