We report on photoluminescence (PL) experiments in CdS nanocrystals fabricated by sequential ion implantation in Al2O3 matrices. The PL spectrum and the spatial image of the PL intensity have been studied at 8 K using a scanning near-field optical microscope. The PL spectrum at each bright spot has been found to consist of narrow lines of various energies, although the spectrum measured by conventional optics shows a single and broad band locating below the free-exciton absorption energy. The origin of the sharp PL lines in CdS nanocrystals will be discussed.
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