Surface Plasmon Assisted Control of Hot-Electron Relaxation Time

TL;DR

This study demonstrates that surface plasmons can significantly slow down hot electron relaxation times in gold thin films, offering a new way to control hot carrier dynamics in optoelectronic devices.

Contribution

It provides the first systematic experimental evidence that propagating surface plasmons influence hot carrier relaxation times in gold thin films.

Findings

Surface plasmons slow hot electron relaxation in gold.

Local electric fields affect hot carrier distribution.

Control of hot carrier lifetime is possible across optical frequencies.

Abstract

Surface plasmon mediated hot carrier generation is widely utilized for the manipulation of the electron-photon interactions in many types of optoelectronic devices including solar cells, photodiodes, and optical modulators. A diversity of plasmonic systems such as nanoparticles, resonators, and waveguides have been introduced to enhance hot carrier generation; however, the impact of the propagating surface plasmons on hot carrier lifetime has not been clearly demonstrated. Here, we systematically study the hot carrier relaxation in thin film gold (Au) samples under surface plasmon coupling with the Kretschmann configuration. We observe that the locally confined electric field at the surface of the metal significantly affects the hot carrier distribution and electron temperature, which results in a slowing of the hot electrons relaxation time, regardless of the average value of the absorbed power in the Au thin film. This result could be extended to other plasmonic nanostructures, enabling the control of hot carrier lifetimes throughout the optical frequency range.