Low pressure hydrogen sensing mechanism based on the field emission of defect-controlled ZnO nanorods

Abstract

ZnO nanostructures are widely used for the atmospheric pressure hydrogen detection based on the variations of the resistances. However, the low pressure gas sensing from the ZnO is still immature due to weak resistance effect. Here we report the low pressure hydrogen sensing method based on the field emission of defect-controlled ZnO nanorods in wide pressure range of 10-3 to 10-7 Pa. The investigation reveals that while hydrogen atom adsorbing on the site of the oxygen defect, the field emission of ZnO could increase from the reduction of the effective work function (WF) of ZnO, leading to the hydrogen sensing performance. Otherwise, the effective WF of ZnO will increase, with hydrogen adsorption on the site of the zinc defect. In addition, the sensing performance could be enhanced with increasing contents of oxygen defects.This study not only gives the insight into the low pressure hydrogen sensing mechanism from the field emission of ZnO, but also expands the understanding of the electronic properties of the ZnO nanomaterial with various defects and annealing conditions.