January 31, 2020
Keio University
Kana Yamagiwa (who completed her master's degree in 2018) of the Graduate School of Science and Technology, Keio University, Professor Atsushi Nakajima of the Faculty of Science and Technology, and Project Associate Professor Masahiro Shibuta (at the time of the research; currently a Project Lecturer at Osaka City University) have revealed that by using the plasmonic response of nanoclusters composed of several tens of silver atoms, it is possible to observe the energy propagation of waves induced beneath a material's surface (at a "buried interface"), which was previously unobservable.
In recent years, as optical communication technology and optical energy utilization have become important for high-speed communication and the development of energy resources, research and development combined with nanotechnology has been actively pursued. When light is irradiated onto a metal surface, surface plasmon polaritons (SPPs) are generated, and the phenomenon of their propagation is expected to have applications from the perspective of increasing the efficiency of photonic nanodevices such as plasmonic optical circuits and plasmonic lasers, and photoelectric conversion devices such as solar cells. Visualizing how the propagation of these SPPs changes over time is extremely important for precisely controlling their velocity and spatial extent, as well as for improving propagation efficiency. Therefore, the development of methods to visualize SPPs has been strongly desired.
This research group conducted the visualization and evaluation of the physical properties of SPPs using a photoemission electron microscope (PEEM). In particular, they worked on developing a method to observe SPPs propagating at an interface where a metal surface is covered by a molecular film, which is considered particularly difficult to visualize. As a result, by slightly depositing silver nanoclusters as a sensitizer on the outermost surface, they succeeded in visualizing the SPPs at the "buried interface" beneath the molecular film, which were previously unobservable. These results are considered to be of high value as a fundamental technology for device applications using plasmonic response. The results of this research were published in the American Chemical Society's journal "ACS Nano" on January 30, 2020 (US time).
Please see below for the full press release.