Unusual role of epilayer-substrate interactions in determining orientational relations in van der Waals epitaxy.
Using selected-area low-energy electron diffraction analysis, we showed strict orientational alignment of monolayer hexagonal boron nitride (h-BN) crystallites with Cu(100) surface lattices of Cu foil substrates during atmospheric pressure chemical vapor deposition. In sharp contrast, the graphene-Cu(100) system is well-known to assume a wide range of rotations despite graphene's crystallographic similarity to h-BN. Our density functional theory calculations uncovered the origin of this surprising difference: The crystallite orientation is determined during nucleation by interactions between the cluster's edges and the substrate. Unlike the weaker B- and N-Cu interactions, strong C-Cu interactions rearrange surface Cu atoms, resulting in the aligned geometry not being a distinct minimum in total energy. The discovery made in this specific case runs counter to the conventional wisdom that strong epilayer-substrate interactions enhance orientational alignment in epitaxy and sheds light on the factors that determine orientational relation in van der Waals epitaxy of 2D materials.
Department of Electrical Engineering and Computer Science, University of Tennessee, Knoxville, TN 37996;
Lei
L
Liu
Materials Physics Department, Sandia National Laboratories, Livermore, CA 94550;
David A
DA
Siegel
International Center for Quantum Design of Functional Materials, Hefei National Laboratory for Physical Sciences at the Microscale, and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China; Department of Physics, The University of Tennessee, Knoxville, TN 37996;
Wei
W
Chen
Department of Electrical Engineering and Computer Science, University of Tennessee, Knoxville, TN 37996; Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996;
Peizhi
P
Liu
Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996; Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831;
Junjie
J
Guo
Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996; Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831;
Gerd
G
Duscher
International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China; and Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
Chong
C
Zhao
International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China; and Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
Hao
H
Wang
Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
Wenlong
W
Wang
Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
Xuedong
X
Bai
Materials Physics Department, Sandia National Laboratories, Livermore, CA 94550;
Kevin F
KF
McCarty
International Center for Quantum Design of Functional Materials, Hefei National Laboratory for Physical Sciences at the Microscale, and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China; zhangzy@ustc.edu.cn ggu1@utk.edu.
Zhenyu
Z
Zhang
Department of Electrical Engineering and Computer Science, University of Tennessee, Knoxville, TN 37996; zhangzy@ustc.edu.cn ggu1@utk.edu.
Gong
G
Gu
graphene; hexagonal boron nitride; orientational relation; two-dimensional materials; van der Waals epitaxy