SnOX based μW-power dual-gate ion-sensitive thin-film transistors with linear dependence of pH values on drain current

Dual-gate (DG) Ion-sensitive thin-film transistor (ISTFT) pH sensors based on tin oxide (SnOx) channel and Al2O3 sensor membrane have been developed. DG SnOx thin film transistors with Al2O3 dielectrics were fabricated, illustrating effective linear current modulation under top gate bias. The SnOX DG-ISTFTs with 10-nm Al2O3 sensor membrane can operate at a low single supply voltage of -1.0 V with a low power consumption around 3 μW. In contrast to most reported ISTFT pH sensors, which show linear dependence of pH value on threshold voltage, and are not directly readable, the SnOx DG-ISTFTs exhibit linear pH dependence on directly readable drain current. We demonstrate a high sensitivity of 83.87 nA/pH and a low current hysteresis of 1.65 nA after a pH loop of 7-10-7-4-7. This enables significantly simplified readout circuits with reduced power consumption. The SnOx based DG-ISTFTs may have huge practical potential as portable and wearable biosensors and chemical sensors.