特邀专家: 韩勇博士

美国国家能源部埃姆斯实验室（Ames Laboratory,U. S. Department of Energy）以及爱荷华州立大学（IowaStateUniversity）物理系

报告题目： Nucleation and Growth Kinetics for Intercalated Islands during Deposition on Layered Materials

时间：2018年4月16日（星期一）上午10:00

地点：beat365在线登录平台东区三教149

报告人学术背景及科研方向简介:

2012年至今，Staff Assistant Scientist，美国国家能源部埃姆斯实验室（Ames Laboratory,U. S. Department of Energy）以及爱荷华州立大学（IowaStateUniversity）物理系。2011至2012年，Staff Assistant Scientist,爱荷华州立大学物理科学技术研究所（Institute for Physical Research and Technology）。2011年4月至8月, Visiting Scientist，北京计算科学研究中心。2007至2011年，Postdoctoral Research Associate, 爱荷华州立大学物理科学技术研究所以及美国国家能源部埃姆斯实验室。研究方向为利用现代超级计算机、密度泛函理论、动力学蒙特卡洛模拟技术以及各种物理模型对纳米结构材料进行计算机模拟以及理论分析，主要集中在与材料表面（或界面）、薄膜相关的热力学和动力学，以及纳米结构材料（纳米膜、纳米线、单原子链、纳米管、纳米簇、石墨烯、二维材料、拓扑绝缘体表面等等）本身丰富的电子性质。研究也涉及纳米结构材料（包括单原子或分子）在衬底材料表面的吸附、宏观电磁现象以及微观电子结构的理论分析等等。目前已在Physical Review Letters, Physical Review B, Nano Letters, PNAS, Applied Physics Letters, Journal of Chemical Physics, Journal of Physical Chemistry Letters, Journal of Physical Chemistry C等国际著名杂志发表论文60多篇，也被邀请作为30多个国际著名杂志的审稿人。2001 年8月至2006 年12月，在美国犹他大学（University of Utah）物理系、材料科学与工程系学习并获物理学硕士学位和材料科学与工程博士学位。 1997 年7月至2001 年7 月，在beat365在线登录平台物理系工作，研究方向为理论核结构物理。 1994 年9 月至1997年7 月，在beat365在线登录平台物理系学习并获理学硕士学位。

报告简介：

Intercalation is a way to alter or tune the transport and magnetic properties of a bulk compound over a wide range.Compounds formed by metals in bulk graphite are particularly well-known where the intercalants are alkali metals, alkaline earths, and rare earths. However, intercalation at surfaces of bulk layered compounds has received very little attention.It is desirable to produce new surface properties in catalysis, magnetism, or friction at the surface of a cheap, robust, and plentiful material, such as graphite.Some elements, such as rare earths, are notably susceptible to oxidation, benefiting from protection by a two-dimensional layer of a layered material.In this report, I will present the theory and stochastic lattice-gas modeling, which is developed for the formation of intercalated metal islands in the gallery between the top layer and the underlying layer at the surface of layered materials. Our model for this process involves deposition of atoms, some fraction of which then enter the gallery through well-separated pointlike defects in the top layer. Subsequently, these atoms diffuse within the subsurface gallery leading to nucleation and growth of intercalated islands nearby the defect point source. For the case of a single point defect, continuum diffusion equation analysis provides insight into the nucleation kinetics. However, complementary tailored lattice-gas modeling produces a more comprehensive and quantitative characterization. We analyze the large spread in nucleation times and positions relative to the defect for the first nucleated island. We also consider the formation of subsequent islands and the evolution of island growth shapes. The shapes reflect in part our natural adoption of a hexagonal close-packed island structure. Motivation and support for the model is provided by scanning tunneling microscopy observations of the formation of intercalated metal islands in highly-ordered pyrolytic graphite at higher temperatures.

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beat365在线登录平台物理科学与技术学院

2018年4月12日