Electrical properties of a chemical sensor constructed from mats of GaN nanowires decorated with gold nanoparticles as a function of exposure to Ar, N2, and methane are presented. The Au nanoparticle decorated nanowires exhibited chemically selective electrical responses. The sensor exhibits a nominal response to Ar and slightly greater response for N2. Upon exposure to methane the conductivity is suppressed by 50% relative to vacuum. The effect is fully reversible and is independent of exposure history. We offer a model by which the change in the current is caused by a change in the depletion depth of the nanowires, the change in the depletion depth being due to an adsorbate induced change in the potential on the gold nanoparticles on the surface of the nanowires.
Gold nanoparticles assembled on a biopolymer template (see Figure) between metal electrodes on an insulating substrate are shown to exhibit unambiguous single electron charging effects that are found to depend on the nanoparticle properties and the geometrical contraints imposed by the biopolymer. The results support the idea of using nanoparticles in conjuction with biomolecular organization to produce nanoscale systems with defect‐tolerant current–voltage behavior.
We discuss far-from-equilibrium electron transport in quantum waveguide structures at low temperatures.On slowly cooling the devices in the dark, the current-voltage characteristics are found to be similar to those of a quantum point contact. Exposure to light at low temperature alters the characteristics dramatically, with one or more regions of current-controlled negative differential conductance occurring. The characteristics can be returned to their prelight condition by annealing the samples above 120 K, which indicates that the effect is associated with the occupancy of DX centers in the Al Gai As. We argue that the negative differential conductance arises &om hotelectron bistabilities due to puddles of charge trapped in the waveguide by potential inhomogeneities associated with ionized DX centers.
The room temperature electrical characteristics of biopolymer-gold nanoparticle complexes show threshold behavior, periodic conductance features, and current-voltage scaling that together indicate the nonlinear transport is associated with single electron charging. Repeated measurements over a period of up to 80 h showed the characteristics change with time. The current-voltage scaling behavior is found to be time independent, while the position of the conductance features shifted randomly over periods of many hours. We show that the time dependence is consistent with a fluctuating background charge distribution and can be understood within the framework of the orthodox model of single electron transport that is modified to account for the relatively large self-capacitance of the nanoparticles.
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