NG Microsystems Seminar: Rama Venkatasubramanian, "Nanostructured Thermoelectric Devices"
Tuesday, October 25, 2016
1146 A.V. Williams Building
Northrop Grumman Microsystems Seminar
Nanostructured Thermoelectric Materials and Devices
Rama Venkatasubramanian, Ph. D.
Team Leader, Energy & Thermal Management
Research & Exploratory Development Department
Johns Hopkins University Applied Physics Lab
Thermoelectric semiconductor materials and devices can enable a wide array of applications in solid state cooling of high-power electronics, IR-FPAs and compact air-conditioning systems as well as energy harvesting in many scenarios including solar-thermal, automotive exhaust heat, industrial waste heat, etc. One of the two major limitations in the widespread use of thermoelectric technology has been the materials figure of merit (ZT) and the other being the ability to translate the enhanced materials’ ZT to a device performance, overcoming various device electrical and thermal losses. These limitations have significantly curtailed the widespread use of semiconductor-based thermoelectric devices since their original development in 1950’s, at about the same time semiconductor-based transistors rose to prominence, even though they offer several other advantages like reliability, noise-free operation, and a green technology. Nanoscale materials based on superlattices, nano-dots, nano-wires and nano-bulk materials with second phases or nano-inclusions have become dominant approaches to enhancing the ZT in thermoelectric materials since 2001 (Nature 413, 597 (2001) and they have been further validated recently (Nature 451, 163 (2008), Nature 451, 168 (2008) and Science 320, 634 (2008)). Almost all of the recent successful efforts in ZT improvement have been a result of the significant reduction in lattice thermal conductivity through phonon scattering in nanostructures, without affecting the electrical transport of electrons or holes, by the so-called phonon-blocking electron-transmitting structures. Studies on the phonon-transport using femto-second optical and acoustic phonon property measurements have provided further understanding of the physics behind thermal conductivity reduction in superlattices. Careful band offset measurements have been carried out to understand and model carrier transport across interfaces in several superlattice systems. Device developments using advanced nanoscale superlattice thermoelectric materials, like hot-spot cooling of high performance electronics (Nature Nanotechnology 4, 235 (2009), power generation, and other biomedical applications will be presented.
Dr. Venkatasubramanian (Ph.D. Rensselaer, New York, 1988; B.S. IIT Madras, India, 1983; Electrical Engineering) is dedicated to the innovation and advancement of several solid state energy efficient materials and device technologies as well as transitioning them to DoD system integrators and industry. Dr. Venkatasubramanian is at the Johns Hopkins University, Applied Physics Lab (JHU/APL) as Team Leader for Energy and Thermal Management in the Research and Exploratory Development department. At JHU/APL, he is responsible for leading, initiating ideas, and collaborating with a team of engineers, senior scientists and other program management staff to develop advanced solid state energy technologies in thermoelectrics, photovoltaics, batteries and electronics thermal management for meeting the needs of US DoD and to position JHU/APL as a world-leading lab in advanced thermoelectrics. Until April 2013, Dr. Venkatasubramanian was the Senior Research Director of the Center for Solid State Energetics at RTI International, where he directed innovative basic and applied research in thermoelectrics, photovoltaics, and optoelectronic materials and devices for solid state energy conversion applications. Dr. Venkatasubramanian was the Founder and the Chief Technology Officer of Nextreme Thermal Solutions (2004-2006) which is commercializing technologies developed under his leadership with DARPA support; Nextreme was acquired by Laird Technologies in early 2013. Dr. Venkatasubramanian has over 115 peer-reviewed journal and conference publications, 17 issued patents, over 100 presentations in the area of thermoelectric materials and devices, photovoltaics, optoelectronics, and 5 book chapters and edited proceedings. Dr. Venkatasubramanian initiated and developed a research program focused on demonstrating the fundamental advantages of atomically engineered superlattices and other nanoscale materials; this research resulted in the first major breakthrough in the field of thermoelectrics in 40 years (Nature 2001, Nature Nanotechnology 2009) and has led to hundreds of laboratories around the world working on other nanoscale thermoelectric materials. Dr. Venkatasubramanian has received the R&D 100 Awards in 2002 and 2010 for thermoelectric innovations, the Margaret Knox Excellence Award for research at RTI in 2002 and Rensselaer’s Allen B. Dumont Prize for research achievements. Dr. Venkatasubramanian was elected Fellow of the IEEE (2011) and a Fellow of AAAS (2012) for seminal contributions to nanoscale thermoelectrics for thermal management of electronics and energy harvesting. Dr. Venkatasubramanian has also contributed to advances in multi-junction GaAs-based photovoltaics, has received a best paper award at the IEEE First World Conference and his work was recognized as key achievements by the US Department of Energy. Dr. Venkatasubramanian serves as an Editor of the IEEE Transactions on Electron Devices, has organized several symposia and has edited proceedings in thermoelectrics, energy harvesting and nanoscale thermal transport for the American Physical Society, Materials Research Society, IEEE and other professional societies.