The Center for Emergent Materials Winter Colloquium will be Wednesday, March 3, 2010 from 4-5pm in the Smith Seminar Room, Physics Research Building.
Prof. Ian Appelbaum, University of Maryland. presents “Lateral Spin Transport and Electrostatic Gating in Silicon.”
Abstract:
Silicon, the materials basis for most semiconductor electronics devices, has been known for decades to have an extraordinarily long spin lifetime. Using unique spin-polarized hot-electron injection and detection techniques, we have observed unprecedented spin coherence, and extracted very long spin lifetimes of conduction electrons traveling over macroscopic distances, even in the millimeter range. In this talk, I will discuss our recent work on lateral spin transport devices where a buried SiO2 native oxide serves as a gate dielectric to electrostatically control the proximity of spin-polarized conduction electrons to the interface. Lattice inversion symmetry breaking, and/or coupling to paramagnetic defects, drastically affects the spin lifetime, as can be seen from time-of-flight distributions extracted from spin precession measurements. Effects seen in high magnetic fields further elucidate the mechanisms relevant to electron spin relaxation at this technologically important electronic interface.
Biographical Sketch:
Dr. Appelbaum is the author or co-author of over 40 peer-reviewed journal papers, recipient of the National Science Foundation CAREER award (2008) and the 2008 Outstanding Junior Faculty Member for the University of Delaware’s College of Engineering. Most notably, his group was the first to overcome significant electronic structure and materials challenges to demonstrate spin transport in silicon, resulting in a publication in Nature. His group then showed how this device design could be used as a spin field-effect transistor both theoretically and experimentally. Using these techniques, Appelbaum’s lab demonstrated spin transport through an entire 350-micron-thick silicon wafer, allowing spin lifetime measurement of over 500ns at 60K, two orders of magnitude higher than any other bulk material. These long lifetimes enable spin transport over millimeter lengthscales. More recently, they have achieved lateral spin transport in electrostatically-gated Si devices, and continue to investigate the role of semiconductor/insulator interfaces and reduced dimensionality on electron spin relaxation and dynamics.