The n-ZnO/n-In₂O₃ heterojunction formed by a surface-modification and their potential barrier-control in methanal gas sensing

ZnO-modified In₂O₃ heterojunction with superior methanal (HCHO) sensing was synthesized by a simple and cost-efficient two-stage route, and the ZnO was promoted to uniformly attach on the surface of In₂O₃ nanostructure by using sonochemical synthesis. The In₂O₃ nanostructure modified with ZnO could remarkably enhance the gas response to HCHO and lower the detection limit respectively. Those were attributed to the fact that the electron transfer was modulated by the heterojunction in the interface between the ZnO and In₂O₃ nanostructure. The coalesced layer of the ZnO on the surface of In₂O₃ nanostructure facilitated to the formation of a heterojunction between the ZnO and In₂O₃ interface, which acted as a lever of electron transfer to increase the changes of resistance. Thus, a simple and cost-efficient method was reported here to modulate electron transfer and increase the variation amplitude of resistance in gas-sensing. The gas response of ZnO-modified In₂O₃ nanostructure was upgrade to more 6 times than intrinsic In₂O₃ for 100 ppm HCHO vapor at 300°C. The results were valuable for great In₂O₃ nanostructure gas sensor applied to detecting toxic gas.