Engineering and modifying two-dimensional materials by electron beams
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Introduction Two-dimensional (2D) materials, including graphene, hexagonal boron nitride (h-BN),5,6 phosphorene,7–9 and transitionmetal dichalcogenides (TMDCs)10–12 have been among the most extensively studied materials due to their attractive mechanical, optical, electronic, and chemical properties. Understanding the structure–property relationships in these atomically thin 2D materials requires characterization techniques with atomic resolution and single-atom sensitivity. Aberration-corrected transmission electron microscopy is well suited for such studies. With advances in electron optics and aberration-correction techniques, both conventional transmission electron microscopy (TEM) and scanning TEM (STEM) under low accelerating voltage can now achieve structural analysis at the single-atom level.13–17 Even at low voltages, the energy transferred from the e-beam to 2D materials can be high enough to generate local 1–4
structural distortions or atomic defects18,19 through knock-on damage associated with the ballistic energy transfer from the impinging electron to the recoil atom, electronic excitations, or beam-induced chemical etching. The key challenge is to control the formation and evolution of structural defects during atomic-resolution (S)TEM experiments.5,18,20,21 Notably, structural defects considerably impact material properties and can greatly diversify the physical phenomena in 2D materials. While some defects can deteriorate the mechanical and electronic properties,22 some are known to introduce enhanced catalytic and magnetic characteristics.11,23 Controlling the formation and distribution of specific types of defects using an e-beam with atomic precision provides a powerful approach for structural modification in 2D materials and tuning of properties. This article illustrates how engineering 2D materials using an e-beam with atomic precision, while being challenging, is feasible and promising. The formation of structural defects,
Xiaoxu Zhao, Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore; [email protected] Jani Kotakoski, Faculty of Physics, University of Vienna, Austria; [email protected] Jannik C. Meyer, Faculty of Physics, University of Vienna, Austria; [email protected] Eli Sutter, Department of Mechanical and Materials Engineering, University of Nebraska–Lincoln, USA; [email protected] Peter Sutter, Department of Electrical and Computer Engineering, University of Nebraska–Lincoln, USA; [email protected] Arkady V. Krasheninnikov, Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, Germany; Department of Applied Physics, Aalto University, Finland; [email protected] Ute Kaiser, Central Facility of Electron Microscopy, Ulm University, Germany; [email protected] Wu Zhou, Electron Microscopy Laboratory, School of Physical Sciences, University of Chinese Academy of Sciences, China; [email protected] doi:10.1557/mrs.2017.184
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