Unlocking cooperative Schottky barrier modulation via weakening Fermi-level pinning in composite–metal–MoS2 heterostructures

Abstract

Metal/semiconductor contacts critically determine the performance of two-dimensional (2D) MoS2-based devices. Conventional three-dimensional metals (3DMs) induce strong chemical interactions with MoS2, resulting in interface states and pronounced Fermi-level pinning (FLP), which limits Schottky barrier height (SBH) tunability. 2D metals (2DMs), in contrast, form van der Waals (vdW) interfaces with MoS2, suppressing FLP, but often lack process compatibility. Here, we employ first-principles density functional theory to investigate SB formation in composite 3DM/2DM/mMoS2 heterostructures, comparing 3DM/mMoS2, 2DM/mMoS2, and 3DM/2DM/mMoS2 systems. Our results show that inserting a 2DM layer partially mitigates FLP, increasing SBH sensitivity to metal work function (WM). Analysis of the layer-resolved surface electrostatic potential differences (ΔV) and charge density difference reveals that the dominant contribution to ΔV originates from the 3DM–2DM interface, while the 2DM–mMoS2 vdW interface preserves semiconducting characteristics. Consequently, SBH modulation in 3DM/2DM/mMoS2 heterostructures arises from a dual-interface cooperative mechanism, where work function alignment at the vdW interface and surface electrostatic potential differences at the 3DM–2DM interface jointly govern Schottky barrier formation. This mechanism is further supported by correlations between interfacial distance, work function, and surface electrostatic potential differences. Our work elucidates the atomic-scale origin of Schottky barrier modulation in composite metal/mMoS2 heterostructures and provides a viable, process-compatible strategy for engineering low-resistance contacts in MoS2 devices.