Partially Oxidized TaS 2 as a High-Quality Gate Stack for Two-Dimensional Transistors

Two-dimensional (2D) semiconductors are promising channel materials for next-generation transistors, but the integration of gate stacks with clean interfaces remains challenging. Here, we demonstrate that a high-quality gate stack, composed of a van der Waals gate metal and high-κ dielectric, could be prepared via partial oxidation of layered tantalum disulfide (TaS₂), and integrated with 2D semiconductors through van der Waals assembly. This nondestructive and contamination-free process ensured atomically abrupt and impurity-free interfaces of the gate-electrode/dielectric and dielectric/semiconductor. The chemically converted TaO_x displayed dielectric properties with a high dielectric constant of 28.6 and a breakdown field of 5 MV/cm. Top-gated 2D MoS₂ FETs fabricated using the obtained TaO_x/TaS₂ heterostructure as gate stack exhibited an on/off current ratio over 10⁷, a subthreshold swing down to 61.7 mV/decade and a gate leakage current below 50 fA. We also show that the TaO_x/TaS₂ gate stack could be used to construct high-gain (>90) 2D complementary inverters.