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Winter Seminar: Monday, March 11, 2013

Nanoscale strain engineering for energy

Marina S. Leite

CNST, National Institute for Standard and Technologies

Maryland Nanocenter, University of Maryland

Date: Monday, March 11th                Location: Bannan Hall 238                            Time: 4:00 ? 5:00

ABSTRACT: The ability of controlling strain at the nanoscale governs numerous materials? properties, from structural morphology of solid-state batteries to band gap engineering for photovoltaic devices. Depending on the mechanical strain between a substrate and an epitaxially grown material, different morphologies can be achieved ranging from strained planar films to 3-dimensional nanocrystals. In this talk, I will discuss how strained nanoarchitectures can be used for improved energy generation and storage applications. First, I will discuss the driving forces for alloying in quasi-equilibrium Ge-Si nanocrystals, which results primarily from entropy. I will describe experiments in which we tailored adatoms diffusion mechanisms to achieve both open and closed thermodynamic systems at the nanoscale. Second, I will discuss the role of strain engineering in thin films to achieve >50% multjunction solar cells with optimized bandgap energies. I will also discuss how we can resolve the photo-electronic properties of thin film solar cell technologies using near field scanning probe techniques. Such measurements help elucidate the main limitations of these devices, which currently dominate the PV market. Lastly, I will discuss design alternatives for tailoring the anode structural properties of solid-state thin film batteries to extend their lifetimes and improve their performance.

BIO: Marina Leite is a CNST/UMD Research Associate in the Energy Research Group. She received her B.S. in Chemistry in 2003 and her Ph.D. in Physics from Universidade Estadual de Campinas (UNICAMP), Brazil, in 2007. She was a postdoctoral scholar in the group of Harry Atwater in the departments of Applied Physics and Materials Science at Caltech until 2011 when she moved to NIST. Her research interests include multijunction solar cells, nanoscale-resolution measurement techniques for photovoltaic materials, epitaxial quantum dots for solar cells, and solid-state batteries. Marina has published in journals such as Phys. Rev. Lett., Adv. Mat., and Appl. Phys. Lett., and received a number of recognitions, including from The International Union of Pure and Applied Physics (IUPAP).