Plasmonic Multi-Tip Nano-Rectenna Cell for Broadband Infrared Conversion
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Solution Overview
Problem
Existing rectennas face challenges in efficiently converting infrared and visible light frequencies into DC electricity due to limitations in diode frequency response, particularly parasitic capacitance in planar Metal-Insulator-Metal (MIM) diodes, which restrict operation to lower frequencies.
Innovation Solution
The use of tapered, conical tips with a plasmonic coating as both antennas and diodes, integrated into a nano-rectenna structure, allows for precise alignment and customization of the height-to-radius ratio to cover a wide spectral range from 400 nm to 1400 nm, minimizing parasitic capacitance and maximizing frequency response through quantum tunnelling effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If planar MIM diodes are used for rectification, then device simplicity is maintained, but frequency response is limited by parasitic capacitance to lower frequencies
Solution Approach 1:
The planar diode structure is segmented into multiple sharp-tip electrodes arranged in an array. Each tip provides a localized point-contact junction with minimal parasitic capacitance. The collective array maintains rectification functionality while achieving high frequency response through the combined effect of multiple low-capacitance junctions.
Solution Approach 2:
The invention transitions from a two-dimensional planar diode geometry to a three-dimensional array of sharp-tip electrodes. This dimensional change reduces the effective contact area at each junction point, minimizing parasitic capacitance while maintaining overall device functionality through the distributed array configuration.
2Speed
If sharp-tip point-contact diodes are used to reduce parasitic capacitance, then frequency response extends to hundreds of THz, but manufacturing precision requirements increase
Solution Approach 1:
The fabrication process employs dynamic control of the atomic force microscopy (AFM) cantilever to achieve precise tip formation and alignment. The cantilever is oscillated at its resonant frequency during fabrication, enabling real-time feedback control and dynamic adjustment of tip geometry and positioning to meet stringent alignment requirements.
Solution Approach 2:
Conventional mechanical alignment methods are replaced with atomic force microscopy (AFM)-based fabrication and characterization. The AFM system provides nanoscale precision in tip formation and positioning, substituting mechanical alignment procedures with a more precise probe-based approach that achieves the required sub-micron alignment accuracy.
3Ease of operation
If conventional diodes are used for rectification, then ease of operation is maintained, but rectification efficiency at infrared and visible frequencies is insufficient
Solution Approach 1:
The invention changes critical geometric parameters of the diode structure, specifically transitioning from planar contacts to sharp-tip point contacts with tip radii on the order of nanometers. This parameter change reduces junction capacitance and enhances quantum tunneling effects, enabling efficient rectification at infrared and visible frequencies while maintaining straightforward device operation.
Solution Approach 2:
The device employs composite material structures including metal-insulator-metal (MIM) junctions with carefully selected materials for each layer. The insulator layer uses materials with appropriate bandgaps for the target frequency range, while metal layers are chosen for their electrical properties and compatibility with sharp-tip fabrication, creating a composite structure optimized for both high-frequency operation and ease of use.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables high rectification efficiency and broadband capability, achieving operation up to hundreds of THz frequencies with preliminary evidence of 384 THz rectification, significantly surpassing previous efficiencies and extending the operational range into the visible spectrum.
Implementation Method 1
a plasmonic multi-tip nano-rectenna cell comprising a plurality of tapered, particularly conical tips coated with a plasmonic layer
Implementation Method 2
The Metal-Insulator-Metal (MIM) diode, operating based on quantum tunnelling, is the strongest candidate to extend rectification to hundreds of THz. Quantum tunnelling has been reported to be as fast as 1.8 fs allowing petahertz operation
Data Source
Figure 1a~2
Figure 3a~4b
Figure 5~6(b)
AI summary
A device for receiving and converting incident radiation into DC current, the device comprising at least one first conductor (10); a plurality of tapered antennas (20), each antenna (20) comprising a circular base (21) arranged on the at least one first conductor (10) and an apex (23), wherein a central axis (z) connecting the apex (23) to the centre of the base (21) is defined, and wherein each of said antennas comprises a tapered metallic structure arranged on the at least one first conductor (10), and a plasmonic coating layered on the metallic structure; at least one second conductor (30) arranged in front of the apexes (23) of the antennas (20); and an insulating layer (40) layered on the at least one second conductor (30) and interposed between the apexes (23) of the antennas (20) and the at least one second conductor (30). A plurality of point-contact junctions is formed, at which the apexes (23) of the antennas (20) contact the insulating layer (40); the central axes (z) of the antennas (20) are parallel to each other with an error smaller than 1 degree.