Abstract
We propose a nano-scale current-direction-switching device(CDSD) that operates based on the novel phenomenon of geometrical asymmetry between two hot-electron generating plasmonic nanostructures. The proposed device is easy to fabricate and economical to develop compared to most other existing designs. It also has the ability to function without external wiring in nano or molecular circuitry since it is powered and controlled optically. We consider a such CDSD made of two dissimilar nanorods separated by a thin but finite potential barrier and theoretically derive the frequency-dependent electron/current flow rate. Our analysis takes in to account the quantum dynamics of electrons inside the nanorods under a periodic optical perturbation that are confined by nanorod boundaries, modelled as finite cylindrical potential wells. The influence of design parameters, such as geometric difference between the two nanorods, their volumes and the barrier width on quality parameters such as frequency-sensitivity of the current flow direction, magnitude of the current flow, positive to negative current ratio, and the energy conversion efficiency is discussed by considering a device made of Ag/TiO2/Ag. Theoretical insight and design guidelines presented here are useful for customizing our proposed CDSD for applications such as self-powered logic gates, power supplies, and sensors.
Highlights
Such a devices as the current-direction-switching-device (CDSD) in this paper
The use of metallic nano-particles as a light-harvesting medium is more desirable compared to bulk-metals, semiconductors or molecules, since plasmon-enhanced electric fields in metallic nano-particles can generate hot electrons more efficiently than the direct electron excitation mechanism used in other media
We have derived the rate of electron flow in such a structure, made of two nanorods, by using the single-electron wave function and the corresponding eigen energy states of an electron inside each nanorod under a periodic perturbation
Summary
Such a devices as the current-direction-switching-device (CDSD) in this paper. Such nanoscale, optically controlled, power supply devices will allow designing self-powered logic-gates for energy/information processing, bio-sensors, optical sensors and power supply units, leading to nano and molecular circuits that can function without external wiring. The possibility of switching a plasmon-induced photo-current direction based on the geometrical asymmetry of nano-particles has not been discussed so far in the published literature Such systems can offer higher mechanical and chemical stability than the existing fluid-based molecular systems. The use of metallic nano-particles as a light-harvesting medium is more desirable compared to bulk-metals, semiconductors or molecules, since plasmon-enhanced electric fields in metallic nano-particles can generate hot electrons more efficiently than the direct electron excitation mechanism used in other media. A hybrid approach involving a combination of molecular components with nano-scale power supply may be better suited in practice for developing electronic circuits It has been shown experimentally in the context of light-harvesting applications that a sustainable electron flow in a circuit based entirely on optically excited electrons generated from a metallic nano-structure is possible[3,4,21]. On the other hand, such fast relaxation allows the hot-electron-based devices to have switching speeds approaching terahertz frequencies[26]
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