Tuning the on/off current ratio in ionic-liquid gated multi-layer MoS₂ field-effect transistors

Ionic-liquid gated multi-layer MoS₂ field-effect transistors were fabricated and their electrical properties related to maximum depletion depth, bulk neutral and surface accumulation conduction were investigated in detail. A negative back-gate bias resulted in a depletion of the bulk neutral channel at the bottom interface, which significantly enhanced transistor performance in terms of the on-current to off-current (I_on/I_off) ratio and the off-state current level. The experimental results were verified by numerical simulations and analytical equations. These findings are critical for the optimization of the I_on/I_off ratio of multi-layer MoS₂ transistors for energy efficient electronics and low power applications.