The quantum confined Stark effect is observed for quantum dots (QD's) exposed to randomly fluctuating electric fields in epitaxial structures. These fields, attributed to charges localized at defects in the vicinity of the QD's, lead to a jitter in the emission energies of individual QD's. This jitter has typical frequencies of below about 1 Hz and is characteristic for each QD thus providing a unique means to unambiguously identify the emission spectra of single QD's. Up to eight lines are identified for individual QD's and attributed to excitonic, biexcitonic, and LO-phonon-assisted transitions. The intensity of the LO-phonon replica is surprisingly large corresponding to Huang-Rhys factors of about one

Monocrystalline ZnO columns grown in electrodeposition were converted to ZnS using ion exchange reactions in H2S or S vapor. At ∼400 °C the reaction with H2S only affects a thin layer of 10–30 nm thickness at the surface of the ZnO crystallites, and ZnS-coated ZnO columns are produced. Exploiting the large difference in etch resistance between ZnS and ZnO, the ZnO core of the columns can be removed, and a tubular structure of ZnS can be prepared. Typical dimensions of the ZnS tubes are a length of 1–3 μm, a diameter of 100–300 nm, and a wall thickness of 10–30 nm. The ZnS tubes have the same distribution, alignment, and surface morphology as the original ZnO columns. The reaction in S vapor is suitable to produce solid ZnS columns.

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