Comprehensive study of formaldehyde gas sensing performance of a GTO thin film incorporated with gold nanoparticles

There are lots of semiconducting metal oxides (SMOs) which have been used for detecting volatile organic compounds (VOCs), such as ZnO, SnO2, NiO, Ga2O3, WO3, ZnO, In2O3, etc. SnO2 is a widespread used SMO to develop a variety of chip to detect VOCs. In this work, a novel SMO gas sensor based on the combination of SnO2 material with a little proportion of wide bandgap (4.9 eV) Ga2O3 material, denoted as GTO, is proposed to detect formaldehyde (HCHO) gas. The studied sensor is synthesized by a radio-frequency (RF) sputtered GTO thin film and vacuum thermal evaporated gold (Au) nanoparticles (NPs) and treated with a post annealing. The related material properties are analyzed by X-ray Diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM), high-resolution scanning electron microscopy (HRSEM), and transmission electron microscopy (TEM). The decoration of Au NPs on the surface of GTO thin film causes a significant improvement on sensing performance. A high sensing response of 275 accompanied with a response (recovery) time of 16 s (11 s) under 20 ppm HCHO/air ambiance and an extremely low content of 50 ppb HCHO/air with a sensing response of 21 are obtained at 300 ℃. Furthermore, the studied sensor performs good selectivity, repetitivity, and long-term (120 days) stability.