AVS 45th International Symposium
    Nanometer-scale Science and Technology Division Tuesday Sessions
       Session NS-TuA

Paper NS-TuA10
Surface Oxidation of Germanium Quantum Dots Produced by a Laser Vaporization-Controlled Condensation Technique

Tuesday, November 3, 1998, 5:00 pm, Room 321/322/323

Session: Quantum Wires and Quantum Dots
Presenter: S. Li, Virginia Commonwealth University
Authors: S. Li, Virginia Commonwealth University
S. Wen, Virginia Commonwealth University
M. Wiess, Virginia Commonwealth University
J.A. Carlisle, Virginia Commonwealth University
M.S. El-Shall, Virginia Commonwealth University
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Weblike aggregates of coalesced Ge quantum dots are produced by a laser vaporization-controlled condensation technique. The surface oxidation of Ge quantum dots is studied with Fourier-Transform Infrared Spectroscopy (FTIR), core-level X-ray photoelectron spectroscopy (XPS), and x-ray diffraction (XRD). The freshly prepared Ge particles possess the bulk Ge crystal lattice. After the particles are removed from the reaction chamber for 10 min, the surface of the particles becomes oxidized as seen by XPS and FTIR. However, the FTIR peaks are very weak. Further oxidation of the Ge core, by exposure of the Ge quantum dots to air, results in the epitaxial growth of surface oxidation layers, as confirmed from XRD and XPS. After the particles are stored in air for two months, sharp features corresponding to crystalline GeO@sub 2@ are observed in the XRD spectrum. The surface-oxidized Ge quantum dots do not show photoluminescence from the core Ge particles, but rather show the emission characteristics of GeO@sub 2@, with photoluminescence lifetimes less than 20 ns. The photoluminescence is thus attributed to defect states in GeO@sub 2@.