报告题目：Characterization of Energy Materials Using Transmission Electron Microscopy: Learning the Materials from the Bottom
时间：12月30日（周三） 10:00-11:30
地点：bw必威西汉姆联官网仙林校区bw必威西汉姆联官网亚原子分辨电镜实验室（天文空间学院旁）
Abstract
One of the greatest goals in materials science is to develop and utilize new materials to solve the energy problems that our mankind is facing in the new era. Exploration of the new materials has helped us to produce more sustainable energy resources and consume them more efficiently. In this context, characterization of two kinds of technologically important energy materials using a powerful technique- transmission electron microscopy (TEM), in order to learn their micro- and nano-structures, understand their growth mechanisms and optimize their physical properties, is presented in this talk.
The first material is the semiconductor gallium nitride (GaN) which is probably the most important semiconductor since Si due to its superior physical properties. Its successful application for blue light emitting diodes (LEDs) has been revolutionizing the way for lighting our world, and consequently the winning topic of the recent Nobel laureate. In this talk, I will give a brief overview of this material and focus on characterization of GaN and its alloys using TEM techniques. In particular, GaN grown eptaxially on a new substrate Ge has been studied extensively using conventional and advanced TEM techniques, providing an important insight to understand the structure of material as well as the growth mechanisms. Based on the TEM study, optimized growth conditions can be found, such that the crystal quality of GaN on Ge can be improved significantly.1,2 In addition, I will also talk about my research to explore the potential of GaN in photovoltics for next-generation high efficiency solar cells, in which aworking solar cell based on III-nitride thin films is demonstrated, and the link between the device performance and the structural defects in the material can be established through TEM characterization3.
The second material system is the nano-composites combining oxides and carbon-based nano-materials including carbon nanotubes (CNTs) and graphenes. The synergetic functions of the nano-composites exploiting the unique properties of each component allow for enhanced performance in many energy-related applications such as photo-catalysis, solar energy and batteries. In this talk, I will present my current research which is focused on TEM chacaterisation of TiO2 grown on CNTs and graphenes with atomic layer deposition (ALD). Applying advanced TEM techniques, the material system has been studied on a nano-meter and atomic scale, so that some fundamental questions regarding the structure and growth can be answered from the bottom4,5.
1 Zhang, Y. et al. Misoriented domains in (0001)-GaN/(111)-Ge grown by molecular beam epitaxy. Applied Physics Letters 91, doi:10.1063/1.2779099 (2007).
2 Zhang, Y. C., Fu, W. Y., Humphreys, C. & Lieten, R. Structural Characterisation of Improved GaN Epilayers Grown on a Ge(111) Substrate. Applied Physics Express 4, 3, doi:10.1143/apex.4.091001 (2011).
3 Zhang, Y. et al. The effect of dislocations on the efficiency of InGaN/GaN solar cells. Solar Energy Materials and Solar Cells 117, 279-284, doi:10.1016/j.solmat.2013.06.022 (2013).
4 Zhang, Y. et al. Growth and characterization of CNT-TiO2 heterostructures. Beilstein Journal of Nanotechnology 5, 946-955, doi:10.3762/bjnano.5.108 (2014).
5 Zhang, Y. et al. Understanding and Controlling Nucleation and Growth of TiO2 Deposited on Multiwalled Carbon Nanotubes by Atomic Layer Deposition. Journal of Physical Chemistry C 119, 3379-3387, doi:10.1021/jp511004h (2015).
Brief Bibliography
Dr. Yucheng Zhang graduated with a B.Sc degree in Materials Science from Harbin Institute Technology (HIT) in 2001. He obtained a M.Sc degree in Queen Mary, University of London (QMUL) in 2003, a MPhil degree in 2004 and then a PhD degree in 2008 at University of Cambridge. After that he continued as a post-doctoral researcher in the same research group until 2013 when he moved to the current position at EMPA, the Swiss Federal Laboratory of Materials Science and Technology, working as a research scientist. His research has been focused on characterization of functional materials using conventional and advanced transmission electron microscopy (TEM) techniques. He has participated in several projects within the European research framework and published over 30 papers. His full research profile can be found at Researchid:
https://www.researchgate.net/profile/Yucheng_Zhang7?ev=prf_highl
