Fabrication and properties of non-balance electric bridge gas sensor based on a single Sb doped ZnO microwire

Abstract

Zinc oxide (ZnO) is a wide direct band gap (3.37 eV) II-VI semiconductor material with a wide range of applications in light emitting devices, solar cells, field emission devices, gas sensors, etc. Over the past decades, metal oxide semiconductors have been investigated extensively for sensing various types of vapors and toxic gases. Among the various metal oxides for gas sensing applications, ZnO is one of the potential materials for high response, stability and sensitivity to volatile organic gases. At present, the ZnO-based gas sensor has a relatively high operating temperature. However, the stability and lifetime of gas sensors operating under high temperature conditions with a long term will be greatly reduced. In addition, the power consumption of gas sensors is also significantly increased. Furthermore, there can exist the potential of explosion when gas sensors are used to detect the flammable gases at high temperature. Therefore, it is necessary to improve the sensing properties and reduce the operating temperature of gas sensors. In this paper, ultra-long, large-sized Sb doped ZnO microwires are successfully prepared by using chemical vapor deposition. The gas sensor is based on the principle of non-balance electric bridge, and a single Sb doped ZnO microwire is used as a bridge arm <i>R</i>₄ of non-balance electric bridge to produce a gas sensor that can work at room temperature. The results show that the response-recovery curves of sensors at the acetone and ethanol concentrations of 20 ppm, 50 ppm, 100 ppm and 200 ppm (1 ppm = 10^–6) are rectangular at room temperature, and have stable current values in air and measured gas, and the response value of the device gradually increases with gas concentration increasing. Furthermore, the detection of acetone and ethanol gas reveal that the device has better selectivity for acetone gas. The response of the gas sensor to 200 ppm acetone is about 243%, with response and recovery time of 0.2 s and 0.3 s, respectively. Compared with the traditional resistive gas sensor, this non-balanced electric bridge sensor has high response, fast response and recovery time. In addition, the sensing mechanism of the device is also studied.