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MA: Magnetismus

MA 7: Micro- and Nanostructured Magnetic Materials I

MA 7.2: Vortrag

Montag, 27. März 2006, 15:15–15:30, HSZ 03

Electronic structure of Co in ZnO Thin Films — •Huijan Zhou¹, Christoph Knies¹, Detlev M. Hofmann¹, Niklas Volbers¹, Jan Stehr¹, Swen Graubner¹, Bruno K. Meyer¹, Peter J. Klar², and Wolfram Heimbrodt² — ¹I. Physics Institute, Justus-Liebig-University Giessen, Heinrich-Buff-Ring 16, D-35392 Giessen, Germany — ²Material Research Center and department of semiconductor physics, Renthof 5, LB2, D-35032 Marburg/Lahn, Germany

The concern of this work is to investigate cobalt doped ZnO thin films prepared via sol-gel methods. X-ray diffraction (XRD) and Raman spectroscopy are applied to monitor the crystal quality and the segregation phase of the film. Within the concerned doping concentration (0.5%-10%) XRD shows mainly the diffraction peaks from wurtzite ZnO (0002) and (0004) planes without secondary phases. No Co-related phonon modes are observed, as proved by Raman measurements in comparison with those of a pure CoO thin films. The ZnO:Co films have a typical grain size of 20-50 nm with a thickness of 300-500 nm. Fine structures of Co²⁺ (3d7) internal d-d absorption are well resolved. All zero phonon lines (ZPL) and phonon replica related to ⁴T₁(F) → ⁴A₂ are observed, which demonstrates high crystal quality and the incorporation of Co²⁺ on Zn²⁺ lattice sites in a tetrahedral symmetry with a trigonal distortion. In the visible region transitions due to ⁴A₂ → ²T₁(G), ⁴T₁(P), ²A₁(G) processes are observed. Magnetic properties of ZnO:Co have been characterized. Electron paramagnetic resonance measurements are in agreement with the simulation of Co-doped ZnO powder. So far no evidence for ferromagnetism is obtained.