Enhanced Electron Filed Emission from Single-Crystalline ZnO Nanoneedles

In this paper, we report the synthesis of ZnO nanoneedles by a facile hydrothermal route at mild reaction temperature without the addition of any surfactant. The X-ray powder diffraction (XRD), Raman spectra, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were sued to characterize the morphologies, crystal phase, microstructures and components of the samples. Our results show that the as-obtained ZnO nanoneedles with sharp tips are well crystallines elongated preferentially in the [0002] direction. Photoluminescence (PL) of as-grown ZnO nanoneedles show two emission peaks centered at around 420 and 487 nm, respectively, both of which originate from the singly ionized oxygen vacancies. Field electron emission studies show that the as-prepared products have good FE performance characterized by lower turn-on field of 4.75 V/mu m and high field-enhancement factor 2976 and good stability.