We have demonstrated a NH 3 , NO 2 and water vapour sensor based on poly(m-aminobenzene sulfonic acid) functionalized single-walled carbon nanotube (SWNT-PABS) networks. The SWNT-PABS based sensors were fabricated by simple dispersion of SWNT-PABS on top of prefabricated gold electrodes. SWNT-PABS sensors showed excellent sensitivity with ppb v level detection limits (i.e., 100 ppb v for NH 3 and 20 ppb v for NO 2) at room temperature. The response time was short and the response was totally reversible. The sensitivity could be tuned by adjusting the sensor initial resistance. The sensors were also suitable for monitoring relative humidity in air.

Point contact reactions between a Si nanowire and a Ni nanowire are reported in which the Si nanowire is transformed into a single crystal NiSi with an epitaxial interface which has no misfit dislocation. The reactions were carried out in situ in an ultrahigh vacuum transmission electron microscope. The growth of the NiSi occurs by the dissolution of Ni into the Si nanowire and by interstitial diffusion from the point of contact to the epitaxial interface. The point contact reactions have enabled the authors to fabricate single crystal NiSi∕Si∕NiSi heterostructures of atomically sharp interfaces for nanoscale devices.

CdTe nanowires with controlled composition were cathodically electrodeposited using track-etched polycarbonate membrane as scaffolds and their material and electrical properties were systematically investigated. As-deposited CdTe nanowires show nanocrystalline cubic phase structures with grain sizes of up to 60 nm. The dark-field images of nanowires reveal that the crystallinity of nanowires was greatly improved from nanocrystalline to a few single crystals within nanowires upon annealing at 200 °C for 6 h in a reducing environment (5% H(2)+95% N(2)). For electrical characterization, a single CdTe nanowire was assembled across microfabricated gold electrodes using the drop-casting method. In addition to an increase in grain size, the electrical resistivity of an annealed single nanowire (a few 10(5) Ω cm) was one order of magnitude greater than in an as-deposited nanowire, indicating that crystallinity of nanowires improved and defects within nanowires were reduced during annealing. By controlling the dopants levels (e.g. Te content of nanowires), the resistivity of nanowires was varied from 10(4) to 10(0) Ω cm. Current-voltage (I-V) characteristics of nanowires indicated the presence of Schottky barriers at both ends of the Au/CdTe interface. Temperature-dependent I-V measurements show that the electron transport mode was determined by a thermally activated component at T>-50 °C and a temperature-independent component below -50 °C. Under optical illumination, the single CdTe nanowire exhibited enhanced conductance.

No abstract

No abstract