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

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.