Watching charge separation in nanoantennas by ultrafast point-projection electron microscopy

TL;DR

This paper demonstrates a novel ultrafast electron microscopy technique with 20-nm spatial and 25-fs temporal resolution, enabling real-time observation of charge dynamics in nanostructures.

Contribution

It introduces an ultrafast electron source based on plasmon nanofocusing integrated into a point-projection electron microscope for the first time.

Findings

Achieved 20-nm spatial resolution in electron motion imaging.

Demonstrated 25-fs temporal resolution in charge dynamics.

Observed ultrafast photoemission from plasmonic nanoantennas.

Abstract

Watching the motion of electrons on their natural nanometre length- and femtosecond time scales is a fundamental goal and an open challenge of contemporary ultrafast science. Optical techniques and electron microscopy currently mostly provide either ultrahigh temporal or spatial resolution, yet, microscopy techniques with combined space-time resolution need further development. Here we create an ultrafast electron source by plasmon nanofocusing on a sharp gold taper and implement this source in an ultrafast point-projection electron microscope. This source is used, in an optical pump - electron probe experiment, to study ultrafast photoemission from a nanometer-sized plasmonic antenna. We show that the real space motion of the photoemitted electrons and residual holes in the metal is probed with 20-nm spatial resolution and 25-fs time resolution. This is a step forward towards time-resolved microscopy of electronic motion in nanostructures.