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Scattering and Instrumentation Sciences

Programs

Ultrafast Materials Science

Program Leader:  Alessandra Lanzara
Co-PIs: Joel Moore

This program seeks to investigate the properties of strongly correlated materials by shining light onto them. Intense laser pulses have been used to restructure the free-energy landscape of these materials, and to generate rapid switching between the various forms of order deriving from the strong correlation. State of the art highs harmonic generation photoemission spectroscopy and time- and spin- resolved photoemission spectroscopy systems have been developed. The future goal is to stimulate materials at selective excitations with higher intensity laser pulses to establish a mean for manipulation and control of materials properties.

Publications:

J.-H. Buss, H. Wang, Y. Xu, J. Maklar, F. Joucken, L. Zeng, S. Stoll, C. Jozwiak, J. Pepper, Y.-D. Chuang, J.D. Denlinger, Z. Hussain, A. Lanzara, and R.A. Kaindl. A setup for extreme-ultraviolet ultrafast angle-resolved photoelectron spectroscopy at 50-kHz repetition rate. Rev. Sci. Instrum. 90, 023105 (2019).

T.R. Xu, T. Morimoto, A. Lanzara, and J.E. Moore Efficient prediction of time- and angle-resolved photoemission spectroscopy measurements on a nonequilibrium BCS superconductor. Phys. Rev. B 99, 035117 (2019).

C. Hwang, W. Zhang, K. Kurashima, R. A. Kaindl, T. Adachi, Y. Koike, and A. Lanzara Ultrafast dynamics of electron-phonon coupling in a metal. EPL Europhys. Letters 126, 5700 (2019).

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Soft Matter Electron Microscopy

Program Leader: Nitash Balsara
Co-PI's: Xi Jiang, David Prendergast, Andrew Minor, Ronald Zuckermann

We aim to produce images of soft materials with atomic resolution using electron microscopy. This is inherently challenging because soft materials are unstable under the electron beam. To do so, we will design and implement a pre-specimen phase plate that takes advantage of a recently demonstrated scanning transmission electron microscopy (STEM) imaging mode that is more efficient than conventional high-resolution STEM. Sophisticated averaging algorithms will also be used to extract high resolution information from low exposure images, where Fourier transforms along orthogonal directions will be used to align individual images. To demonstrate these imaging concepts, we will use crystalline nanostructures formed by self-assembly of amphiphilic peptoid molecules in water. Of particular interest are structures formed by diblock copolypeptoids where conventional wisdom suggests that these molecules should form micellar aggregates with collapsed hydrophobic cores. In contrast, we obtain hollow crystalline tubes with hydrophobic groups exposed to water. Confirming this by atomic-scale imaging is important for a general understanding of molecular self-assembly. A series of peptoids with sequences of monomers specifically designed to enable high resolution electron microscopy will be synthesized by solid phase synthesis. Molecular dynamics will be used to characterize thermal fluctuations and disorder, and this information will be convoluted with the contrast transfer function of the microscope used in experiments to obtain theoretical images. This new framework for atomic resolution imaging on model peptoids will be applied to improve the resolution of electron microscopy of more conventional soft polymeric materials.

Publications

O. Panova, C. Ophus, C.J. Takacs, K.C. Bustillo, L. Balhorn, A. Salleo, N.P. Balsara, A.M. Minor. Diffraction imaging of nanocrystalline structures in organic semiconductor molecular thin films. Nature Materials, 2019, 18, pp. 860.

D.R. Greer, M.A. Stolberg, S. Xuan, X. Jiang, N.P. Balsara, R.N. Zuckermann. Liquid-Crystalline Phase Behavior in Polypeptoid Diblock Copolymers. Macromolecules, vol. 51, pg. 9519-9525, 2018.

X. Jiang, S.T. Xuan, J. Kundu, D. Prendergast, R.N. Zuckermann, N.P. Balsara. Effect of processing and end groups on the crystal structure of polypeptoids studied by cryogenic electron microscopy at atomic length scales. Soft Matter, 2019, 15, pp. 4723.

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In-Situ Liquid Cell Electron Microscopy: Atomic Level Heterogeneity and Fluctuations at Solid Liquid Interfaces

Program Leader: Haimei Zheng
Co-PI's: Emory Chan, Peter Ercius

The overarching goal of this program is to develop and utilize the advanced in-situ liquid cell transmission electron microscopy (TEM) to elucidate how atomic level heterogeneity and fluctuations at solid-liquid interfaces determine the physical and chemical properties and processes of materials, currently with a focus on nucleation, precipitation and dissolution at solid-liquid interfaces. With the development of liquid cell TEM, we investigate the transient nucleation events in an oversaturated solution and precipitation and dissolution at solid-liquid interfaces under an external stimulus, such as an electrochemical potential. Special attention will be made on correlation of concentration fluctuations to structural ordering during nucleation processes; characteristics of prenucleation clusters or intermediates; and how surface defects or inhomogeneity change the nucleation process and reduce the nucleation barrier. The development of advanced instrumentation for imaging and chemical identification with atomic resolution provides transformative opportunities for investigation of the dynamic phenomena at solid-liquid interfaces in this program and many other dynamic processes at the frontiers of basic energy science.

Publications

J. Yang, M. K. Choi, Y. Sheng, J. Jung, K. Bustillo, T. Chen, S.W. Lee, P. Ercius, J. H. Kim, J. H. Warner, E. M. Chan, and H. Zheng MoS2 liquid cell electron microscopy through clean and fast polymer-free MoS2 transfer. Nano Letters 19 (3) 1788 (2019).

Q. Zhang, G. Gao, G. Gao, Y. Shen, X. Peng, J. Shangguan, Y. Wang, H. Dong, K. Bustillo, L. W. Wang, L. Sun, and H. Zheng Anomalous shape evolution of Ag2O2 nanocrystals modulated by surface adsorbates during electron beam etching. Nano Letters 19, 591-597 (2019)

J. Yang, S. B. Alam, L. Yu, E. Chan, and H. Zheng Dynamic behavior of nanoscale liquids in graphene liquid cells revealed by in situ transmission electron microscopy. Micron 116, 22-29 (2019).

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