Ion-gated tungsten oxide based electrochemical transistors with subthreshold slopes approaching the thermodynamic limit

Electrochemical transistors (ECTs) are switches that are controlled by ionic gating, and find emerging applications in electronic devices and chemical sensors. In this paper, we fabricate microscale tungsten oxide (WO x ) ECTs and study their subthreshold characteristics. We optimize the film deposition process to produce WO x films with various oxygen concentrations, and investigate their physical and chemical properties. We employ transparent amorphous WO 3 films as the channel material for ECTs, and experimentally investigate their subthreshold behaviors by injecting different metal ions in electrolytes. In addition, we explore the dynamic response of the WO 3 ECT. Gated by cation intercalation, we find that these WO 3 ECTs can obtain a subthreshold slope as low as 60 mV/dec at room temperature, approaching the same thermodynamic limit as field-effect transistors. The material and device strategies provide a route to realizing future computing and sensing devices.