Synthesis and magnetic characterization of co-axial Ge1-xMnx/a-Si heterostructures

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Barth, Sven
Kazakova, Olga
Estrade, Sonia
Hobbes, Richard G.
Piero, Francesca
Morris, Michael A.
Holmes, Justin D.
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American Chemical Society (ACS)
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A method for synthesizing Ge1–xMnx/a-Si core–shell nanowires (x = 0.3(1)–1.0(2)) using a supercritical fluid deposition technique, with a homogeneous distribution of manganese along the entire lengths of the crystalline Ge cores but not in the a-Si shells, is reported. Investigations into the magnetic properties of the heterostructured nanowires revealed a significant influence of the amorphous Si shell covering the surface of the core Ge0.997Mn0.003 nanowires compared to pristine Ge0.997Mn0.003 nanowires with no a-Si coating. The magnetic data revealed diminished values of both the remanence and the saturation magnetization for pristine Mn-doped Ge nanowires at higher temperatures when compared to the Ge1–xMnx/a-Si core–shell nanowires, whereas both parameters increased as the temperature dropped down to 5 K. Differences in the temperature-dependent evolution of the coercivity were observed in the magnetically harder core–shell nanowires compared to the pristine Ge0.997Mn0.003 nanowires, showing a drop of 26% at 5 K vs room temperature compared to a drop of 66% for the pristine nanowires. The low dopant concentration (0.3(1)%) of Mn in the core–shell nanowires, combined with the observed ferromagnetic properties, suggests a combination of hole-mediated exchange and confinement processes are responsible for the observed properties. Our observations show the importance of a protective layer in covering the oxidation-sensitive dilute magnetic semiconductor nanowires.
Germanium , Nanowire , Heterostructure , Core-shell , Magnetic properties , Structural characterization
Barth, S., Kazakova, O., Estrade, S., Hobbs, R. G., Peiro, F., Morris, M. A. and Holmes, J. D. (2011) 'Synthesis and Magnetic Characterization of Coaxial Ge1–xMnx/a-Si Heterostructures', Crystal Growth & Design, 11(12), pp. 5253-5259.
© 2011 American Chemical Society. This document is the Accepted Manuscript version of a Published Work that appeared in final form in Crystal Growth & Design copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see