Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Quantum effects bridge the gap

27.10.2014

Quantum effects in nanometer-scale metallic structures provide a platform for combining molecular electronics and plasmonics

Plasmonic devices combine the ‘super speed’ of optics with the ‘super small’ of microelectronics. These devices exhibit quantum effects and show promise as possible ultrafast circuit elements, but current material processing limits this potential. Now, a team of Singapore-based researchers has used a new physical process, known as quantum plasmonic tunneling, to demonstrate the possibility of practical quantum plasmonic devices(1).


An electron nanoprobe (yellow) placed near the functionalized silver nanoparticles measured plasmon-assisted quantum tunneling at terahertz frequencies.

© 2014 Shu Fen Tan, National University of Singapore

Tunneling is an intriguing aspect of quantum mechanics whereby a particle is able to pass through a classically insurmountable barrier. Theoretically, quantum plasmonic tunneling is only noticeable when plasmonic components are very closely spaced — within half a nanometer or less. However, researchers from the A*STAR Institute of Materials Research and Engineering, the A*STAR Institute of High Performance Computing and the National University of Singapore were able to observe quantum effects between materials spaced more than one nanometer apart.

They investigated the tunneling of electrons across a gap between two nanoscale cubes of silver coated with a monolayer of molecules. High-resolution transmission electron microscopy showed that these nanocubes self-assembled into pairs. The separation, and hence the tunneling distance, between the nanoparticles could be controlled by the choice of surface molecule — between 0.5 and 1.3 nanometers in the cases tested.

The monolayer of molecules had an another function — to provide molecular electronic control over the frequency of the oscillating tunnel current, which could be tuned between 140 and 245 terahertz (1 terahertz = 1012 hertz), as was shown by monochromated electron energy-loss spectroscopy.

Theoretical predictions, supported by experimental results, confirmed the nature of the plasmon-assisted tunnel currents between the silver cubes. “We show that it is possible to shine light onto a small system of two closely spaced silver cubes and generate a tunnel current that oscillates very rapidly between these silver electrodes,” explains A*STAR researcher Michel Bosman. “The oscillation is several orders of magnitude faster than typical clock speeds in microprocessors, which currently operate in the gigahertz (= 109 hertz) regime.” At the same time, the results also demonstrate the possibility of terahertz molecular electronics.

Two factors contributed to the success of the experiments. First, the nanocubes had atomically flat surfaces, maximizing the tunneling surface area between the two nanoparticles. Second, the molecule-filled gap increased the rate of tunneling, making it possible to measure plasmon-assisted quantum tunneling.

“We will now use different molecules in the tunnel gap to find out how far the tunnel currents can be carried, and in what range we can tune the oscillation frequency,” says Bosman.

Reference
(1) Tan, S. F., Wu, L., Yang, J. K. W., Bai, P., Bosman, M. & Nijhuis, C. A. Quantum plasmon resonances controlled by molecular tunnel junctions. Science 343, 1496–1499 (2014).

Associated links

A*STAR Research | Research SEA News
Further information:
http://www.research.a-star.edu.sg
http://www.researchsea.com

More articles from Physics and Astronomy:

nachricht Climate cycles may explain how running water carved Mars' surface features
02.12.2016 | Penn State

nachricht What do Netflix, Google and planetary systems have in common?
02.12.2016 | University of Toronto

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

Im Focus: Molecules change shape when wet

Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water

In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...

Im Focus: Fraunhofer ISE Develops Highly Compact, High Frequency DC/DC Converter for Aviation

The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.

Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

UTSA study describes new minimally invasive device to treat cancer and other illnesses

02.12.2016 | Medical Engineering

Plasma-zapping process could yield trans fat-free soybean oil product

02.12.2016 | Agricultural and Forestry Science

What do Netflix, Google and planetary systems have in common?

02.12.2016 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>