Giant Enhancement of Field Emission from Selectively Edge Grown ZnO–Carbon Nanotube Heterostructure Arrays via Diminishing the Screen Effect

Abstract

Novel selectively edge grown ZnO–carbon nanotube (CNT) heterostructure field emission (FE) arrays have been fabricated by a facile and repeatable two-step process. First, with the combined effect from a ZnO seed layer and a passivation layer for nanorod growth, ZnO nanorods could only grow on the edge of a 4 μm diameter circle. Meanwhile, the local morphology such as ZnO nanorod density, uniformity, and growth direction can be modulated by the thickness of ZnO seed layer. With this adjustment, the FE performance of the ZnO nanorod ring pattern arrays is significantly improved. Then CNTs were radically grown on the surface of the ZnO nanorod ring pattern arrays. As a consequence of all these optimizations, the lowest turn-on field of 2.1 V/μm, threshold field of 3.19 V/μm, and a current density of 7 mA/cm2 at a field of 4.95 V/μm were ultimately obtained. Via calculating the electrostatic field distribution, it was found that this giant enhancement of FE performance is due to the typical morphology which c...