Selective Oxidizing Gas Sensing and Dominant Sensing Mechanism of n-CaO-Decorated n-ZnO Nanorod Sensors

In this work, we investigated the NO2 and CO sensing, properties of n-CaO-decorated n-ZnO nanorods and the dominant sensing mechanism in n-n heterostructured one-dimensional (1D) nanostructured multinetworked chem-iresistive gas sensors utilizing the nanorods. The CaO-decorated n-ZnO nanorods showed stronger response to NO2 than most other ZnO-based nanostructures, including the, pristine ZnO nanorods. Many researchers have attributed the enhanced sensing, performance of heterostructured sensors to the modulation of the conduction channel-width or surface depletion layer width. However, the modulation of the conduction channel width is not the true cause of the enhanced sensing performance of n n heterostructured 1D gas sensors, because the radial modulation of the conduction channel width is not intensified in these-sensors. In this work, we demonstrate that the enhanced performance of the n-CaO-decorated n-ZnO nanorod sensor is mainly due to a combination of the enhanced modulation of the potential barrier height at the n n heterojunctions, the larger surface-area-to-volume ratio and the increased surface defect density of the decorated ZnO nanorods, not the enhanced modulation of the conduction channel width.