Berlin 2008 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 9: ZnO: Preparation and characterization I
HL 9.11: Vortrag
Montag, 25. Februar 2008, 17:45–18:00, EW 201
Properties of Li doped ZnO nanocrystals prepared from organometallic precursors — •Christian Rauch1, Markus R. Wagner1, Ronny Kirste1, Wolfgang Gelhoff1, Axel Hoffmann1, Michael Lehmann1, Matthias Driess1, Andrey Orlov2, and Sebastian Polarz2 — 1Technische Universität Berlin — 2Universität Konstanz
Applying a special organometallic precursor system, ZnO nanocrystals with considerable Li incorporation were produced. The structural, optical and electronic properties of the Li doped ZnO nanocrystals with lithium concentrations between 0.1 and 12 percent are studied by x-ray diffraction (XRD), photoluminescence (PL) and electron paramagnetic resonance (EPR) spectroscopy. The XRD patterns demonstrate that ZnO solely crystallises in the wurtzite structure, with no other phases present. The ZnO particles are of similar size (70-80nm) with no considerable strain. However, a deviation of the lattice parameters for Li containing ZnO samples could be observed. The incorporation of lithium in the lattice, the g-values and the charge transfer processes are studied by photo-excited EPR. The successful lithium incorporation on the Zn site leads to a reduction of the Fermi level compared to undoped ZnO. The PL spectra at helium temperature show a bound exciton transition in the range of I8, a luminescence band around 3.31eV with strong dependence on the Li concentration and a significant donor-acceptor-pair luminescence for medium lithium concentrations. The experimental data are discussed concerning the effectiveness of the shallow Li acceptor towards p-conductive ZnO nanocrystals.