Point-projection microscopy of nano-localized photoemission currents at sub-40 femtosecond time scales

TL;DR

This paper demonstrates femtosecond point-projection microscopy (fs-PPM) as a high-resolution technique for visualizing ultrafast charge carrier dynamics in nanomaterials, achieving sub-40 femtosecond temporal resolution.

Contribution

It benchmarks fs-PPM's capability to image ultrafast charge dynamics at nanoscales, revealing detailed electron and hole behaviors in silver nanowires.

Findings

Achieved 33 fs temporal resolution of photoelectron response.

Visualized space-charge driven electron motion at sub-100 nm scales.

Observed positive charging and electron-hole dynamics post-photoemission.

Abstract

Femtosecond point-projection microscopy (fs-PPM) is an electron microscopy technique that possesses a combination of high spatio-temporal resolution and sensitivity to local electric fields. This allows it to visualize ultrafast charge carrier dynamics in complex nanomaterials. We benchmark the capability of the fs-PPM technique by imaging the ultrafast dynamics of charge carriers produced by multiphoton ionization of silver nanowires. The space-charge driven motion of photoelectrons is followed on \mbox{sub-100}\,nm length scales, while the dynamics are captured on 30-100 fs time scales. The build-up of electron holes in the silver nanowires following photoelectron ejection, i.e. positive charging, has also been observed. The fastest observed photoelectron temporal response is 33 fs (FWHM), which represents an upper estimate of the instrument response function and is consistent with an expected electron wavepacket duration of 13 fs based on simulations.