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[2018 05 04] 특별세미나 _Dr. Hyobin Yoo (Harvard Univ.)

Electron microscopy and electrical transport study of interfacial reconstruction in 2-D materials

관리자 | 2018.05.03 09:48 | 조회 341


Electron microscopy and electrical transport study of interfacial reconstruction in 2-D materials

 

 Date: 2018. 05. 04(Fri) , 11:00 ~ 12:30

 Place: Science Building, Room.301 Multimedia Room

 Speaker: Dr. Hyobin Yoo (Harvard Univ.)

Host of a Seminar: Prof. Moon-Ho Jo

Abstract:

 

Interfaces between crystalline materials have been an essential engineering platform for modern electronics. At the interfaces in two-dimensional (2D) van der Waals (vdW) heterostructures, the twist-tunability offered by vdW crystals allows the construction of a moiré superlattice, leading into exotic physical phenomena.1 However, these interfaces exhibit more intriguing structures than the simple moiré superstructure. Despite the weak nature of vdW interaction and the absence of dangling bonds, substantial lattice reconstruction can occur at vdW interfaces, revealing spatially varying atomic registry. Since the electrical transport behavior is sensitive to changes in local atomic structure, comprehensive study of electrical transport in conjunction with multiscale structural analysis is necessary. To understand the impact of the interfacial reconstruction on the transport properties, we combine transmission electron microscopy (TEM) with quantum electrical transport measurement. First, the interlayer stacking angle at the vdW interface is engineered in artificial bilayer graphene and transition metal dichalcogenides.2,3 Periodic arrays of commensurate domains were identified, which provide topologically non-trivial transport channels along the domain boundaries. The quantum electronic transport measurement reveals that the engineered interfacial reconstruction can provide essential elements for valleytronics application.

If time allows, I will briefly discuss our recent efforts to develop novel method to combine TEM analysis with electrical measurement in a single platform. Fabrication of micro- and nanodevices on thin membrane and suspended structure allows direct structure/property correlation.4 Such TEM device chip can provide useful tools for electrical/structural nano-characterization of materials and can be also employed to study the dynamics of materials in the future.

 

1. Y. Cao, V. Fatemi, S. Fang, K. Watanabe, T. Taniguchi, E. Kaxiras, P. Jarillo-Herrero, Unconventional superconductivity in magic-angle graphene superlattices, Nature 556, 43 (2018)

2. H. Yoo, K. Zhang, R. Engelke, P. Cazeaux, S. H. Sung, R. Hovden, A. W. Tsen, T. Taniguchi, K. Watanabe, G.-C. Yi, M. Kim, M. Luskin, E. B. Tadmor, P. Kim, Atomic reconstruction at van der Waals interface in twisted bilayer graphene, submitted (arxiv: 1804.03806).

3. H. Yoo, J. Jobst, T. D. Jong, R. Engelke, S. J. Molen, P. Kim, Engineering domain topology and symmetry in twisted bilayer transition metal dichalcogenides, in preparation.

4. D. K. Bediako, M. Rezaee, H. Yoo, D. T. Larson, S. Y. F. Zhao, T. Taniguchi, K. Watanabe, T. L. Brower-Thomas, E. Kaxiras, P. Kim, Heterointerface effects in the electro-intercalation of van der Waals heterostructures, Nature, in press (2018).

 

Dept. of MSE / BK21+






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