Interfacial charge transfer-mediated Fermi level pinning in MBE-grown 2D 2H-MoSe₂/2H-MoTe₂ heterostructures

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Molybdenum diselenide (MoSe2) and molybdenum ditelluride (MoTe2) heterostructures show promise for field-effect transistors (FETs) and near-infrared (NIR) optoelectronics due to tunable photoresponsivity and electrical properties.
• Interfacial processes in these heterostructures limit band tunability and carrier dynamics, posing challenges for device engineering.

Purpose of the Study:

• To investigate the interfacial effects in scalable, layer-by-layer grown trilayer MoSe2/MoTe2 heterostructures.
• To understand how interfacial bonding modifications influence band alignment and carrier transport.

Main Methods:

• Scalable, layer-by-layer growth of MoSe2/MoTe2 heterostructures via molecular beam epitaxy (MBE) on a SiO2 substrate.
• Angle-resolved X-ray photoelectron spectroscopy (AR-XPS) with tunable probing depth to analyze interfacial bonding and electronic structure.

Main Results:

• Identified interfacial Te migration and formation of Mo-Se-Te bonds.
• Observed asymmetric energy level shifts and Fermi level pinning (~0.58 eV above valence band edge on MoTe2 side).
• Anomalous upshift of MoSe2 valence band maximum and reduced hole injection barrier.

Conclusions:

• Interfacial interactions critically govern the band alignment of ultrathin transition metal dichalcogenide (TMDC) heterostructures.
• Site-specific interfacial processes induce deviations from predicted band alignment, impacting device performance.
• Findings provide insights for advancing nanoelectronic and optoelectronic devices through heterostructure band engineering.