Broad-Range Modulation of Guest-Species Interactions in MoS₂ Transistors for Electrochemical Phase Transitions

In the realm of two-dimensional (2D) transition metal dichalcogenides (TMDs), the utilization of ionic gating has emerged as a powerful means, advancing electrostatic and electrochemical manipulations in a wide range of electronic properties. In general, the conventional ionic gating approach is, however, performed within the conservative low-voltage regime, which cannot take advantage of its full range of gating power as well as electrochemical interactions. Herein, we present an all-inclusive ionic gating technique covering from electric-double-layer gating (low-voltage stage) to insulator-to-metal transition (high-voltage stage). In the latter, the structural/electronic phase transformation of MoS₂ is triggered by intercalation of guest ions, 1-Ethyl-3-methylimidazolium ([EMIM]+), which is one of the most conventional cation used in ionic gating devices and the greater details in its characteristics are studied as a versatile and fast-switching device. In such device operated under high-bias condition, it is critical to prevent undesirable chemical reactions, and so we introduce a very thin high-k dielectric passivation layer deposited through atomic layer deposition, strategically protecting the electrodes and also reducing leakage current (so, I_on/off > 10⁶ ) while operating in liquid-based electrolytes at room temperature. In addition, to effectively accumulate the charge in the channel and control the voltage range in which phase transiton can occur, a dual gating method was introduced just adding simple process fabricating bottom gate using high-k dielectric and a way to effectively operate the device was explored. This work underscores the potential for phase-change-based devices and hybrid gating schemes as promising avenues for advancing the field of 2D materials and nanoelectronics, offering unprecedented control and functionality in future electronic systems.