Complementary dual channel gas sensor devices based on a role-allocated ZnO-graphene hybrid heterostructure.

Here, we present a new approach to dual channel gas sensors based on a role-allocated graphene-ZnO heterostructure, formed by the complementary hybridization of graphene and a ZnO thin film. The method enables cyclic and reproducible gas response as well as high gas sensitivity. The role allocation of graphene and ZnO was verified by studying the electrical transport properties of the heterostructure. The results indicated that the ZnO top-layer and graphene bottom-layer act as a gas adsorption layer and a carrier conducting layer, respectively. The charge interactions of the heterostructures were systematically explored by monitoring changes in transfer characteristics at room temperature and elevated temperature (T = 250 C) after introducing 20 ppm NO. These results can be understood in terms of the dual-channel effect of the graphene-ZnO heterostructures. Remarkably, an abrupt and reliable gas response under periodic NO gas injection was unambiguously achieved by the heterostructure-based gas sensors, and as ~30 times higher than those of a graphene-based gas sensor. These proposed heterostructures represent a fundamental building block of a complementary hybrid gas sensor with highly sensitive and reproducible gas response.