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5 November 2002 Highly luminescent Si quantum dots: new ways for size, position, and density control
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Phase separation and thermal crystallization of SiO/SiO2 superlattices result in ordered arranged silicon nanocrystals. The preparation method enables independent control of particle size as well as of particle density and spatial position by using a constant stoichiometry of the layers. Infrared absorption and photoluminescence spectra are measured as a function of annealing temperature to study the phase separation process. Three photoluminescence emission bands are observed. A band centered at 560 nm is found in as-prepared samples and vanishes for annealing above 700oC. A second band around 760 nm to 890 nm is detected for annealing temperatures above 500oC. The superlattices show a strong luminescence and a size dependent blue shift in the visible and near-infrared region after crystallization for temperatures above 900oC. The origin of the different photoluminescence bands at different phase separation stages of ultra thin SiOx layers are discussed based on transmission electron microscopy investigations and on correlations seen in photoluminescence spectra and infrared absorption. In addition, we report the PECVD preparation of amorphous SiO/SiO2 superlattices which show a similar size dependent luminescence after crystallization.
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Margit Zacharias, Johannes Heitmann, Lixin Yi, Rolf Scholz, Manfred Reiche, and Ulrich M. Goesele "Highly luminescent Si quantum dots: new ways for size, position, and density control", Proc. SPIE 4808, Optical Properties of Nanocrystals, (5 November 2002);

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