Unraveling the Interfacial Carrier Behavior in PtSe ₂ –MoSe ₂ Heterostructures: Insights from Combined Pump‐Probe Spectroscopy and Scanning Tunneling Microscopy

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.