Applied Microscopy

Korean Society of Microscopy (한국현미경학회)
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A Simulation Study of Atomic Resolution TEM images for Two Dimensional Single Layer and Bilayer Graphene Crystal

2차원적인 단층 및 복층 그래핀 결정에 대한 원자분해 투과전자현미경 영상 시뮬레이션 연구

  • 김황수 (경성대학교 이과대학 물리학과)
  • Received : 2010.02.16
  • Accepted : 2010.03.23
  • Published : 2010.03.31
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Abstract

In a simulation study of atomic resolution transmission electron microscope images of single layer and bilayer graphene, it is demonstrated that the conventional Bloch wave formulations can be used when high-order Laue zone reflections are properly taken into account in the theory. The simulated images for bilayer graphene show 3-fold rotational lattice symmetry rather than the 6-fold one under certain conditions. This result can be understood as revealed the 3-fold rotational lattice symmetry of bilayer graphene in three dimensions along [0001]. For single layer graphene the observed phase images showing 3-fold rotational lattice symmetry were particularly noted. This phenomenon has been explained by an assumption of the re-configuration of electron density on the surface of graphene. And the matching images have been obtained as simulated with up to the second order Laue zone reflections only, reflecting the re-configuration of electrons on the surface.

단층 및 복층의 그래핀에 대한 원자분해 투과전자현미경 영상 시뮬레이션 연구에서, 통상의 Boch-wave 방법에 의한 영상이론식들이 고 준위 Laue 영역의 역 격자 회절을 적절히 포함 했을 때 시뮬레이션에 잘 적용될 수 있음을 보여 주었다. 적절한 조건에서 복층 그래핀의 시뮬레이션 영상들은 육방정계의 대칭성 보다는 삼방정계의 대칭성을 보여 주었다. 이 결과는 복층 그래핀이 3차원 공간에서 [0001] 축 방향 회전에 대해 갖는 삼방정계의 격자 대칭성이 영상에 구현되는 것으로 이해될 수 있다. 단층 그래핀에 대해서는, 관측 위상영상이 삼방정계의 대칭성을 보여주는 현상들이 특히 주목되었다. 이 현상은 그래핀 표면에 전자 밀도의 재 배치에 의한 것으로 설명되었다. 그리고 그래핀의 전자 재 배치를 반영하는, 다만 2번째 Laue 준위 영역의 회절 빔까지만 포함하면 관측 영상과 일치하는 시뮬레이션 위상 영상이 얻어졌다.

Keywords

References

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