Zinc oxide is a direct wide band gap semiconductor. The introduction of magnetic elements can produce semiconductors which are ferromagnetic close to room temperature [1]. Potential applications of such materials are e.g. magnetic sensors and actuators, high-density memory. The properties of ZnO can be tuned chemically and by size variation. However, the efficient doping of nanocrystals is difficult [2] and the location of the dopant atoms is important for their function. Atoms on substitutional sites in the wurtzite structure of ZnO behave differently compared to dopants on interstitial sites or on particle surfaces.

Doped Nanocrystalline zinc oxide powders are produced by evaporation of mixed precursors in a laser flash evaporator and subsequent particle generation by chemical vapor synthesis (CVS) [3, 4]. The powders are characterized by means of X-ray diffraction, nitrogen absorption, and transmission electron microscopy. XAFS spectra at the Zn- and Cr-K X-ray absorption edges supply information on the local structure of the nanocrystalline zinc oxide materials. The XAFS spectra are analyzed by Reverse Monte Carlo Methods (RMC) [4, 5]. A careful analysis of the partial pair distribution functions for the different cations provided by RMC reveals the location of the dopant atoms within the host structure.


References

[1] Pearton, S. J., Abernathy, C. R., Overberg, M. E., Thaler, G. T., Norton, D. P., Theodoropoulou, N., Hebard, A. F., Park, Y. D., Ren, F., Kim, J., Boatner, L. A., Appl. Phys. Lett., 93 (2003), 1
[2] Shim, M. , Wang, C., Norris, D. J., and Guyot-Sionnest, P., , MRS Bulletin 12/2001, 1005
[3] Brehm, J., Winterer, M., and Hahn, H., Proceedings of PARTEC 2004, 1.4
[4] Winterer, M., Nanocrystalline Ceramics - Synthesis and Characterization, Springer 2002
[5] Winterer, M., J. Appl. Phys. 88 (2000), 5635

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1. Characterization of Nanomaterials by Scattering and Spectroscopy