Enhanced field emission from the ZnO nanowires by hydrogen gas exposure

ZnO nanowires (ZNWs) were synthesized on Co-coated Si wafer via a carbon thermal reduction vapor transport method. Scanning electron microscopy, X-ray diffraction and transmission electron microscopy investigations show that these ZNWs present a high-quality single-crystalline hexagonal structure. Field emission (FE) characteristics of the ZNWs film were measured. A low turn-on voltage for driving a current density of 0.1 μA/cm2 is about 3.9 V/μm. The field enhancement factor was determined to be ∼ 1180 for ZNWs film. Exposure of H2 during FE causes a permanent increase in the FE current and a decrease in the turn-on field. Also, the field enhancement factor γ was finally increased from 1180 ± 20 to 1510 ± 20 after FE saturation.