Decrypting material performance by wide-field femtosecond interferometric imaging of energy carrier evolution

TL;DR

This paper introduces Femto-iSCAT, a highly sensitive ultrafast imaging technique combining femtosecond pump-probe and interferometric scattering microscopy to visualize energy carrier dynamics at the nanoscale.

Contribution

The study develops a novel interferometric imaging method that significantly enhances contrast, enabling direct visualization of energy carriers' spatiotemporal evolution in complex materials.

Findings

Enhanced transient image contrast by over 100 times.

Successfully visualized energy carrier transport at interfaces.

Revealed structure-dependent carrier dynamics in semiconductors.

Abstract

Energy carrier evolution is crucial for material performance. Ultrafast microscopy has been widely applied to visualize the spatiotemporal evolution of energy carriers. However, direct imaging of small amounts of energy carriers on nanoscale remains difficult due to extremely weak transient signals. Here we present a method for ultrasensitive and high-throughput imaging of energy carrier evolution in space and time. This method combines femtosecond pump-probe techniques with interferometric scattering microscopy (iSCAT), named Femto-iSCAT. The interferometric principle and unique spatially-modulated contrast enhancement increase the transient image contrast by >2 orders of magnitude and enable the exploration of new science. We address three important and challenging problems: transport of different energy carriers at various interfaces, heterogeneous hot electron distribution and relaxation in single plasmonic resonators, and distinct structure-dependent edge state dynamics of carriers and excitons in optoelectronic semiconductors. Femto-iSCAT holds great potential as a universal tool for ultrasensitive imaging of energy carrier evolution in space and time.