Abstract
The influence of copper as a metallic dopant on the properties of CdS colloidal quantum dots (CQDs) prepared by chemical co-precipitation method is investigated here. Dopant induced change in microstructural defects type, density, twinning angle, stress generation and some unusual emission behaviour are noticed. Besides, the substitution of Cu in mixed oxidation states i.e. Cu+ and Cu2+ with dominating nature of Cu+ is confirmed by x-ray photoelectron spectroscopy (XPS) studies. The crystallite sizes observed by transmission electron microscopy (TEM) are well supported by the sizes estimated using Scherer formula and are found to be either below or comparable to Bohr excitation radius of bulk CdS. A competitive intensity variation between band edge emission and intrinsic defect assisted emission without generation/contribution of extrinsic defect sponsored emission is observed. The microstructural defects (nanotwinning angle) and related stress may be the possible sources of variation in crystallite size, crystallinity and uncommon recombination process in the CQDs.
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