A Sputtered Silicon Oxide Electrolyte for High-Performance Thin-Film Transistors

Abstract

Abstract Low operating voltages have been long desired for thin-film transistors (TFTs). However, it is still challenging to realise 1-V operation by using conventional dielectrics due to their low gate capacitances and low breakdown voltages. Recently, electric double layers (EDLs) have been regarded as a promising candidate for low-power electronics due to their high capacitance. In this work, we present the first sputtered SiO 2 solid-state electrolyte. In order to demonstrate EDL behaviour, a sputtered 200 nm-thick SiO 2 electrolyte was incorporated into InGaZnO TFTs as the gate dielectric. The devices exhibited an operating voltage of 1 V, a threshold voltage of 0.06 V, a subthreshold swing of 83 mV dec −1 and an on/off ratio higher than 10 5 . The specific capacitance was 0.45 µF cm −2 at 20 Hz, which is around 26 times higher than the value obtained from thermally oxidised SiO 2 films with the same thickness. Analysis of the microstructure and mass density of the sputtered SiO 2 films under different deposition conditions indicates that such high capacitance might be attributed to mobile protons donated by atmospheric water. The InGaZnO TFTs with the optimised SiO 2 electrolyte also showed good air stability. This work provides a new pathway to the realisation of high-yield low-power electronics.