Berlin 2008 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 3: Magnetic Semiconductors

MA 3.3: Vortrag

Montag, 25. Februar 2008, 10:45–11:00, H 1012

Magnetic and structural properties of nanocrystals embedded in semiconductors — •Shengqiang Zhou, Kay Potzger, Johannes v. Borany, Wolfgang Skorupa, Manfred Helm, Jörg Grenzer, and Jürgen Fassbender — Forschungszentrum Dresden-Rossendorf, Bautzner Landstrasse 128, 01328 Dresden

Traditional electronics can be greatly stimulated by an additional degree of freedom, i.e. the electron spin. In diluted magnetic semiconductors (DMS), transition metal (TM) ions are substituted onto cation sites of the host semiconductor. In case of magnetic coupling via the free charge carriers, spin polarized currents can be generated. However, most experimental investigations have only concentrated on reporting a high Curie temperature (T_C) and interpreted the observed ferromagnetism in terms of DMS without detail structural characterization. In this work, TM implant-doped ZnO, TiO₂ and Si samples are described by correlating magnetic and structural properties [1-2]. By means of synchrotron radiation x-ray diffraction, phase separations (Fe, Ni, Co and Mn-silicide nanocrystals) are observed. Those are the origin of the observed ferromagnetism. Depending on their crystalline structure, those nanocrystals are crystallographically oriented with respect to the host matrix. If they are randomly oriented, these nanocrystals are very difficult to detect by a simple Bragg-Brentano scan. This nature results in the pitfall of using XRD to exclude secondary phases in DMS materials.

[1] Shengqiang Zhou, et al., J. Appl. Phys. 100, 114304 (2006).

[2] Shengqiang Zhou, et al., J. Phys. D: Appl. Phys. 40, 964 (2007).