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 ED' gate capacitance, 0.22 μF/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 ratio > 10
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.