Suspended GaN nanowires as NO2 sensor for high temperature applications

Abstract

We propose a gas sensor operable over a wide temperature range and using suspended GaN nanowires functionalized with Pt–Pd. The sensor is batch-fabricated by directly integrating the GaN nanowires onto batch-processed silicon microelectrodes in parallel. The high thermal stability of the sensor originates from a large band gap of GaN nanowires that enables the detection of NO₂ gas at an elevated temperature of up to 350 °C without a decrease in responsiveness. Exposed to NO₂ at 100–1000 ppm at 350 °C, the sensor shows a linear increment in relative response with respect to the change in gas concentration. The sensor results in a two- to four-fold increase in responsiveness to NO₂ at 100 ppm compared to NH₃ at 100 ppm and CO₂ at 1000 ppm. The nanowires suspended over a substrate provide increased surface area that could interact with gas molecules for enhanced responsiveness, and prevent any unnecessary interactions between the nanowires and the substrate.