Colloquium
Department of Physics, NCU
2D materials: from electron microscope’s point of view
Speaker
Dr. Yung-Chang Lin
National Institute of Advanced Industrial Science and Technology (AIST), Japan
Date 2014.11.18(Tue)
Time 14:00
Place S4-625
「歡迎大學部同學參加，可獲得中大護照認證2小時」
The scanning transmission electron microscope (STEM) is an extremely powerful tool for the characterization of nanostructures, providing structure information at atomic precision, the single-elemental composition and electronic configuration at ultimate sensitivity. In the recent ten years, two-dimensional (2D) materials began to isolate from bulk crystals and present wide variety of properties including, for example, zero-gap semiconducting graphene, the insulating h-BN, direct band gap semiconductor MoS2, WS2, and superconducting NbS2, TaS2.
In this talk, we will present our recent findings on the use of in situ STEM to record the dynamics of structure transformation [1], defect migration [2,3], phase transition [4], and recrystallization [5] in 2D materials such as graphene, h-BN, and transition metal dichalcogenides. We also demonstrate the utmost sensitive electron energy loss spectroscopy studies on specific edge structures [6], dopant atoms and point defects in 2D materials [7].
References:
[1] Y. C. Lin, T. Björkman, H. P. Komsa, F. S. Huang, C. H. Yeh, K. H. Lin, J. Jadczak, Y. S. Huang, P. W. Chiu, A. V. Krasheninnikov, and K. Suenaga, “Rotational defects in two-dimensional transition metal dichalcogenides: a new class of point defect governed by crystal symmetry”, submitted, (2014).
[2] Y. C. Lin, D. O. Dumcenco, H. P. Komsa, Y. Niimi, A. V. Krasheninnikov, Y. S. Huang, and K. Suenaga, “Properties of individual dopant atoms in single-layer MoS2: atomic structure, migration, and enhanced reactivity”, Adv. Mater. 26, 2857-2861 (2014).
[3] O. Cretu, Y. C. Lin, and K. Suenaga, “Evidence for active atomic defects in monolayer hexagonal boron nitride: A new mechanism of plasticity in two-dimensional materials”, Nano Lett. 14, 1064-1068 (2014).
[4] Y. C. Lin, D. O. Dumcenco, Y. S. Huang, and K. Suenaga, “Atomic mechanism of the semiconducting-to-metallic phase transition in single-layered MoS2”, Nat. Nanotech. 9, 391-396 (2014).
[5] Z. Liu, Y. C. Lin, C. C. Lu, C. H. Yeh, P. W. Chiu, S. Iijima, and K. Suenaga, “In situ observation of step-edge in-plane growth of graphene in a STEM”, Nat. Comm. 5, 4055 (2014).
[6] J. Warner, Y. C. Lin, K. He, M. Koshino, and K. Suenaga, “Atomic level spatial variations of energy states along graphene edges”, Nano Lett. DOI: 10.1021/nl5023095 (2014).
[7] J. Warner, Y. C. Lin, K. He, M. Koshino, and K. Suenaga, “Stability and spectroscopy of single nitrogen dopants in graphene at elevated temperatures”, ACS Nano in press, (2014).