Low temperature NO2 sensing properties of RF-sputtered SnO-SnO2 heterojunction thin-film with p-type semiconducting behavior

In this work, a high-performance p-type semiconducting gas sensor was successfully fabricated based on a SnO-SnO2 p-n heterojunction thin-film formed via a radio-frequency (RF)-magnetron sputtering process. The structure, morphology, and chemical composition of the deposited thin-film were investigated using scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy, indicating that the thin-film had a microcrystalline structure and a mixed SnO and SnO2 phase. Compared to the previously reported p-type metal oxide semiconductor-based gas sensors, the gas sensor in this study exhibited competitive sensing performance for NO2 gas with a maximum response of 4.35-10 ppm NO2 at a low operating temperature of 60 degrees C, although it was fabricated via a simple RF- magnetron sputtering process. Moreover, the SnO-SnO2 p-n heterojunction thin-film gas sensor exhibited a high sensing selectivity to NO2 gas. The enhanced NO2-sensing performance of the fabricated gas sensor at low operating temperatures is possibly attributed to the formation of the SnO-SnO2 p-n junctions at the surface of the thin-film. The importance of this work is in the successful fabrication of the high-performance p-type semiconducting gas sensor using a simple and conventional RF-magnetron sputtering process.