Single-crystalline conic ZnO nanotubes were synthesized on Si(001) without catalysts by thermal chemical vapour deposition at 475 °C. The nanotubes grown along the ZnO  direction are sharp open-ended tips consisting of planar defects revealed by transmission electron microscopy and scanning electron microscopy. The nanotubes were formed by self-assembly of numerous six-radiated branches of hexagram nanosheets. The diameters and the wall thicknesses of the nanotubes are in the ranges 30-100 and 15-30 nm, respectively. The lengths and areal densities of the nanotubes are around 0.5 νm and 1-9 × 10 8 cm -2 , respectively. Field-emission measurements on the conic nanotubes show a low turn-on field of 3.5 V νm -1 at 10 νA cm -2 . The field-emission properties related to the nanotube density and geometry and the nonlinearity in the Fowler-Nordheim (FN) plot at lower field region are discussed.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Mechanics of Materials
- Mechanical Engineering
- Electrical and Electronic Engineering