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On-Chip Molecular Electronic Plasmon Sources Based on Self-Assembled Monolayer Tunnel Junctions

Technology #16046n

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Researchers
Prof Christian Nijhuis
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Dr Tan Yan Ny
Manager (65)66012812
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US Patent Pending
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Tech Offer 16046N On-Chip Moleclar Electronic Plasmon Sources [PDF]

On-Chip Molecular Electronic Plasmon Sources Based on Self-Assembled Monolayer Tunnel Junctions

Market Need

Molecular electronic control over plasmons offers a promising route for on-chip integrated molecular-plasmonic devices for information processing and computing. To move beyond the currently available technologies, and to miniaturise the plasmonic devices, molecular electronic plasmon sources are needed. Conventional plasmon sources that rely on on-chip (nano) LEDs or other light sources such as laser diodes, silicon spheres, and single carbon nanotubes are bulky and face miniaturization challenges. Our plasmon sources operate at molecular length scales. Hence they are inherently smaller than conventional plasmon sources that rely on on-chip (nano) LEDs or other light sources. In addition, for the first time, we also show molecular electronic control of the plasmon intensity by changing the chemical structure of the molecules and by bias-selective excitation of plasmons using molecular diodes.

Solution

Prof. Christian Nijhuis from the department of Chemistry, National University of Singapore, has developed an on-chip molecular electronic plasmon sources based on self-assembled monolayer (SAM) tunnel junctions (STJs). The developed on-chip molecular electronic plasmon sources consist of tunnel junctions based on SAMs sandwiched between two metallic electrodes that excite localised plasmons and surface plasmon polaritons by tunnelling electrons. The plasmons originate from single, diffraction-limited spots within the junctions, follow power-law distributed photon statistics, and have well-defined polarisation orientations. The structure of the SAM and the applied bias influence the observed polarisation. We also show molecular electronic control of the plasmon intensity by changing the chemical structure of the molecules and by bias-selective excitation of plasmons using molecular diodes. The developed molecular electronic plasmon sources work at quantum mechanical tunnelling time scale, which is 1 million times faster than conventional semiconductor devices. In addition, they work at low voltages and low current, resulting in low power consumption. Also, for the first time, molecular electronic control of plasmons is demonstrated: (i) Intrinsic plasmonic source size at single molecule scale (much smaller than conventional semiconductor devices), (ii) bias selective excitation of plasmons with molecular diode (iii) controlled plasmon intensity and polarization with molecular electronic properties.


Figure 1. The SAM-based tunnel junctions. a, A schematic of the STJ with the Ga2O3/EGaIn top electrode constrained in PDMS and an ultra-flat AuTS bottom electrode supporting SAMs. An optical adhesive (OA) was used to glue the AuTS on the glass substrate. b, Illustration of the STJ with a SAM of SCn (left) and S-OPE-Fc (right), where the blue arrow indicate the tunnelling direction along the molecular backbone, α is the tilt angle of the SAM, and d is the tunnelling barrier width.


Figure 2. Molecular electronic excitation of plasmons. a,b, The real plane (a) and back focal plane (b) images of plasmons excited in a STJ with a SC12 SAM on a 50 nm AuTS film at -1.8 V. The image acquisition time is 2 minutes. Modes I and II indicate the SPP modes with k =1.01 and k =1.47 respectively. In b, the inner dashed circle indicates the critical angle and the outer dashed circle indicates the numerical aperture (NA=1.49) of the oil objective.



Figure 3. a, Corresponding spectra of plasmons excited at the same conditions as in Figure 2. The vertical lines indicate the corresponding wavelength with energy eVbias. b, Molecular length dependency of the current density J and the plasmon intensity density at -1.8 V. Here, SAMs of SCn molecules (n = 10, 12, 14, and 16) were incorporated into the junctions.


Application and advantages

Potential application is for optoelectronics and biosensors.

The advantages are:

  • Direct plasmon excitation via through molecular bond tunneling without electron-hole pair generation
  • Easy coupling with other circuit components.
  • Easy fabrication process, high throughput.
  • Molecular electronic control over plasmon excitation ie. Intrinsic plasmonic source size at single molecule scale (much smaller than conventional semiconductor devices), bias selective excitation of plasmons with molecular diode, controlled plasmon intensity and polarization with molecular electronic properties.

Keywords

Molecular Electronic, Plasmon, Source, computing, molecular tunnel junction

ILO Reference: 16046N

Patent Status: Patent pending

Principal Inventor

Prof Christian Nijhuis christian.nijhuis@nus.edu.sg

Get in touch with the Technology Manager

Tan Yan Ny

Email:  tan.yan.ny@nus.edu.sg

Phone: +65-66012812