Silicon Nanostructure based Surface Acoustic Wave Gas Sensor

Abstract

Surface acoustic wave (SAW) gas sensors with a nanostructured material-based sensing layer are highly desirable in microelectromechanical systems (MEMS) gas sensors to achieve improved sensitivity, time response, and recovery time. Herein, a novel SAW gas sensor with a nanostructured silicon (Si)-based sensing layer was developed. Finite element analysis was employed to determine the dimensions of the sensing material. Moreover, a SAW sensor with a four-pair input/output aluminium interdigital transducer (IDT) was fabricated and tested with carbon dioxide gas (CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> ), with a concentration in the range of 500–2000 ppm. The results reveal that an Si nanostructure produces better sensitivity, and faster response and recovery time, compared to a layered Si-based SAW sensor. At 2000 ppm, a frequency shift of 4.62 kHz was recorded, while the time response and recovery time of 31 s and 40.5 s was reported, respectively. The proposed Si nanostructure as the sensing layer for the SAW gas sensor demonstrated significant performance with higher sensitivity than previously reported devices, and has the potential to act as a next generation MEMS SAW gas sensor.