Ridge National Laboratory, Oak Ridge, Tennessee 37831 § These authors contribute equally. AbstractSemiconductor heterostructures provide a powerful platform to engineer the dynamics of excitons for fundamental and applied interests. However, the functionality of conventional semiconductor heterostructures is often limited by inefficient charge transfer across interfaces due to the interfacial imperfection caused by lattice mismatch. Here we demonstrate that MoS 2 /WS 2 heterostructures consisting of monolayer MoS 2 and WS 2 stacked in the vertical direction can enable equally efficient interlayer exciton relaxation regardless the epitaxy and orientation of the stacking. This is manifested by a similar two orders of magnitude decrease of

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Using molecular dynamics (MD) simulation, we studied the structural transformation and breaking mechanism of a single crystalline copper nanowire under continuous strain. At a certain strain rate, an ensemble of relaxed initial states of the nanowire can preferentially go through one or more paths of deformation. In each deformation path, disordered atoms can be generated at the specific positions of the nanowire, where necking and breaking take place afterward. Such a breaking position is not predetermined; multiple initial states lead to a strain-rate-dependent, statistical distribution of breaking positions.

Size effects in the oriented-attachment (OA) growth process of Cu nanoseeds were found. Monodispersed Cu nanoseeds with average diameters of 2.2, 3.4, and 5.2 nm were controllably synthesized by the reduction of copper acetate in a boiling solvent and using dodecanethiol (DT) as a stabilizer and sulfur source of sulfide. These Cu nanoseeds were then treated under solvothermal conditions. When the diameters of Cu nanoseeds were smaller than 5 nm, Cu(2)S nanorods with lengths of approximately 30-100 nm and diameters of approximately 2-4 nm were obtained at lower temperatures, and Cu(2)S nanodisks with diameters of approximately 6-13 nm and thicknesses of approximately 2-4 nm were obtained at higher temperatures. Once the diameter of Cu nanoseeds was larger than 5 nm, only irregular particles were obtained, regardless of other conditions. The uniformity, which related to the density of DT on the surface of Cu nanoseeds, was the key for success of self-assembly of the final nanocrystals. High-resolution transmission electron microscopy images demonstrated that these nanorods, nanodisks, and particles were formed by an OA process of Cu nanoseeds into 1D, 2D, and 3D aggregates, which recrystallized into single crystals.