Regulation of electronic properties of ZnO/In 2 O 3 heterospheres via atomic layer deposition for high performance NO 2 detection

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 (NO 2 ) is reported based on In 2 O 3 /ZnO heterogeneous nanospheres designed by atomic layer deposition (ALD). Their electronic properties at the In 2 O 3 /ZnO heterogeneous interface can be tuned by varying ZnO ALD cycles. Gas sensing tests show that ZnO ALD significantly improves the sensor performance of In 2 O 3 nanospheres, rendering a response of 7.9 to 10 ppm NO 2 even at room temperature (RT). The sensor based on In 2 O 3 /ZnO with 30 cycles of ZnO ALD delivers the best response of 139.9 to 10 ppm NO 2 at an operating temperature of 180 °C, showing a nearly 6-fold enhancement over pristine In 2 O 3 . Meanwhile, the In 2 O 3 /ZnO sensor also exhibits a low limit of detection of 35 ppb, which allows for reliable detection of sub-ppm NO 2 . The excellent sensor performances are correlated to the modulation of electron depletion layers at the In 2 O 3 /ZnO heterointerface, which sheds some light on designing new materials via ALD for the detection of hazardous gas molecules.