Photothermionic Effect-Assisted Ultrafast Charge Transfer in NbS₂/MoS₂ Heterostructure

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Two-dimensional (2D) van der Waals heterostructures (vdW HSs) from transition metal dichalcogenides (TMDCs) are leading in optoelectronics.
• Research on interlayer charge transfer has focused on Type II HSs, with less attention on metal-semiconductor (MS) vertical HSs for photodetectors.

Purpose of the Study:

• To investigate ultrafast interlayer charge transfer in NbS2/MoS2 heterostructures.
• To explore the photothermionic effect's role in charge transfer and carrier generation.
• To advance photodetector technology using 2D vdW HSs.

Main Methods:

• Femtosecond transient absorption spectroscopy.
• First-principles calculations.
• Fabrication of NbS2/MoS2 heterostructures.

Main Results:

• Experimental observation of photothermionic effect-assisted ultrafast interlayer charge transfer (within 500 fs) from NbS2 to MoS2.
• Demonstrated supplementary carrier generation in the visible spectrum when excited with infrared light below the MoS2 bandgap (1030 and 1500 nm).
• Ignored Schottky barrier height in the analysis.

Conclusions:

• 2D NbS2-semiconductor heterostructures offer a platform for low contact resistance and broadband photocarrier generation.
• This work marks a significant advancement in 2D optoelectronics and light harvesting.
• The findings pave the way for novel photodetector designs.