学术报告:液体及固体表面界面研究等报告

2017/04/28 | 【 【打印】【关闭】 | 访问次数:

报告时间:2017年5月4日(星期四) 下午14:00

报告地点:张江科研楼303会议室

 

日程 报告人 题目
14:00-14:40 Dr. Binhua Lin
CARS, University of Chicago
Opportunities for Studying Liquid Interfaces at Synchrotrons:Liquid Interfaces as Controlled Model Systems for Understanding Chemical and Materials Processes
14:50-15:30 Dr. Hua Zhou
Staff physicist,Advanced Photon Source (APS)
Atomic Imaging Oxide Heterostructures and Interfaces by Phasing Coherent Bragg Rods for Electronic and Energy Systems
15:40-16:20 Dr. Huajun Liu
Institute of Materials Research and Engineering, A*STAR, Singapore
Developing Synaptic Electronics for Neuromorphic Computing – Role of Synchrotron X-ray Studies

报告简介: 
1、Binhua Lin 
Liquid interfaces provide a dynamic platform for the assembly of soft materials. A known molecular composition can be added to the interface, the surrounding environment can be controlled (pH, ionic content, temperature, viscosity, interfacial electric potential), the interfacial density varied, and molecular species can be added to the neighboring bulk phases to bind to or chemically interact with the assembly in a controlled manner. The dynamic re-organization of the interfacial assembly in response to these perturbations provides a paradigm for materials interactions that mimic similar dynamic structure in bio-systems. Understanding the fundamental microscopic structure of liquid interfaces, and molecular films confined to these interfaces, is essential to address many technological issues faced by the world, including those in energy, health and the environment. Synchrotron x-ray surface scattering techniques are the tool of choice for structural investigations of liquid surfaces and interfaces by virtue of their sensitivity to atomic and molecular length scales and their ability to distinguish the surface structure from that of the bulk. 
In this talk I will first present an overview of the liquid surface science program at ChemMatCARS (Sector 15 of the Advanced Photon Source, USA) with a few examples highlighting the work on: (1) phospholipid recognition in structural immunology; (2) liquid surface-enabled directed assembly of molecules and nanoparticles for tailored functionality; and (3) metal ion extraction at the liquid/liquid interface vital to environmental and radioactive waste cleanup. I will then describe a suite of techniques that are used in liquid surface scattering at our facility, including both established ones, such as X-ray reflectivity, grazing-incidence X-ray diffraction or grazing-incidence small-angle X-ray scattering, and off-specular scattering), as well as some newly developed ones, such as time-resolved measurements on the sub-minute time scale, surface fluorescence spectroscopy, resonant or anomalous surface scattering, and high energy pair-distribution function measurements. These techniques have been indispensable in the investigation of the fundamental science of soft interfaces and in the study of model systems for natural processes important in physical, chemical, biological, and technological systems. 

2、Hua Zhou
Dr. Hua Zhou is a staff physicist at the Advanced Photon Source (APS) in Argonne National Laboratory. He has managed a tunable undulator beamline and developed scientific programs dedicated for in-situ/operando and real-time X-ray studies of advanced materials synthesis, functionality and applications, in particular on surface/interface phenomena and processes in complex environments (e.g. thin film deposition of epitaxial nanostructures and heterostructures, emergent physics of strongly correlated condensed matters, versatile solid/liquid/gas interfaces for electrochemical energy storage and conversion systems) at the APS since 2011. He has extensive research experience using synchrotron-based X-ray techniques to characterize and uncover surface/interface structural modifications and dynamics of epitaxial thin films and heterostructures by using phase retrieval direct methods. As co-principal developer, he also participates in the design and construction of the coherent High Energy X-ray (CHEX) Sector for In Situ Studies for APS MBA-Lattice Upgrade project. Before he joined the APS, he was a postdoctoral fellow in National Synchrotron Light Source at Brookhaven National Laboratory and in Chemical Science and Engineering Division at Argonne National Laboratory. He received his Ph.D. degree in Materials Science from University of Vermont in late 2007. His work and contributions on thin films/heterostructures and surface/interface X-ray scattering techniques have been featured in book chapters, reviewers and more than 70 peer-reviewed publications including on high impact journals like Nature, Nature Physics, PNAS, Physical Review Letters, Energy and Environmental Science, Advanced Materials, Advanced Functional Materials, Nano Letters, and ACS-Nano etc. He has presented more than 20 invited speeches in international conferences, university and national lab seminars and lectures. 

3 Huajun Liu
Neuromorphic computing is a promising future computing technology that emulates neural networks in human brain for adaptive and parallel computing with low energy consumption. To develop brain-inspired electronics for neuromorphic computing, however, understanding of fundamental device mechanism is an essential prerequisite. Synchrotron X-ray based scattering, spectroscopic and imaging techniques are very powerful tools that can provide key information on both atomic and electronic structures of novel materials for neuromorphic computing devices. The special advantage of synchrotron X-ray studies is the flexibility and accessibility for in operando experiments, where the structural evolutions can be monitored real time in operating devices. 
Here I will show two examples of synchrotron X-ray studies on neuromorphic devices at Advanced Photon Source, Argonne National Laboratory. In the first work, dynamic defect behavior in an artificial synapse made of memristive device is imaged by synchrotron x-ray multimodal microscopy. We demonstrated experimental observation of fully quantitative oxygen vacancy profile and its correlations to the change of resistance states as the conduction channel is formed and reversible switched during device operation. Our results clearly demonstrate how distinct macroscopic electrical states can arise from nanoscale changes in oxygen stoichiometry and suggest a strategy exploiting the collective behavior of functional ionic defects to develop brain-inspired electronics for neuromorphic computing. In the second work, the structural origin of resistance modulation by electric field applied through ionic liquid gating is investigated. In situ X-ray scattering of half-order reflections shows the oxygen octahedral tilt angles are reversibly tunable by applied electric fields, leading to metallization of initially insulating oxide film. X-ray absorption spectroscopy reveals the role of oxygen vacancies in facilitating the octahedral rotation. This work opens the door of dynamically control oxygen octahedral connectivity in perovskite oxides to design oxide electronics that mimic synaptic spike-timing-dependent learning behavior. 

Biography 
Huajun Liu is a materials scientist at Institute of Materials Research and Engineering (IMRE), A*STAR, Singapore. He obtained his B. S. from University of Science and Technology of China in 2008 and Ph. D. from National University of Singapore in 2012. He did postdoctoral studies at Argonne National Laboratory, USA, where he developed in-situ x-ray microscopy for simultaneous structural and chemical imaging of working electronic devices at Advanced Photon Source. He has also been working on ferroelectric, multiferroic and memristive epitaxial oxide thin films, focusing on understanding fundamental mechanism by surface x-ray scattering, absorption spectroscopy and in-situ multimodal imaging. He received numerous awards including President’s Graduate Fellowship and A*STAR International Fellowship.
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