The Growth of One-Dimensional Single-Crystalline AlN Nanostructures by HVPE and Their Field Emission Properties

Single-crystalline AlN nanostructures, such as thin films, nanoneedles, nanocolumns, and nanowires, depending on the controlled gas-flow ratio, are synthesized by halide vapor-phase epitaxy (HVPE). In comparison with a typical vapor/liquid/solid (VLS) mechanism for the growth of nanowires, well-aligned AlN nanorod arrays with diameters below 20 mm are grown on a catalyst-free Si substrate though a vapor/solid (VS) mechanism. Their structural and optical properties are measured by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL). In particular, AlN nanorods exhibit an excellent field emission property with a low turn-on field of 2.25 V mu m(-1). The field enhancement factor is estimated to be about 784 due to well-aligned, needle-shaped, AlN nanorods.