Ultrafast Dynamics of Defect-Assisted Auger Process in PdSe2 Films: Synergistic Interaction between Defect Trapping and Auger Effect.

ABSTRACT

By using optical pump and terahertz probe spectroscopy, we have investigated the photocarrier dynamics in PdSe2 films with different thicknesses. 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 that has typical lifetime of 7.3 ps decreasing with the layer thickness. Interestingly, the relaxation times for both fast and slow components 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 a 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 the Auger process and defects in two-dimensional semiconductors.