Nanoplasmonics is an important emerging research area in technologies, such as energy conversion using photovoltaic devices and hydrogen sensing using Pd nanoparticles. So far, plasmon excitations are only known to exist at the interface between two different dielectric media, such as two solids or at solid-vacuum surfaces. There has been no evidence for the presence of a plasmon at a solid-liquid interface. This paper presents results on the existence and nature of the plasmon resonance between a semiconducting solid and a liquid metal, investigated in a transmission electron microscope having sub-eV and sub-$\AA$ resolutions. The results are compared with calculations of the plasmon based on dielectric theory and are corroborated with energy-filtered imaging analyses. The unique plasmon resonance observed at the solid-liquid interface provides new insight into the behavior of plasmons in research areas from biomedical imaging to liquid crystals, including the technologies mentioned above.

• Received 9 January 2012

DOI:https://doi.org/10.1103/PhysRevB.85.195305