ZnO nanoneedles with tip surface perturbations: Excellent field emitters

ZnO nanoneedles were prepared on a silicon wafer through a chemical vapor deposition. The diameters of the needle tips were in a range of 20–50 nm. High-resolution transmission electron microscopy revealed that the nanoneedles were single crystals growing along the [001] direction and exhibiting multiple tip surface perturbations, just 1–3 nm in dimension. Field-emission measurements on the prepared nanostructures showed fairly low turn-on and threshold fields of 2.5 and 4.0 V/μm, respectively. The nanosize perturbations on the nanoneedle tips are assumed to cause such excellent field-emission performance.