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Nano Lett. 2018 Mar 14;18(3):2016-2020. doi: 10.1021/acs.nanolett.7b05457. Epub 2018 Feb 6.

Electron-Beam-Induced Synthesis of Hexagonal 1 H-MoSe2 from Square β-FeSe Decorated with Mo Adatoms.

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Department of Physics and Astronomy , Vanderbilt University , Nashville , Tennessee 37235 , United States.
Materials Science and Technology Division , Oak Ridge National Laboratory , Oak Ridge , Tennessee 37831 , United States.
National Institute of Advanced Industrial Science and Technology (AIST) , AIST Central 5 , Tsukuba 305-8565 , Japan.
Center for Programmable Materials, School of Materials Science and Engineering , Nanyang Technological University , 639798 Singapore.
Centre for Micro-/Nano-electronics (NOVITAS), School of Electrical & Electronic Engineering , Nanyang Technological University , 50 Nanyang Avenue , 639798 Singapore.
CINTRA CNRS/NTU/THALES, UMI 3288, Research Techno Plaza , 50 Nanyang Drive, Border X Block, Level 6 , 637553 Singapore.
Department of Electrical Engineering and Computer Science , Vanderbilt University , Nashville , Tennessee 37235 , United States.
Department of Mechanical Engineering , The University of Tokyo , Tokyo 113-8656 , Japan.


Two-dimensional (2D) materials have generated interest in the scientific community because of the advanced electronic applications they might offer. Powerful electron beam microscopes have been used not only to evaluate the structures of these materials but also to manipulate them by forming vacancies, nanofragments, and nanowires or joining nanoislands together. In this work, we show that the electron beam in a scanning transmission electron microscope (STEM) can be used in yet another way: to mediate the synthesis of 2D 1 H-MoSe2 from Mo-decorated 2D β-FeSe and simultaneously image the process on the atomic scale. This is quite remarkable given the different crystal structures of the reactant (square lattice β-FeSe) and the product (hexagonal lattice 1 H-MoSe2). The feasibility of the transformation was first explored by theoretical calculations that predicted that the reaction is exothermic. Furthermore, a theoretical reaction path to forming a stable 1 H-MoSe2 nucleation kernel within pure β-FeSe was found, demonstrating that the pertinent energy barriers are smaller than the energy supplied by the STEM electron beam.


DFT; FeSe; MoSe2; STEM; electron beam; synthesis

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