Regulation of electronic properties of ZnO/In2O3 heterospheres via atomic layer deposition for high performance NO2 detection

Abstract

Metal oxide semiconductor heterostructures are promising for gas sensors due to their unique chemical and electronic properties at the heterointerface. In this work, a highly sensitive and selective gas sensor for the detection of nitrogen dioxide (NO₂) is reported based on In₂O₃/ZnO heterogeneous nanospheres designed by atomic layer deposition (ALD). Their electronic properties at the In₂O₃/ZnO heterogeneous interface can be tuned by varying ZnO ALD cycles. Gas sensing tests show that ZnO ALD significantly improves the sensor performance of In₂O₃ nanospheres, rendering a response of 7.9 to 10 ppm NO₂ even at room temperature (RT). The sensor based on In₂O₃/ZnO with 30 cycles of ZnO ALD delivers the best response of 139.9 to 10 ppm NO₂ at an operating temperature of 180 °C, showing a nearly 6-fold enhancement over pristine In₂O₃. Meanwhile, the In₂O₃/ZnO sensor also exhibits a low limit of detection of 35 ppb, which allows for reliable detection of sub-ppm NO₂. The excellent sensor performances are correlated to the modulation of electron depletion layers at the In₂O₃/ZnO heterointerface, which sheds some light on designing new materials via ALD for the detection of hazardous gas molecules.