2012 – 2013 IMR Colloquia Series
The Institute for Materials Research hosts a colloquia series each academic year, bringing international materials experts to Ohio State to share the latest findings in their research. Details about the colloquia offered during the 2012-2013 academic year are below. All colloquia are free and open to the entire OSU materials community – faculty, staff, and students.
For a detailed listing of all past IMR Colloquia since 2007, click here.
Two-Dimensional Electron Gases at Complex Oxide Interfaces
Susanne Stemmer, Professor, Materials Department, University of California Santa Barbara
11:15 AM – 12:15 AM (Light reception to follow)
Abstract: Two-dimensional electron gases at interfaces between two insulating oxides have attracted significant attention because they can exhibit unique properties, such as strong electron correlations, superconductivity and magnetism. In this presentation, we will discuss an example for such an interface, between the strongly correlated Mott insulator GdTiO3 and the band insulator SrTiO3. A fixed polar charge exists at these interfaces because of a polar discontinuity at the interface. The interfacial charge can be compensated by a high-density, two-dimensional electron gas (2DEG). At GdTiO3/SrTiO3 interfaces grown by molecular beam epitaxy, this results in a high-density 2DEG, of approximately 1/2 electron per surface unit cell, or 3×1014 cm-2, for all GdTiO3/SrTiO3 heterostructures, independent of the individual layer thicknesses and growth sequences. We will present measurements of quantum oscillations that provide insights into the nature of a 2DEG derived from the Ti d-states. We will report on electron correlation effects, such as magnetism and mass enhancement, in extremely high carrier density SrTiO3 quantum wells that can be obtained using these interfaces. Finally, we discuss the potential of oxide heterostructures for future electronic devices. The work was done in collaboration with Pouya Moetakef, Clayton Jackson, Tyler Cain, Leon Balents, Jim Allen, Jimmy Williams and David Goldhaber-Gordon.
Speaker Bio: Susanne Stemmer is Professor of Materials at the University of California, Santa Barbara. She received her Diploma in Materials Science from the Friedrich-Alexander University Erlangen-Nürnberg (Germany) and did her doctoral work at the Max-Planck Institute for Metals Research in Stuttgart (Germany). She received her doctoral degree from the University of Stuttgart in 1995. Following several postdoctoral positions she held an Assistant Professor position in Materials Science at Rice University from 1999 to 2002. In 2002, she joined the University of California, Santa Barbara, where she was promoted to Full Professor in 2008. Her research interests are in transmission electron microscopy techniques, in particular, the development of scanning transmission electron microscopy as a quantitative tool in materials science, novel dielectrics, oxide thin film growth and correlations between microstructure and electronic, dielectric and transport properties of oxide heterostructures. She has authored or co-authored more than 150 publications. Honors include an NSF Career Award, Fellow of the American Ceramic Society and Fellow of the American Physical Society.
Director of Photonics and Microelectronics Laboratory, Distinguished Professor of Engineering, Carolina Distinguished Professor, University of South Carolina Department of Electrical Engineering
Thursday, October 4, 2012
Abstract: AlInGaN materials and devices research has come a long ways since its infancy days in the early 80′s. High power visible light emitting diodes and lasers have already become a multi-billion dollar business. For the power electronics market place, several large companies are now introducing components and modules based on AlInGaN HEMTs. There are all the indications that high-efficiency AlInGaN based electronic devices will also be a key player in these very large rf- and the low-frequency power electronics’ markets. In this presentation we will review the recent progress and discuss the emerging trends in the AlInGaN Optical and Electronic devices’ research. Our pioneering research at the University of South Carolina which led to the first demonstration and the improvement of power-lifetime performance in deep UV Light emitting diodes for air-water purification and bio-medical instrumentation will be discussed. Some of our recent work in insulating gate-enhancement mode AlIN-GaN HEMTs on silicon and other substrates will also be reviewed. In addition we will describe the innovative material growth strategies that led to low-defect epi-structures which are key to yielding the improved performance in AlInGaN Optical /Electronic devices.
Bio: Dr. Asif Khan is a Professor of Electrical Engineering and is the founding Director of the Photonics & Microelectronics Laboratory at the University of South Carolina. He has served as Professor (1997-present) and Department Chair (2001-2006) during his tenure. His research focus at USC is on the fabrication of GaN-AlGaN based high power microwave transistors and deep ultraviolet light emitters. A graduate of MIT, Dr. Khan has also worked for Honeywell, 3M, and a startup APA Optics. He has authored over 400 refereed papers, several book chapters, over 100 invited papers, and more than thirty patents. Among a long list of honors and awards, he has been selected as an IEEE Fellow, Plenary Speaker for numerous conferences and a DARPA Award for Outstanding Performance. He was also awarded Best Research Paper of the year in 2004 and 2006 by the Japanese Applied Physics Society, an honor given for pioneering research in AlInGaN LEDs. Dr. Khan’s resume has a long list of “Firsts” in research accomplishments as well as significant commercial products to his credit. His research groups pioneered GaN-Electronics and deep-ultraviolet LEDs. These products have blossomed into billion dollar industries. Dr. Khan was a founding member of two startups in Columbia SC namely SET Inc and Nitek Inc. These startups have led to more than 100 high-tech jobs in the state of South Carolina. They also provide excellent job opportunities for USC graduates thereby keeping their talents locally.