Low-Cost pH Sensors Based on Low-Voltage Oxide-Based Electric-Double-Layer Thin Film Transistors

摘要

Indium-tin-oxide-based electric-double-layer (EDL) thin-film transistors (TFTs) are used as pH sensors. Such EDL devices show a low operation voltage of ${sim}{rm 1.5}~{rm V}$ and a high field-effect electron mobility $(mu_{{rm FE}})$ of ${sim}{rm 20}~{rm cm}^{{2}}cdot{rm V}^{-1}cdot{rm s}^{-1}$ when phosphorous-doped nanogranular ${rm SiO}_{{2}}$-based electrolyte films are used as the gate dielectric. The pH sensor based on such EDL TFT exhibits a high sensitivity of 58.1 ${rm m}{rm V}cdot{rm p}{rm H}^{{-1}}$ and a good linearity in the pH range from 2 to 12. In addition, such pH sensors present a low threshold voltage drift rate of 2.2 ${rm m}{rm V}cdot{rm h}^{{-1}}$ and a hysteresis voltage of 8.3 mV after a pH loop of $7to 4to 7to 10to7$.