Field Emission Properties Of Zno Single Crystal Microtubes

Field emission properties of ZnO single-crystal microtubes were investigated in this work. The turn-on voltages for the as-grown and postannealed ZnO microtube samples were 5.6 and 6.4 V/mu m, respectively. The emission current density was 11 mA/cm(2) at an applied field of 20 V/mu m for the as grown ZnO microtube and 12.5 mA/cm(2) at an applied field of 13 V/mu m for the postannealed ZnO microtube. Due to the relatively large tip area (in comparison with ZnO nanomaterials) of the ZnO microtubes, the intrinsic field emission enhancement factor beta of the ZnO microtube was comparatively low (estimated to be around 6.5). However, the experimental beta values were quite high (418 for the as-grown ZnO microtube and 1466 for the postannealed ZnO microtube), indicating strong field emission characteristics of the ZnO microtubes.