Inherent Fermi-Level Pinning and Work-Function Modulation at the Ultralow-Defect MoSe₂/Au(111) Epitaxial Junction

Fermi-level pinning (FLP) at metal–semiconductor interfaces remains a central obstacle to contact engineering in two-dimensional (2D) transition metal dichalcogenides. Although theory attributes intrinsic FLP to metal-induced gap states and interfacial dipoles [1], isolating these mechanisms experimentally has been challenging, and previous representative works for depinning reports have instead implicated extrinsic defects as a primary source [2,3]. Here, we resolve this ambiguity by realizing an ultralow-defect epitaxial junction between monolayer MoSe₂ and Au(111). Combining scanning tunneling spectroscopy, field-emission resonance, and angle-resolved photoemission spectroscopy, we directly observe robust FLP in the absence of apparent interfacial disorder, thereby establishing its inherent nature at an ideal 2D–metal contact. Furthermore, we demonstrate that controlled selenium intercalation at the MoSe₂/Au(111) interface provides a reversible handle to modulate the interfacial dipole and local work function, enabling Fermi-level depinning and systematic band-alignment tuning. This clean platform disentangles intrinsic contact physics from defect effects and introduces an intercalation-based route to work-function engineering in 2D electronics.



References

[1] C. Gong, et al. Nano Lett. 14, 1714–1720 (2014).

[2] Y. Liu, et al. Nature 557, 696–700 (2018).

[3] Y. Wang, et al. Nature 568, 70–74 (2019).