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Keywords:

  • cadmium sulfide;
  • cathodoluminescence;
  • field emission;
  • microstructures;
  • nanostructures;
  • semiconductors

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-band-edge emission and broad deep-level emission, whereas sub-microwires show only the deep-level emission. A significant decrease in a deep-level/near-band-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 µm−1 and the highest field-enhancement factor of 4 819. The field-enhancement factor, turn-on and threshold fields are discussed related to structure morphology and vacuum gap variations under emission.