Nanoscale and Nano-Volumetric Materials Properties of Functional Materials and Photovoltaics via High Speed and Tomographic AFM
Nano- and meso- scale materials properties are crucial to the macroscopic performance of a wide range of functional and photovoltaic devices. To directly and efficiently investigate such systems with nanoscale aerial resolution, we developed High Speed Atomic Force Microscopy as well as several new variations of photoconductive AFM. With piezoelectrics, geometric control is proven to locally enhance the converse-piezoelectric coefficient, with implications for a new class of transistors known as piezotronics (Keech et. al., Advanced Functional Materials, 2017). With ferroelectrics, movies of the domain switching process reveal unique nucleation and growth dynamics at grain boundaries and other microstructural defects (Huey et. al., J.A.Cer.S. cover article, 2012). Extending this approach to multiferroics, a stepwise polarization process was observed for the first time, enabling the development of the highest yet reported efficiency for a magnetoelectric switch (Heron et. al., Nature, 2014). And for polycrystalline CdTe solar cells, novel photovoltaic performance maps reveal order-of-magnitude inter- and intra- granular heterogeneities (Atamanuk, Beilstein J. Nanotech, in press). But ultimate device properties are equally sensitive to sub-surface effects, often with profound thickness dependencies related to microstructure and concentration, polarization, and/or field gradients. Therefore, we recently introduced Computed Tomographic AFM, achieving a 1,000,000x enhancement in resolution for volumetric materials property mapping. With CdTe, which already commands ~5% of the world ’ s solar cell market even though efficiency remains ~30-50% less than the theoretical limit, CTAFM uniquely reveals new proposed pathways to improve carrier separation (Luria et. al., Nature Energy, 2017). For BiFeO 3 , CTAFM confirms Kay-Dunn thickness scaling, LGD behavior with a minimum switchable thickness of <5 nm, and even 20 nm 3 domain and current tomography directly revealing the sub-surface domain structure and topological defects.
Bio and photo
Bryan Huey is a Professor and the Department Head of Materials Science and Engineering at the University of Connecticut. Bryan is the past chair of the 1200 person Basic Science Division of the American Ceramic Society, one of five overall organizers for the 7000 attendee 2019 MRS Fall Meeting, and co-organized previous EMA and US-Japan conferences. He is an expert in the development and application of advanced variations of Atomic Force Microscopy for studying piezoelectrics, multiferroics, photovoltaics, MEMS, and biological cells and tissue. This includes simultaneous AFM and 3d fluorescence, high speed AFM, PFM, and recently tomographic AFM.
Host: Prof. Tae Won Noh