Ultrasensitive ZnO-Nanorod-Structured Pressure Sensor by Integrating InSnZnO Thin-Film Transistor

Abstract

An ultrasensitive pressure sensor integrated thin-film transistor (TFT) was fabricated by using In-Sn–Zn-O (ITZO) thin film as an active channel layer and hydrothermally grown ZnO nanorods (ZnO NRs) as a sensing layer, in which polydimethylsiloxane (PDMS) film was used as a charge coupling layer between the ZnO NRs and the active channel. When an external mechanical pressure is applied to the ZnO NRs, piezo-induced charges generated within the ZnO NRs modulate the charge density in the channel of the ITZO TFT. This modulation effectively alters the drain-source current of the TFT, thereby enabling the sensor to detect and respond to the applied pressure. The integrated sensor exhibits a good response to external pressure, and the sensitivity can be significantly regulated by the gate-bias voltage, and the sensitivity in the subthreshold region is higher than that in the ON-state region with a regulation ratio of 157.6, the highest sensitivity of 0.57 kPa-1, and a response time of 33 ms. Meanwhile, the integrated pressure sensor can be employed to detect subtle external force stimulation, such as the generated output voltage of 250 mV under an external pressure of 35 mg. It is demonstrated that the integrated sensor has potential applications in milli-micro Newton-level force measurement and high-sensitive tactile perception.