Characterization, Cathodoluminescence, and Field-Emission Properties of Morphology-Tunable CdS Micro/Nanostructures

Abstract

High-quality, uniform one-dimensional CdS micro/nanostructures with different morphologies-microrods, sub-microwires and nanotips-are fabricated through an easy and effective thermal evaporation process. Their structural, cathodoluminescence and field-emission properties are systematically investigated. Microrods and nanotips exhibit sharp near-bandedge emission and broad deep-level emission, whereas sub-microwires show only the deep-level emission. A significant decrease in a deep-level/nearband-edge intensity ratio is observed along a tapered nanotip towards a smaller diameter part. This behavior is understood by consideration of defect concentrations in the nanotips, as analyzed with high-resolution transmission electron microscopy. Field-emission measurements show that the nanotips possess the best field-emission characteristics among all 1D CdS nanostructures reported to date, with a relatively low turn-on field of 5.28 V mm 1 and the highest field-enhancement factor of 4 819. The fieldenhancement factor, turn-on and threshold fields are discussed related to structure morphology and vacuum gap variations under emission.