Revisiting the Schottky-Mott Relation for Metal/Transition Metal Dichalcogenide Interfaces: The Role of Interface Dipoles
Chih-Piao Chuu, Shu-Jui Chang, Yu-Miin Sheu, Zih-Syuan Huang, Wei-Tung Liu, Po-Wei Chen, Sui-An Chou, Yu-Tung Lin, Chih-I Wu, Wen-Hao Chang, Chun-Liang Lin, H.-S. Philip Wong, Iuliana P. RaduAbstract
High contact resistance, stemming from Fermi-level pinning (FLP), is a bottleneck in the contact engineering of transition metal dichalcogenide (TMD)-based two-dimensional field-effect transistors (2DFETs). Our study re-examines the nature of FLP in 2D semiconductors, focusing on regimes where the material thickness is commensurate with the interface thickness. By combining first-principles calculations with experimental validation via ultraviolet photoelectron spectroscopy (UPS) and scanning tunneling spectroscopy (STS), we establish the metal effective work function (eWF) as a figure of merit for substantiating the Schottky-Mott relation. Our findings indicate that FLP is governed by both long-range dipole interactions and extended short-range Lennard-Jones potentials. This framework, in conjunction with the linear Schottky-Mott relation, improves predictive capabilities in contact engineering.