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.