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Atomic and electronic structure characterization of two-dimensional transition metal dichalcogenides
时间:2018-10-29 14:06:00    来源:超级管理员组       阅读:

二维过渡金属硫化物的原子和电子结构表征

洪金华 (Jinhua Hong)

材料科学工学博士。浙江大学物理系本科,于2011年取得理学学士学位后进入浙大材料学院直博,在电子显微学专家张泽院士、金传洪教授以及约克大学物理系袁俊教授的指导下,于2016年在浙江大学电镜中心取得工学博士学位。而后分别在日本名古屋精细陶瓷中心JFCC(2016.11-2017.9)和比利时安特卫普大学物理系电镜中心EMAT(2017.9-)进行博士后研究。

研究兴趣主要在低维纳米材料的电子显微学表征,通过球差矫正透射电镜表征纳米材料的原子结构、缺陷和晶面结构等;通过电子能量损失谱测量物质的化学组成、价电子激发、光吸收和等离子共振等物理特性。主要研究结果集中在过渡金属硫化物体系,以第一作者发表在Nat. Commun. (280次引用,2015年度中国百篇最具影响国际学术论文),Adv. Mater. (170次引用), Nano Lett., ACS Nano, Nano Research, Nanoscale, Phys. Rev. B等国际期刊上,google scholar上个人索引统计总被引用达1100余次。

Abstract: Atomically thin transition metal dichalcogenides (TMDs) have recently attracted extensive research interests in condensed matter physics and materials science, owing to their unique opto/electronic, photonic, valleytronic and catalytic properties. In this presentation, I will show the electronic and atomic structure characterization of TMDs by aberration corrected TEM:

1) Angle-resolved electron energy loss spectroscopy (EELS). We systematically measure the anisotropic valence electron excitation in MoS2, where the in-plane/out-of-plane anisotropy of the optical absorption decreases dramatically and energy band extrema have asymmetric movements when the thickness of MoS2 increases from monolayer to multilayer.

2) Atomically resolved ADF-STEM imaging of different dominant atomic defects in monolayer MoS2. Sulfur vacancies are found to be the domiant point defects in monolayer MoS2 prepared by mechanical exfoliation and chemical vapor deposition (CVD), while antisite defects with Mo replacing S sublattice are the most common defects in physical vapor deposited (PVD) monolayers. Electric transport measurements and DFT calculations show that part of antisite defects are magnetic and decrease the electron mobility more severely than vacancies.

3) Tracking the migration of adatom and vacancy in monolayer MoS2, through observation of their ground/metastable states, with DFT calculation to reveal more detailed kinetic pathways.

4) Atomic structure of grain/domain boundaries in MoS2 and MoSe2. Dense network-like inversion domain boundaries were found in molecular beam epitaxial MoSe2. Both scanning tunneling spectroscopy (STS) and DFT calculation demonstrate these boundaries induce the metallic mig-gap states with considerable density of states, which will greatly enhance the d-band catalysis in hydrodesulfurization (HDS) and hydrogen evolution reaction (HER). These inversion domain boundaries result in diverse stacking orders in the bilayer MoSe2, with different band tail states measured by STS.

Following these results, further research prospects on two-dimensional materials are proposed, in terms of in-situ TEM and EELS characterization.

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