Séminaire Informel DQMP - Nanoscale and Nano-Volumetric Materials Properties of Functional Materials and Photovoltaics via High Speed and Tomographic AFM

23.07.2019 10:00 – 12:00

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 areal resolution, we developed High Speed Atomic Force Microscopy as well as several new variations of photoconductive AFM. 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 reported efficiency for a magnetoelectric switch (Heron et. al., Nature, 2014). And for polycrystalline solar cells, novel photovoltaic performance maps reveal order-of-magnitude inter- and intra- granular heterogeneities (Atamanuk, Beilstein J. Nanotech, 2019). 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 Tomographic AFM for photocurrent as well as piezoelectric domain mapping, 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, TAFM literally uncovers new pathways to improve carrier separation (Luria et. al., Nature Energy, 2017). For BiFeO3, Tomographic AFM confirms Kay-Dunn thickness scaling, LGD behavior with a minimum switchable thickness of

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Bâtiment: Ecole de Physique

Salle MaNEP

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