Electron Imaging of Nanoscale Charge Distributions Induced by Femtosecond Light Pulses

TL;DR

This paper uses electron imaging to study nanoscale surface charging caused by femtosecond light pulses, revealing charge dynamics and proposing methods to mitigate charging effects in electron microscopy.

Contribution

It introduces a quantitative approach to image and analyze light-induced surface charging and its dynamics at the nanoscale.

Findings

Quantitative extraction of light-induced electrostatic potential.

Observation of charging dynamics on femtosecond timescales.

Mitigation of sample charging through simultaneous optical illumination.

Abstract

Surface charging is a phenomenon ubiquitously observable in in-situ transmission electron microscopy of non-conducting specimens as a result of electron beam/sample interactions or optical stimuli and often limits the achievable image stability and spatial or spectral resolution. Here, we report on the electron-optical imaging of surface charging on a nanostructured surface following femtosecond-multiphoton photoemission. By quantitatively extracting the light-induced electrostatic potential and studying the charging dynamics on the relevant timescales, we gain insights into the details of the multi-photon photoemission process in the presence of a background field. We study the interaction of the charge distribution with the high-energy electron beam and secondary electrons and propose a simple model to describe the interplay of electron- and light-induced processes. In addition, we demonstrate how to mitigate sample charging by simultaneous optical illumination of the sample.