Lensless Imaging of Atomic Surface Structures via Ptychography

Monday, August 12, 2013 - 11:00am

Presented by Chenhui Zhu
Materials Science Division, Argonne National Laboratory, Argonne, IL 

Coherent x-ray diffraction imaging (CDI) is a lensless technique, which has been in rapid progress recently due to its great potential for high spatial resolution and in-situ measurement. We demonstrate by numerical simulation that atomic structures on single crystal surface can be reconstructed using the ptychography CDI. Our approach is based on the concept of crystal truncation rod. We can obtain the highest surface sensitivity at anti-Bragg condition, and achieve a phase contrast up to π from a single atomic step. Ptychograhy scanning scheme allows us to overcome the stringent requirement for isolated samples in typical CDI experiments. We will show experimental results from real platinum (001) surfaces and their ptychography reconstructions. This approach opens many opportunities, such as in-situ monitoring of atomic surface structures of single crystal catalysts in extreme conditions, thin film growth and nano-science applications. 

In the second part of my talk, I will briefly introduce a few liquid crystal phases, including (a) ferroelectric orthogonal smectic (lamella) phases, which exhibits sub-microsecond fast switching under electric field; (b) nanophase segregation and the robust nanofilament structure in binary liquid crystal mixtures.

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