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

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. (letter)