Thermally oxidized 2D TaS2 as a high-κ gate dielectric for MoS2 field-effect transistors

Abstract

We report a new approach to integrating high-κ dielectrics in both bottom- and top-gated MoS2 field-effect transistors (FETs) through thermal oxidation and mechanical assembly of layered two-dimensional (2D) TaS2. Combined x-ray photoelectron spectroscopy (XPS), optical microscopy, atomic force microscopy (AFM), and capacitance–voltage (C–V) measurements confirm that multilayer TaS2 flakes can be uniformly transformed to Ta2O5 with a high dielectric constant of ~15.5 via thermal oxidation, while preserving the geometry and ultra-smooth surfaces of 2D TMDs. Top-gated MoS2 FETs fabricated using the thermally oxidized Ta2O5 as gate dielectric demonstrate a high current on/off ratio approaching 106, a subthreshold swing (SS) down to 61 mV/dec, and a field-effect mobility exceeding 60 cm2 V−1 s−1 at room temperature, indicating high dielectric quality and low interface trap density.