MoSe₂/Au(111) Epitaxial Contact with Ultralow Defect Density: Native Fermi-Level Pinning and Work-Function Modulation

Guan-Hao Chen^1,2*, Cheng-Rong Hsing^3,4, Li-Syuan Lu^1,2, Po-Sen Mao^1,5, Pei-Yu Chuang⁶, Cheng-Maw Cheng^1,6, Ching-Ming Wei⁷, Chun-Liang Lin¹, Wen-Hao Chang^1,2,5

¹Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, Taiwan
²Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan
³Center for General Education, Chang Gung University, Taoyuan City, Taiwan
⁴Department of Artificial Intelligence, Chang Gung University, Taoyuan City, Taiwan
⁵Research Center for Critical Issues, Academia Sinica, Tainan, Taiwan
⁶National Synchrotron Radiation Research Center, Hsinchu, Taiwan
⁷Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan

* Presenter:Guan-Hao Chen, email:a0913635603@gmail.com

Fermi-level pinning (FLP) at metal–semiconductor interfaces has long hindered contact engineering in two-dimensional (2D) transition metal dichalcogenides. While theory attributes intrinsic FLP to metal-induced gap states and interfacial dipoles, direct experimental isolation of these mechanisms has been challenging, and many reports instead implicate extrinsic defects as the dominant cause. To resolve this, we construct an ultralow-defect MoSe₂/Au(111) epitaxial junction by oxygen-free growth and, through combined scanning tunneling spectroscopy, field-emission resonance, and angle-resolved photoemission spectroscopy, directly observe robust FLP in the absence of apparent interfacial disorder—establishing its inherent nature at an ideal 2D–metal contact. Crucially, controlled selenium intercalation at the MoSe₂/Au(111) interface reversibly modulates the interfacial dipole, enabling work-function tuning and Fermi-level depinning. This clean platform disentangles intrinsic contact physics from defect effects and provides a practical route to band-alignment control via intercalation.

Keywords: Fermi-level pinning , Oxygen-free growth, Ultralow defect density, Interface dipole, Intercalation