Berlin 2005 – scientific programme

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HL: Halbleiterphysik

HL 23: II-VI Halbleiter II

HL 23.8: Talk

Saturday, March 5, 2005, 12:30–12:45, TU P-N202

Synthesis and Characterization of Co-doped ZnO Nanocrystals — •Niklas Volbers, Daniel Pfisterer, Joachim Sann, Bruno Meyer und Detlev Hofmann — I. Physikalisches Institut, Justus-Liebig-Universität-Giessen, Heinrich-Buff-Ring 16, D-35392 Giessen, Germany

Transition-metal doped ZnO is a promising candidate for transparent ferromagnetic semiconductors and its technical application will demand nanoscale structures. We have prepared Co-doped ZnO nanoparticles using a wet-chemical synthesis route. Recently, it was shown that nanocrystals prepared in a similar way show roomtemperature ferromagnetism [1]. We have studied the growth mechanism of the doped nanoparticles and the incorporation of Co into the nanocrystals. Compared to undoped nanocrystals the doping results in a reduced growth rate and reduced size of the nancrystals. The incorrporation of the Co dopant in the form of Co²⁺ substituting Zn is confirmed by the observation of the internal crystal field transitions in absorption and emission spectroscopy. It is in line with electron paramagnetic resonance experiments. However, no evidence for ferromagnetism is found so far. This is probably related to the small size of our nanocrystals (∼3nm), while ferromagnetism was observed for much bigger nanocrystals (>100 nm) [1].

[1] Schwartz et al.: Magnetic Quantum Dots: Synthesis, Spectroscopy, and Magnetism of Co²⁺- and Ni²⁺-Doped ZnO Nanocrystals. J. Am. Chem. Soc., 125: 13205-13218, June 2003.