Singapore Researchers Use Electron Microscopy to Link Plasmonics with Molecular Electronics

FEI has congratulated its customers, National University of Singapore, Singapore University of Technology and Design, and the A*STAR institutes: Institute of High Performance Computing and Institute of Materials Research and Engineering, on their recent discovery of quantum plasmonic tunneling ¹—a quantum-mechanical effect where electrons rapidly oscillate across very closely-spaced metal structures. Using a Titan™ scanning/transmission electron microscope (S/TEM), the scientists were able to not only observe this new phenomenon directly, but also control the frequency of the tunneling currents by placing single layers of different molecules between the closely-spaced metal particles. The speed of the switching will directly depend on the nature of the molecules used.

 “In our research, we were able to demonstrate that the rapid current oscillations could take place over distances larger than a nanometer, which, although extremely small, opens up possibilities for new technological applications,”  said Dr Michel Bosman, Institute of Materials Research and Engineering, A*STAR, Singapore, a researcher and co-author on the project.

Surface plasmons in metal particles can be introduced by simply shining light of the right color on them. By using the researchers’ approach, incoming light will then produce the small tunneling currents between the nearby metal particles. In effect, tiny electrical circuits are made that operate at enormously high speeds. Today’s electrical circuits can operate up to GHz frequencies, but due to design issues, this is close to their inherent speed limit at room temperature. In order for devices to work faster, entirely new circuit designs are required. The research presented here shows a possible route for such optical circuits, by light-generated tunneling currents with operation speeds tens of thousands of times faster than today’s microprocessors.

Trisha Rice, vice president and general manager of Materials Science for FEI, comments, “This is incredible work being done by these researchers in Singapore, using the high-energy resolution of a monochromated Titan S/TEM to directly observe and control a quantum plasmonic tunneling event. Congratulations on this achievement and we look forward to learning of new and exciting results in this area.”

1.Science 28^th March  https://ilmt.co/PL/rW63.  “Quantum Plasmon Resonances Controlled by Molecular Tunnel Junctions,” Shu Fen Tan et al, Science 343, 1496 (2014); DOI 10.1126/science. 1248797.