A La <sub>2</sub> O <sub>3</sub> Nanoparticle SO <sub>2</sub> Gas Sensor that Uses a ZnO Thin Film and Au Adsorption
Ting‐Jen Hsueh, Shih-Hsien Lee
Abstract
This study uses ultrasonic wave grinding technology to produce La 2 O 3 nanoparticles (La 2 O 3 -NPs). The TEM results show that the average diameter of these La 2 O 3 -NPs is approximately 20 nm. Au nanoparticles are adsorbed onto La 2 O 3 -NPs surfaces and integrated with a microelectromechanical systems (MEMS) structure to construct an Au/La 2 O 3 -NPs/ZnO/MEMS SO 2 gas sensor. The average diameter of the Au nanoparticles is about 5 nm. In a 300-ppb SO 2 gas ambience, the Au/La 2 O 3 -NPs/ZnO/MEMS gas sensor exhibits a greater sensor response than a ZnO/MEMS gas sensor or a La 2 O 3 -NPs/MEMS gas sensor. The experimental results show the ZnO thin film acts as a path for electron transport. As the concentration of the SO 2 gas increases, the sensor response increases. The sensor is also more sensitive to SO 2 gas than to CO 2 , CO or NO 2 gases if 300 ppb of SO 2 gas is introduced at the operating temperature of 260 °C.