MSE Colloquium: Chris Van de Walle, Oxides in Electronics

Abstract

Oxides have many applications, ranging from gas sensors to varistors.  They are increas-ingly being used in electronics and optoelectronics.  Transparent conducting oxides (TCOs) such as ZnO, SnO₂, and In₂O₃, provide metallic conductivity while absorbing little or no visible light; they are essential for devices such as solar cells, light-emitting diodes, and flat-panel displays.  TiO₂ has applications in solar cells and (photo)catalysis, and also, along with Al₂O₃, Ga₂O₃, SiO₂ and MgO, as a dielectric. Controllable p-type doping would in principle allow for optoelectronic devices such as light emitting diodes and detectors. And complex oxides such as SrTiO₃ and GdTiO₃ are being considered for next-generation electronics. Recent experimental progress has highlighted the fact that many fundamental aspects of oxides are still poorly understood.  I will discuss sources of conductivity, fundamental limits on optical transparency, difficulties in p-type doping, and localization of carriers, using a variety of technologically important oxides as examples.

Bio

Chris G. Van de Walle is a Professor in the Materials Department at the University of California, Santa Barbara.  Prior to joining UCSB in 2004, he was a Principal Scientist at the Xerox Palo Alto Research Center (PARC).  He received a Ph.D. in Electrical Engineering from Stanford University in 1986. He was a postdoctoral scientist at the IBM T. J. Watson Research Center in Yorktown Heights, New York (1986-1988); a Senior Member of Research Staff at Philips Laboratories in Briarcliff Manor, New York (1988-1991); and an Adjunct Professor of Materials Science at Columbia University (1991). He has published over 250 research papers, holds 22 patents, and has given over 125 invited and plenary talks at international conferences. His research interests include first-principles calculations for materials, defects and doping in semiconductors and oxides, surfaces and interfaces, and the physics of hydrogen in materials. Prof. Van de Walle is a Fellow of the American Physical Society, the Materials Research Society, the American Association for the Advancement of Science, and the AVS.  He is the recipient of a Humboldt Award for Senior US Scientist and the David Adler Award from the APS. He has chaired three conferences and was Program Chair for the 27th International Conference on the Physics of Semiconductors in 2004.