MRS Bulletin

Technical Feature

Technical Feature

Aspects of Thin-Film Superlattice Thermoelectric Materials, Devices, and Applications

Harald Böttner, Gang Chen and Rama Venkatasubramanian

Abstract

Superlattices consist of alternating thin layers of different materials stacked periodically.The lattice mismatch and electronic potential differences at the interfaces and resulting phononand electron interface scattering and band structure modifications can be exploited to reduce phonon heat conduction while maintaining or enhancing the electron transport.This article focuses on a range of materials used in superlattice form to improve the thermoelectric figure of merit.

Keywords

  • thermal conductivity;
  • thermoelectricity

Harald Böttner is deputy head of the Components and Microsystems Department of the Fraunhofer Institute for Physical Measurement Techniques in Freiburg, Germany, and is currently responsible for its thermoelectric activities. He graduated with a diploma degree in chemistry from the University of Münster in 1974 and received his PhD degree in 1977 at the same university for his thesis on diffusion and solid-state reaction in the quaternary semiconductor II–VI/IV–VI material system. He joined the Fraunhofer Institut für Silicatforschung in 1978 and accepted his present appointment in 1980. He developed IV–VI infrared semiconductor lasers in parallel with activities in thermoelectrics until 1995, when he became responsible for the development of semiconductor gas sensors and thermoelectric materials until 2003. Böttner's current research activities focus on thin-film and nanoscale thermoelectrics and microelectronicsrelated device technology. He is the author or co-author of more than 100 publications, holds more than 10 patents, and is a member of the board of the International Thermoelectric Society.

Böttner can be reached at Fraunhofer IPM, Research Field Thermoelectrics, Heidenhofstrasse 8, 79110 Freiburg, Germany; tel. 49-761-8857121 and e-mail harald.boettner@ipm.fraunhofer.de.

Gang Chen is a professor of mechanical engineering at the Massachusetts Institute of Technology. He received his BS (1984) and MS (1987) degrees from the Power Engineering Department at Huazhong University of Science and Technology, China, in 1984 and 1987, respectively, and his PhD degree in mechanical engineering from the University of California, Berkeley, in 1993. He was an assistant professor at Duke University from 1993 to 1997 and an associate professor at the University of California, Los Angeles, from 1997 to 2001. His research interests center on microelectronics thermal management and nanoscale transport phenomena, particularly nanoscale heat transfer, and their applications in energy storage and conversion.

Chen is a recipient of a K.C. Wong Education Foundation fellowship, an NSF Young Investigator Award, and a John Simon Guggenheim Foundation fellowship. He serves on the editorial boards of Annual Review of Heat Transfer, the Journal of Computational and Theoretical Nanoscience, the Journal of Nanomaterials, and Microscale Thermophysical Engineering. He also serves as the chair of the Advisory Board of the ASME Nanotechnology Institute and on the advisory boards of several organizations.

Chen can be reached at the Massachusetts Institute of Technology, Department of Mechanical Engineering, Room 3-158, 77 Massachusetts Avenue, Cambridge, MA02139-4307, USA; tel. 617-253-0006 and e-mail gchen2@mit.edu.

Rama Venkatasubramanian is director of the Center for Thermoelectric Research at RTI International in North Carolina and the founder and chief technology officer of Nextreme Thermal Solutions Inc., a company spun off from RTI to commercialize its unique thin-film superlattice thermoelectric technology. He earned his PhD degree in electrical engineering from Rensselaer Polytechnic Institute and is a National Talent Scholar and a graduate of the Indian Institute of Technology in Madras. His research interests include photovoltaics, heteroepitaxy of novel materials, photonic materials, the study of nanoscale thermal physics, thermal management in highperformance electronics, and direct thermal-toelectric conversion devices. He is well known for pioneering thermoelectric superlattice materials and devices. Venkatasubramanian's work on superlattices has been recognized as a significant breakthrough in thermoelectrics using nanoscale engineered materials. This technology has won an R&D 100 Award (2002) and the Technology of the Year Award (2005) from the Council for Entrepreneurial Development in North Carolina.

Venkatasubramanian is a recipient of the Allen B. Dumont Prize from Rensselaer, RTI's Margaret Knox Excellence Award in Research in 2002, and the IEEE Eastern North Carolina Inventor of the Year in 2003. He has several patents issued in thermoelectrics, has authored more than 100 refereed publications, and has contributed to two book chapters.

Venkatasubramanian can be reached at RTI International, Center for Thermoelectric Research, PO Box 12194, Research Triangle Park, NC 27709-2194, USA; tel. 919-541-6889 and e-mail rama@rti.org.

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