Oxide-Based Electric-Double-Layer Thin-Film Transistors on a Flexible Substrate

Flexible electric-double-layer (EDL) InGaZnO thin-film transistors (TFTs) were fabricated on a plastic substrate at room temperature. A large EDL gate capacitance, 0.22 $\mu \text{F}$ /cm 2 , at 20 Hz was achieved using 200-nm-thick radio frequency magnetron sputtered porous SiO 2 as the dielectric layer, which is equivalent to ~15.7-nm thermally grown SiO 2 . The devices, therefore, show a low operating voltage of 1 V, a high current ON–OFF $\textsf {ratio}>\textsf {10}^{\textsf {5}}$ , and a low subthreshold swing < 0.12 V/decade. These properties were maintained even after bending, suggesting that the TFTs are suitable for applications in portable sensors and rollable displays.