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MSE Seminar Series: Petra Reinke and Jerrold Floro
Friday, October 10, 2014
1:00 p.m.
Room 2108, Chemical and Nuclear Engineering Bldg.
For More Information:
JoAnne Kagle
301 405 5240

Magnetic Doping of Ge-Quantum Dots with Mn:  Complex Interactions On and Below the Surface
Petra Reinke
, Associate Professor; and
Jerrold Floro, Associate Professor
Department of Materials Science and Engineering
University of Virginia

The magnetic doping of Ge-QDs is highly coveted and has been pursued for several years. The Ge-Mn-Si substrate system presents a complex challenge, and the competition between functional dopant integration and the formation of intermetallic compound phases makes the magnetic doping a considerable, and maybe insurmountable, challenge. We will first discuss the interaction of Mn with all the relevant growth surfaces: Si(001), the Ge(001) wetting layer, and the Ge{105} QD facet, as well as the co-deposition of Mn and Ge. Monoatomic Mn-wires form on Si(001), and their magnetic signatures allow unique insight into the relation between bonding and magnetism. At higher growth temperatures required for QD self-assembly, Mn is highly mobile both on and below the growth surface.  As a consequence, Mn follows a complex evolutionary pathway, forming metastable diamond cubic solutions with the Ge dots and hidden in the Si substrate underneath the dots. With additional Mn, however, silicides form “cooperatively” from the QDs, exclusive of any germanide phases. These rapidly tie up all the available Mn.  We discuss the challenges of measuring ferromagnetism when only a sub-monolayer of Mn is present, even using SQUID magnetometry.  Funding from NSF-DMR is gratefully acknowledged.

About the Speakers

Petra Reinke received her diploma in Chemistry from the University of Konstanz, and then moved for a PhD in physics to the Max-Planck Institute for Plasmaphysics in Garching. After a postdoctoral year at the Ecole Polytechnique in Montreal she moved to the University of Basel in Switzerland to finish her Habilitation (Assistant professor). She started her surface science research in carbon materials and interfaces at this time, and subsequently moved to the University in Virginia where she works on Surface and Nanoscience in a wide range of materials.

Jerry Floro is an Associate Professor of Materials Science at UVa.  He received his B.S. in Physics from Colorado State University and his Ph.D in MSE from MIT.  In between he spent 3 years as a thin film engineer at the IBM Watson Research Center.  He joined Sandia National Labs in 1992, and then switched to academia in 2006 upon moving to Charlottesville.  His research emphasizes self-assembly at the nanoscale in both thin films and bulk thermo-mechanically processed materials for nanoelectronics, thermoelectrics and magnetism.

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