Ultrafast Dynamics of Defect-Assisted Auger process in PdSe2 films: Synergistic Interaction Between Defect Trapping and Auger Effect

TL;DR

This study investigates the ultrafast carrier relaxation in PdSe2 films, revealing defect-assisted Auger processes dominate dynamics, with layer-dependent lifetimes influenced by defect density, independent of fluence and temperature.

Contribution

It introduces a defect-assisted Auger model for 2D PdSe2, explaining layer-dependent carrier lifetimes and the interplay between defects and Auger effects in ultrafast dynamics.

Findings

Fast relaxation component of 2.5 ps is layer-thickness independent.

Slow component of 7.3 ps decreases with layer thickness.

Relaxation times are independent of pump fluence and temperature.

Abstract

Strong Coulomb interactions in two-dimensional systems, together with quantum confinement, make many-body processes particularly effective for carrier dynamics, which plays a crucial role in determining carrier lifetime, photoconductivity, and emission yield of the materials. Hereby, by using optical pump and terahertz probe spectroscopy, we have investigated the photocarrier dynamics in the PdSe2 films with different thickness. The experimental results reveal that the photocarrier relaxation consists of two components: a fast component of 2.5 ps that shows the layer-thickness independence, and a slow component has typical lifetime of 7.3 ps decreasing with the layer thickness. Surprisingly, the relaxation times for both fast and slow components are exhibited both pump fluence and temperature independence, which suggests that synergistic interactions between defect trapping and Auger effect dominate the photocarrier dynamics in PdSe2 films. A model involving defect-assisted Auger process is proposed, which can reproduce the experimental results well. The fitting results reveal that the layer dependent lifetime is determined by the defect density rather than carrier occupancy rate after photoexcitation. Our results underscore the interplay between Auger process and defects in two-dimensional semiconductors.