Characterization, cathodoluminescence and field-emission properties of morphology-tunable CdS micro/nanostructures

High-quality, uniform CdS one-dimensional (1D) micro/nanostructures with different morphologies, e.g. microrods, sub-microwires and nanotips, are fabricated through a facile and effective thermal evaporation process. Their structural, cathodoluminescence and field-emission (FE) properties are systematically investigated. Microrods and nanotips exhibit sharp near band edge (NBE) emission and broad deep level (DL) emission, whereas sub-microwires show only the DL emission. A significant decrease in a DL/NBE intensity ratio is observed along a tapered nanotip towards a smaller diameter part. This behavior is understood under consideration of defect concentrations in the nanotips, as analyzed with high-resolution transmission electron microscopy (HRTEM). Field-emission (FE) measurements show that the nanotips possess best FE characteristics with a relatively low turn-on field of 5.28 V/¿m and the highest field-enhancement factor of 4819 among all 1D CdS nanostructures reported to date. The field-enhancement factor, turn-on and threshold fields are discussed related to structure morphology and vacuum gap variations under emission.