Thermally Oxidized Two-dimensional TaS2 as a High-\k{appa} Gate Dielectric for MoS2 Field-Effect Transistors

TL;DR

This paper introduces a novel method for creating high-ppa dielectric layers from thermally oxidized 2D TaS2, enabling high-performance MoS2 FETs with excellent switching characteristics.

Contribution

It presents a new technique to convert layered TaS2 into high-ppa Ta2O5 dielectrics while maintaining surface quality for improved 2D transistor performance.

Findings

High-ppa Ta2O5 dielectric with ppa  15.5 achieved via thermal oxidation.

Top-gated MoS2 FETs show mbda  10^6 on/off ratio and 61 mV/dec subthreshold swing.

FETs exhibit mobility exceeding 60 cm^2V s at room temperature.

Abstract

We report a new approach to integrating high-\k{appa} dielectrics in both bottom- and top-gated MoS2 field-effect transistors (FETs) through thermal oxidation and mechanical assembly of layered twodimensional (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 cm2V-1 s-1 at room temperature, indicating high dielectric quality and low interface trap density.