2D Cd metal contacts via low-temperature van der Waals epitaxy towards high-performance 2D transistors.

Abstract

Two-dimensional (2D) semiconductors hold great promise for future electronics, yet the fabrication of clean ohmic electrical contacts remains a key challenge. Traditional lithography and metallization processes often introduce interfacial disorder, and recently developed electrode-transfer-based techniques are difficult to implement without contaminating the interfaces between 2D crystals and metals. Here, we demonstrate a low-temperature chemical vapor deposition (CVD)-based van der Waals (vdW) epitaxy method to grow 2D metal (Cd) electrodes, eliminating lithography, deposition, or transfer processes and enabling the damage-free integration of 2D semiconductors. This thermodynamic integration strategy significantly mitigates the interfacial disorder and metal-induced gap states (MIGS), leading to low contact resistance (R_C) and near-zero barrier ohmic contacts. Cd-MoS₂ field-effect transistors (FETs) exhibit R_C down to 70-100 Ω·μm, on-state current densities up to 942 μA/μm, on/off ratios exceeding 10⁸, and mobilities up to 160 cm²V^-1s^-1. These results position vdW epitaxially grown 2D metals as a promising contact technology for next-generation electronics beyond silicon.