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HL: Halbleiterphysik

HL 26: II-VI semiconductors II

HL 26.2: Vortrag

Dienstag, 28. März 2006, 15:30–15:45, POT 51

Defect mediated ferromagnetism in Zn_0.95Co_0.5O:(Cu,Al) thin films — •Lars Hartmann, Qingyu Xu, Heidemarie Schmidt, Holger Hochmuth, Michael Lorenz, Rüdiger Schmidt-Grund, Daniel Spemann, and Marius Grundmann — Universität Leipzig, Fakultät für Physik und Geowissenschaften, Institut für Experimentelle Physik II, Linnéstrasse 5, D-04103 Leipzig, Germany

Only recently it has been experimentally shown that defects mediate the ferromagnetism in Zn_0.95Co_0.05O codoped Cu [1]. Cu is an acceptor lying only 0.17 eV below the ZnO conduction band [2]. Our work focusses on the optimization of defect mediated ferromagnetism in n-conducting Zn_0.95Co_0.05O:(Cu,Al) thin films grown by pulsed laser deposition on sapphire substrates. Numerical simulations [3] revealed that for codoping with 10²⁰cm⁻³ Cu and 10²⁰cm⁻³Al even at room temperature the Cu acceptors are occupied by unpaired electrons. The influence of the Co transition metal on the position of the Fermi level has been accounted for by growing ZnO:(Cu,Al) reference samples. By relating the temperature dependent position of the Fermi level with the experimentally determined free charge carrier concentrations, it will be shown how unpaired electrons being localized on the Cu acceptors influence the magnetoresistance of Zn_0.95Co_0.05O:(Cu,Al) thin films.

[1] M.H.F. Sluiter, Phys. Rev. Lett. 94 (2005) 187204

[2] Y. Kani, Jpn. J. Appl. Phys. 30 (1991) 703

[3] using NextNano3 (http://www.nextnano.de/)