Structural, Photoluminescence, and Field Emission Properties of Vertically Well-Aligned ZnO Nanorod Arrays

The self-assembled growth of vertically well-aligned ZnO nanorod arrays with uniform length and diameter on Si substrate has been demonstrated via thermal evaporation and vapor-phase transport. The structural, photoluminescence (PL), and field emission properties of the as-prepared nanorod arrays were investigated. The PL spectrum at 10 K shows a strong and sharp near-band gap emission (NBE) peak (full width at half-maximum (FWHM) = 4.7 meV) and a weak neglectable deep-level emission (DL) peak ( I NBE / I DL = 220), which implies its good crystallinity and high optical quality. The room-temperature NBE peak was deduced to the composition of free exciton and its first-order replicas emissions by temperature-dependent PL spectra. The field emission measurements indicate that, with a vacuum gap of 400 μm, the turn-on field and threshold field is as low as 2.3 and 4.2 V/μm. The field enhancement factor β and vacuum gap d follows a universal equation.