A brief review: Ultrafast electron diffractive voltammetry: General formalism and applications

TL;DR

This paper introduces a comprehensive formalism for ultrafast diffractive voltammetry, demonstrating its application in studying ultrafast surface charge dynamics and hot electron behavior at nanostructured interfaces.

Contribution

It develops a general framework for ultrafast diffractive voltammetry and explores its application to various surface charge processes and electron dynamics.

Findings

Photoinduced surface charging occurs at multiple levels during femtosecond laser excitation.

Photoemission contributes a long decay tail to the voltammetry signal, prominent on nanosecond timescales.

Ultrafast voltammetry mainly captures local charge transfer processes at interfaces.

Abstract

We present a general formalism of ultrafast diffractive voltammetry approach as a contact-free tool to investigate the ultrafast surface charge dynamics in nanostructured interfaces. As case studies, the photoinduced surface charging processes in oxidized silicon surface and the hot electron dynamics in nanoparticle-decorated interface are examined based on the diffractive voltammetry framework. We identify that the charge redistribution processes appear on the surface, sub-surface, and vacuum levels when driven by intense femtosecond laser pulses. To elucidate the voltammetry contribution from different sources, we perform controlled experiments using shadow imaging techniques and N-particle simulations to aid the investigation of the photovoltage dynamics in the presence of pho- toemission. We show that voltammetry contribution associated with photoemission has a long decay tail and plays a more visible role in the nanosecond timescale, whereas the ultrafast voltammetry are dominated by local charge transfer, such as surface charging and molecular charge transport at nanostructured interfaces. We also discuss the general applicability of the diffractive voltammetry as an integral part of quantitative ultrafast electron diffraction methodology in researching different types of interfaces having distinctive surface diffraction and boundary conditions.