Dresden 2009 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 9: Poster 1
HL 9.63: Poster
Monday, March 23, 2009, 14:30–17:00, P2
Electronic and Optical Properties of Lithium doped ZnO Nanocrystals — •Markus R. Wagner1, Ronny Kirste1, Christian Rauch1, Gordon Callsen1, Munise Cobet1, Wolfgang Gehlhoff1, Enno Malguth1,2, Michael Lehmann3, Sebastian Polarz4, Yilmaz Aksu5, and Matthias Driess5 — 1Institut für Festkörperphysik, TU Berlin — 2Georgia Institute of Technology, Atlanta — 3Optisches Institut, TU Berlin — 4Fachbereich Chemie, Universität Konstanz — 5Institut für Chemie, TU Berlin
Lithium doped ZnO nanoparticles were grown using a novel organo-metallic precursor system, where the resulting material is pre-organized on a molecular stage with Li concentration varied between 0.1% and 12%. XRD patterns and high resolution TEM images demonstrate that the ZnO crystals are of similar size (70-80nm) and solely crystallise in the wurtzite structure, with no other phases present. The successful incorporation of Li on the Zn lattice site is clearly proven by EPR measurements. It is shown that the Li doping leads to the introduction of lithium related acceptor states which consequently result in a strong lowering of the Fermi level. EPR and PL further show the additional introduction of Fe impurities. The lowering of the Fermi level is proven by the disappearance of the shallow donor EPR signal without optical excitation and by evident presence of Fe3+. The band-edge PL spectra are dominated by the bound exciton emission and a strong surface bound exciton line at 3.31eV. In addition, a DAP luminescence is observed and confirmed by time resolved PL. The binding energy of this acceptor state, introduced by Li doping, is calculated to 150meV.