Thermoelectric Transport in Nanostructures
Speaker: Mona Zebarjadi, MIT
Department: Mechanical & Aerospace Engineering
Location: Engineering Quadrangle J223
Date/Time: Wednesday, February 29, 2012, 12:30 p.m. - 1:30 p.m.
Thermoelectrics can directly convert heat into electricity and therefore have applications in waste heat recovery. These solid-state devices can also be integrated directly on chips and actively cool down hot spots of high-speed devices. In this talk, I will discuss modeling of electron and phonon transport inside thermoelectric legs to identify fundamental length scales such as carrier mean free path and momentum and energy relaxation lengths. Knowing the fundamental length scales, we can design nanostructured materials with enhanced thermoelectric figure of merit (Z=sS2/k). I will discuss strategies to reduce the thermal conductivity via introducing interfaces and rattling atoms to scatter phonons, to increase the electrical conductivity by means of modulation doping and to improve the Seebeck coefficient by energy filtering and introducing sharp features in the density of states. In each strategy the challenge is to improve one property without deteriorating the other properties. We have fabricated and characterized bulk samples as well as superlattices, which were designed based on different strategies. The obtained experimental results are in agreement with theoretical predictions but there is still a lot of room for improvement in terms of materials designing.
Mona Zebarjadi is a joint postdoctoral associate with Prof. Gang Chen (ME) and Prof. Mildred Dresselhaus (EE and Physics) in the Mechanical Engineering Department of the Massachusetts Institute of Technology were she is working on materials design and magnetotransport. She has defended her Ph.D. at the University of California, Santa Cruz in November of 2009. She was working in the quantum electronics group supervised by Prof. Ali Shakouri on characterization and simulation of transport properties in thermoelectric materials. Her research interests are in electron and phonon transport modeling, materials and device design, fabrication and characterization for energy conversion systems such as thermoelectrics, solar cells, and diffusion cells and heat management in high power electronics and optoelectronic devices.