One-Volt Oxide Thin-Film Transistors on Paper Substrates Gated by $\hbox {SiO}_{2}$ -Based Solid Electrolyte With Controllable Operation Modes

Microporous SiO₂ can provide large electric-double-layer (EDL) capacitance and negligible leakage current, owing to lack of electron carrier and limited mobility of mobile ions. The impedance spectroscopy (ionic-conductivity-frequency and capacitance-voltage characteristics) and Fourier-transformed infrared spectroscopy of microporous SiO₂ are characterized, which demonstrated that such dielectric is actually a solid-electrolyte dielectric. InGaZnO₄ thin-film transistors (TFTs) on paper substrates gated by microporous-SiO₂ solid electrolyte are fabricated at room temperature. The large EDL-specific capacitance (1.36 μF/ cm²) results in the paper TFTs operate at a battery-drivable low voltage of 1.0 V. Both depletion-mode (V_th = -0.45 V) and enhancement-mode (V_th = 0.25 V) operations are realized by rationally controlling the oxygen concentration in argon ambient during InGaZnO₄ channel deposition. Electrical characteristics with an equivalent field-effect mobility of ~ 21 cm²/V·s, a current on/off ratio of greater than 10⁵, and a subthreshold swing of ~ 80 mV/dec are demonstrated at low frequencies, which are promising for portable paper electronics.