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Matthew Grayson

8:30 a.m.
May 25, 2007
Cook Hall Room 2058

Professor Matthew Grayson
Department of Electrical Engineering and Computer Science
Northwestern University
"Corner Overgrowth, Shadow Overgrowth, and Cleaved-Edge Overgrowth: Novel MBE Techniques for Embedded Heterostructures"
Three recent MBE growth technologies are reviewed which permit atomically precise engineering of non-planar heterojunction potentials. Such techniques have niche applications when non-planar confinement proves advantageous and some examples are shown. In corner overgrowth, two adjacent crystal facets are simultaneously overgrown under the same molecular flux, leading to L-shaped heterojunction potentials which nonetheless demonstrate high electron mobility. In shadow overgrowth, macroscopic high-purity pillars are placed in the path of the molecular beam in order to locally shadow selected molecular sources. Preliminary results on a shadowed superlattice demonstrate the proof of this principle. Finally, in cleaved-edge overgrowth, an in-situ cleaved sample is regrown on its cleave facet. Single- and double-cleave structures such as perpendicular quantum wells and vertical quantum wires are demonstrated. The first two techniques require only a special substrate holder to implement. The latter requires in addition a mechanical feedthrough to the growth chamber for a cleaving bar.

Born in St. Louis, Missouri, Matthew Grayson earned his PhD in 1998 with Dan Tsui at Princeton University on tunnel spectroscopy of quantum Hall effect edges. He then spent 2 years as a postdoc at the University of Maryland with Dennis Drew studying infrared spectroscopy of the Hall effect in high temperature superconducting thin films (YBCO). In 2000, he earned a Humboldt Fellowship for two years of research at the Tech. Univ. of Munich where he invented new growth techniques for GaAs based heterostructures. Subsequently he spent 3 months at the Max Planck Institut in Stuttgart in the group of Klaus von Klitzing before returning to the Tech. Univ. Munich, this time as a limited term assistant professor researching quantum transport under Gerhard Abstreiter. In March 2007 he began as an Asst. Professor in Electrical Engineering and Computer Science at Northwestern University.
Northwestern University Robert R. McCormick School of Engineering and Applied Science Electrical Engineering and Computer Science Department