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A radial heterojunction nanowire diode (RND) array consisting of a ZnO (shell)/Si (core) structure was fabricated using conformal coating of a n-type ZnO layer that surrounded a p-type Si nanowire. In both ultraviolet (UV) and visible ranges, the photoresponsivity of the RND was larger than that of a planar thin film diode (PD) owing to the efficient carrier collection with improved light absorption. Compared to a PD, in the forward bias, a 6 μm long RND resulted in a ∼2.7 times enhancement of the UV responsivity at λ=365 nm, which could be explained based on the oxygen-related hole-trap mechanism. Under a reverse bias, UV-blind visible detection was observed while the UV response was suppressed.

Vertically grown Si wire arrays were fabricated on a large scale by the Ni-catalyzed vapor-liquid-solid method. A single Si wire has a length of several tens of micrometers with a pure Si stem and a NiSi2 tip. The NiSi2 tip was spontaneously formed on a Si wire due to a slight lattice mismatch relative to Si. Further, this system provides a Schottky contact having a rectifying ratio of ∼102 with a low leakage current of about 2.88×10−10 A. The growth mechanism of vertical Si wires and the performance of a Schottky diode are discussed.