Quantum Plasmon Resonances Controlled by Molecular Tunnel Junctions

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Asst Prof Christian Nijhuis from the Department of Chemistry, has collaborated with Dr Michel Bosman from the Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR) and Dr Bai Ping Institute of High Performance Computing (IHPC), A*STAR, to design and fabricate ultra-fast electrical circuits that operate using the new physical process, quantum plasmonic tunneling, at terahertz frequencies to potentially bypass the inherent speed limit of copper-based interconnects.

Asst Prof Nijhuis and his team are the first to observe the quantum plasmonic tunneling effects directly. Before their research, state-of-the-art nanoelectronic devices operate at length scales that are much smaller than that of visible light, making it difficult to combine the ultra-fast properties of photonic elements with nano-scale electronics to be able to observe the quantum plasmonic tunneling effects directly.

It is shown for the first time, experimentally and theoretically, that very fast-switching at optical frequencies are indeed possible in molecular electronic devices. In addition, by simply changing the molecules in the device, the frequency of the circuits can be altered in the hundreds of terahertz regime. This novel discovery by the multidisciplinary research team opens up possibilities for real applications such as high speed electronics at terahertz frequencies.

To further their research, Asst Prof Nijhuis and his team are looking into resolving challenges such as the integration of these devices into real electronic circuits.

This study was funded by the Singapore National Research Foundation (NRF) of Singapore and has been published in the findings were published in Science on 28 March 2014.

 The figure above shows the two plasmonic resonators (silver nanocubes) bridged by a layer of molecules with a length of 0.5 nm. A focused electron beam (in yellow) was used to characterise the structures and to probe the optical properties.