Heteroepitaxy of semiconductors on two-dimensional (2-d) atomic layered materials enables the use of flexible and transferable inorganic electronic and optoelectronic devices in various applications. Herein, we report the shape-and morphology-controlled van der Waals (vdW) epitaxy of ZnO nanostructures on hexagonal boron nitride (hBN) insulating layers for an architectured semiconductor integration on the 2-d layered materials. The vdW surface feature of the 2-d nanomaterials, because of the surface free of dangling bonds, typically results in low-density random nucleation-growth in the vdW epitaxy. The difficulty in controlling the nucleation sites was resolved by artificially formed atomic ledges prepared on hBN substrates, which promoted the preferential vdW nucleation-growth of ZnO specifically along the designed ledges. Electron microscopy revealed crystallographically domain-aligned incommensurate vdW heteroepitaxial relationships, even though ZnO/hBN is highly latticemismatched. First-principles theoretical calculations confirmed the weakly bound, noncovalent binding feature of the ZnO/hBN heterostructure. Electrical characterizations of the ZnO nanowall networks grown on hBN revealed the excellent electrical insulation properties of hBN substrates. An ultraviolet photoconductor device using the vdW epitaxial ZnO nanowall networks/ hBN heterostructure was further demonstrated as an example of hBN substrate-based device applications. The architectured heteroepitaxy of semiconductors on hBN is thus expected to create many other device arrays that can be integrated on a piece of substrate with good electrical insulation for use in individual device operation.

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A new memristors-based resistive logic computation unit is introduced. By controlling the memristors' conditional set operation adaptively to one of the input polarities, bipolar signal multiplication of an input and a stored reference bit is performed by unipolar memristor devices and control switches. The multiplication result is registered in an output nonvolatile memristor so that the computed output can be accessed anytime later on by reading the output memristor's status.Introduction: Voltage-actuated bipolar memristive devices enable resistive nanocomputing where memristive devices uniquely offer a variety of new computing functionalities such as the recently reported stateful Boolean logic gates [1,2]. This Letter introduces a resistive multiplier that can be embedded in hybrid integrated circuits consisting of bistable memristive devices and CMOS switches. With memristors' nonvolatile memory function and their conditional set/reset, this resistive multiplier can execute, even with passive unipolar resistances, exclusive OR (XOR) equivalent bipolar multiplications, in two phases. The function of the proposed resistive multiplier is demonstrated for XOR operation with inherent register capability.

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