Unraveling the Interfacial Carrier Behavior in PtSe₂-MoSe₂ Heterostructures: Insights from Combined Pump-Probe...

Interfacial carrier behavior is vital for modifying the optoelectronic performance of 2D materials with atomical thickness, yet understanding exciton dynamics within hetero-phase heterojunctions at the nanoscale remains elusive. Here, carrier dynamics at the interface in molecular beam epitaxy grown 1T PtSe₂-1H MoSe₂ heterostructures are revealed by ultrafast pump-probe spectroscopy, and the corresponding mechanisms are studied by combining scanning tunneling microscopy/spectroscopy (STM/STS). The difference in exciton lifetimes and signal intensities in the heterostructures at the energies larger and narrower than the bandgap of MoSe₂ demonstrates both electrons and holes transfer at the interface of PtSe₂ and MoSe₂ monolayers. Such bipolar transfer is interpreted through both the type-I (lateral) and type-II (vertical) band alignments revealed by STS measurements across the heterojunctions interface. Besides, it also shows that the band alignment modification of in-plane heterojunctions by a specific conductive substrate can fairly alter the exciton dynamics at the interface. This work provides a comprehensive insight into the carrier dynamics in PtSe₂-MoSe₂ heterostructures with high spatial and temporal resolutions and may be beneficial for their design in optoelectronic devices.