Event
MSE Seminar - Professor Jerry Floro, University of Virginia
Friday, October 2, 2009
1:00 p.m.
Room 2108, Chemical and Nuclear Engineering Bldg.
Annette Mateus
301 405 5207
amateus@umd.edu
"Ge/Si: Quantum Dots, Films and Magnetism"
GexSi1-x readily grows heteroepitaxially on Si (001), with a compressive lattice misfit strain up to 4% for the case of pure Ge on Si. GeSi has arguably been *the* model materials system for investigating the energetics and kinetics of misfit dislocation introduction, and similarly for studies on the strain-driven self assembly of coherent islands, aka quantum dots. In the first part of my talk I?ll discuss our understanding of the growth science of quantum dots, especially the role of elastic repulsion between dots that accelerates coarsening, ordering, and shape transitions. But this is older work, and I will quickly try to move into newer, albeit early stage, research on making Ge magnetic through the introduction of Mn as a spin dopant. This is challenging since the solid solubility of Mn in Ge is ridiculously low, forcing us to work far from equilibrium in order to form metastable solutions up to several atomic percent. We are deliberately growing amorphous Ge films, where the goal is to better understand the origins of magnetism and to demonstrate electric-field-controlled ferromagnetism. But ultimately the interest is in making Ge:Mn epitaxial quantum dots, a far more challenging prospect, since dot self-assembly requires high adatom mobility, which is in turn antithetical to metastable incorporation of Mn. I?ll discuss strategies for accomplishing this, and show some very preliminary results. The long-term goal is a new logic switch based on interactions between gated magnetic dots.
