Ionic-Liquid Gating in Two-Dimensional TMDs: The Operation Principles and Spectroscopic Capabilities

Abstract

Ionic-liquid gating (ILG) is able to enhance carrier densities well above the achievable values in traditional field-effect transistors (FETs), revealing it to be a promising technique for exploring the electronic phases of materials in extreme doping regimes. Due to their chemical stability, transition metal dichalcogenides (TMDs) are ideal candidates to produce ionic-liquid-gated FETs. Furthermore, as recently discovered, ILG can be used to obtain the band gap of two-dimensional semiconductors directly from the simple transfer characteristics. In this work, we present an overview of the operation principles of ionic liquid gating in TMD-based transistors, establishing the importance of the reference voltage to obtain hysteresis-free transfer characteristics, and hence, precisely determine the band gap. We produced ILG-based bilayer WSe2 FETs and demonstrated their ambipolar behavior. We estimated the band gap directly from the transfer characteristics, demonstrating the potential of ILG as a spectroscopy technique.

Field-controlled quantum anomalous Hall effect in electron-doped CrSiTe3 monolayer

“…Thanks to recent advancements in ionic liquid gating and chemical intercalations, such a doping concentration is now within reach of state-of-the-art experimental techniques. For example, ionic liquid gating can introduce up to 10 14 cm −2 order of carrier doping in a 2D system [51][52][53] . A recent experimental study reports 4 × 10 14 cm −2 of electron doping at the top two layers on the surface of CrGeTe 3 35 , exceeding our theoretical estimate of electron doping density (2.36 × 10 14 cm −2 ) necessary to achieve the quantized AHC in CrSiTe 3 .…”

Field-controlled quantum anomalous Hall effect in electron-doped CrSiTe$_{ 3 }$ monolayer: a first-principles prediction

“…For our calculation, oneelectron doping in the formula unit cell with 7.0Å lattice constant corresponds to carrier density as 2.36×10 14 cm −2 . Ionic liquid gating is representative method of charge doping where order of doping concentration is known as 10 14 cm −2 in 2D systems [46][47][48] . In recent study, about 2×10 14 cm −2 of electron doping for one layer is accomplished in CrGeTe 3 35 almost adjacent to our theoretical goal.…”

Field-controlled quantum anomalous Hall effect in electron-doped CrSiTe3 monolayer: a first-principles prediction

“…For our calculation, one-electron doping in the formula unit cell with 7.0Å lattice constant corresponds to carrier density as 2.36×10 14 cm −2 . Ionic liquid gating is representative method of charge doping where order of doping concentration is known as 10 14 cm −2 in 2D systems [46][47][48] . In recent study, about 2×10 14 cm −2 of electron doping for one layer is accomplished in CrGeTe 3 35 almost adjacent to our theoretical goal.…”