A marriage of photonics and nanostructures could enable a huge leap in computer processing speed. A new technique using plasmonic tunneling has allowed researchers to create electrical circuits that operate at hundreds of terahertz – tens of thousands of times faster than today’s desktop computers. Assistant professor Dr. Christian A. Nijhuis of the National University of Singapore (NUS) and colleagues used two plasmonic resonators, bridged by a layer of molecules exactly one molecule thick, to create an element of a molecular electronic circuit. The layer of molecules switches on the quantum plasmonic tunneling effects, enabling the circuits to operate at terahertz frequencies. A focused electron beam (in yellow) was used to characterize the structures and probe the optical properties of two plasmonic resonators bridged by a layer of molecules with a length of 0.5 nm. Courtesy of Tan Shu Fen, National University of Singapore. “Our team is the first to observe the quantum plasmonic tunneling effects directly,” Nijhuis said. “This is also the first time that a research team has demonstrated theoretically and experimentally that very fast switching at optical frequencies are indeed possible in molecular electronic devices.” Dr. Michel Bosman of the Agency for Science, Technology and Research (A*STAR) used an advanced electron microscopy technique to visualize and measure the optoelectronic properties of the circuits with nanometer resolution. The measurements revealed the existence of the quantum plasmon mode and that its speed could be controlled by varying the molecular properties of the devices. Dr. Bai Ping, also of A*STAR, used quantum-corrected simulations to confirm that the quantum plasmonic properties could be controlled in the molecular electronic devices at terahertz frequencies. The new circuits could also be used to construct single-molecule detectors and may have implications for nanoscale optoelectronics and nonlinear optics, the researchers said. The study was funded by the National Research Foundation and A*STAR. The results are published in Science (doi: 10.1126/science.1248797). For more information, visit: www.nus.edu.sg