Gigahertz frame rate imaging of charge-injection dynamics in a molecular light source

TL;DR

This paper demonstrates gigahertz frame rate imaging of charge-injection dynamics in a molecular light source using scanning tunneling microscopy induced luminescence, revealing sub-nanosecond electron capture processes.

Contribution

It introduces a novel method to image molecular emitters and their charge dynamics at gigahertz frame rates with sub-nanosecond resolution.

Findings

Charge capture occurs in the low-nanosecond regime.

Imaging reveals fixed emitter location with tip-modified charge injection.

Method extends to fundamental processes like exciton diffusion.

Abstract

Light sources on the scale of single molecules can be addressed and characterized on their proper sub-nanometer scale by scanning tunneling microscopy induced luminescence (STML). Such a source can be driven by defined short charge pulses while the luminescence is detected with sub-nanosecond resolution. We introduce an approach to concurrently image the molecular emitter, which is based on an individual defect, with its local environment along with its luminescence dynamics at a resolution of a billion frames per second. The observed dynamics can be assigned to the single electron capture occurring in the low-nanosecond regime. While the emitter's location on the surface remains fixed, the scanning of the tip modifies the energy landscape for charge injection to the defect. The principle of measurement is extendable to fundamental processes beyond charge transfer like exciton diffusion.