Thermally oxidized 2D TaS 2 as a high- κ gate dielectric for MoS 2 field-effect transistors

We report a new approach to integrating high- κ dielectrics in both bottom- and top-gated MoS 2 field-effect transistors (FETs) through thermal oxidation and mechanical assembly of layered two-dimensional (2D) TaS 2 . Combined x-ray photoelectron spectroscopy (XPS), optical microscopy, atomic force microscopy (AFM), and capacitance–voltage ( C – V ) measurements confirm that multilayer TaS 2 flakes can be uniformly transformed to Ta 2 O 5 with a high dielectric constant of ~15.5 via thermal oxidation, while preserving the geometry and ultra-smooth surfaces of 2D TMDs. Top-gated MoS 2 FETs fabricated using the thermally oxidized Ta 2 O 5 as gate dielectric demonstrate a high current on/off ratio approaching 10 6 , a subthreshold swing (SS) down to 61 mV/dec, and a field-effect mobility exceeding 60 cm 2 V −1 s −1 at room temperature, indicating high dielectric quality and low interface trap density.