세미나안내

[2015 04 03] 특별세미나 (BK21PLUS) Prof. Jaekwang Lee

Probing Defects using a Combination of Density-Functional Theory and Scanning Transmission Electron Microscope.

MSE Graduate Students and Researchers

관리자 | 2015.03.06 19:40 | 조회 4398


Date: 2015. 04. 03 (FRI), 16:00 ~ 

Place: Building, Room.202 Multimedia Room

Title: Probing Defects using a Combination of Density-Functional Theory and Scanning Transmission Electron Microscope.

Speaker: Prof. Jaekwang Lee (Pusan National University)

Host of a Seminar: Prof. Sang-Ho Oh

 

Abstract:

The combination of density functional theory (DFT) and scanning transmission electron microscopy (STEM) is a very powerful technique to directly investigate the structure, properties, chemistry and dynamics of defects1-5 in materials. Recently, two-dimensional materials such as graphene, hexagonal boron-nitride, and transition metal dichalcogenides have emerged among the hottest classes of materials owing to their promising properties for future applications. Here we report a direct, atomically-resolved observation of a single Si6 cluster trapped in a graphene nanopore. Though electron beams are known to induce irreversible atomic displacements, we first show that a 60 keV beam induces a reversible, oscillatory, conformational transformation: one of the Si atoms executes a back-and-forth motion between two sites within the Si6 cluster. Secondly, it has been observed that multivacancies in graphene are subject to reconstruction and partial or total filling by diffusing carbon adatoms (also known as the self-healing process). Stabilization of nanopores in graphene for extended periods of time has not yet been achieved. Here, using ab initio molecular dynamic simulation and STEM, we reveal that Si atoms successfully stabilize graphene nanopores by bridging dangling bonds along the perimeter of the pore.

 


Dept. of MSE / BK21+





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