High-speed metal-semiconductor-metal ͑MSM͒ photodetectors based on Schottky-contacted core/ shell GaAs/AlGaAs and bare GaAs nanowires were fabricated and characterized. The measured core/shell temporal response has a ϳ10 ps full-width at half-maximum and an estimated corrected value less than 5 ps. The bare GaAs devices exhibit a slower response ͑ϳ35 ps͒ along with a slow decaying persistent photocurrent ͑ϳ80 s͒. The core/shell devices exhibit significantly improved dc and high-speed performance over bare nanowires and comparable performance to planar MSM photodetectors. The picosecond temporal response, coupled with picoampere dark current, demonstrate the potential for core/shell nanowires in high-speed imaging arrays and on-chip optical interconnects.

A vapor transport method is employed to synthesize single crystalline tellurium nanowires with tailorable size using tellurium powder in an inert atmosphere. The average nanowire diameter is tunable between 50 and 3000 nm with an associated length of 1 to 22 μm. Growth temperature and time are used to specifically control the behavior of supersaturation, leading to nucleation and morphological control in this vapor–solid growth regime. Analysis of the resulting nanowire product provides insight into the dominant reaction kinetics involved in these growths and suggests routes by which to control growth product. This methodology provides a practical approach to synthesizing high-quality tellurium nanowires of various sizes and their incorporation into two-dimensional mesh-like structures through controlled nucleation and growth dynamics.

We report on the spatial and temporal evolution of photoinduced charge generation and carrier separation in heteroepitaxial BiFeO(3) thin films deposited on Nb:SrTiO(3) as measured in ambient at room temperature with Kelvin probe and piezoresponse force microscopy. Contributions from the self-poled and ferroelectric polarization charge are identified from the time evolution of the correlated surface potential and ferroelectric polarization in films as grown and following poling, and at different stages and intensities of optical illumination. Variations in the surface potential with bias voltage, switching history, and illumination intensity indicate how both bulk ferroelectric photovoltaic and the domain wall offset potential mechanisms contribute to the photogenerated charge.

The electronic transport and gating characteristics in GaAs and Ge nanowires (NWs) are altered significantly following either indirect or direct exposure to a focused Ga+ ion beam (FIB), such as that used to produce Pt electrical contacts to NWs. While these results challenge the assumptions made in some previously reported work relating to the electronic properties of semiconductor NWs using FIB-assisted production of contacts and/or their leads, local electron beam induced deposition is shown to be a reliable and facile route for producing robust electrical contacts to individual vapor phase-grown NWs in a manner that enables study of their actual carrier transport properties.

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