title: Synthesis of aligned symmetrical multifaceted monolayer hexagonal boron nitride single crystals on resolidified copper.
abstract: Atomically smooth hexagonal boron nitride (h-BN) films are considered as a nearly ideal dielectric interface for two-dimensional (2D) heterostructure devices. Reported mono- to few-layer 2D h-BN films, however, are mostly small grain-sized, polycrystalline and randomly oriented. Here we report the growth of centimetre-sized atomically thin h-BN films composed of aligned domains on resolidified Cu. The films consist of monolayer single crystalline triangular and hexagonal domains with size of up to ∼10 μm. The domains converge to symmetrical multifaceted shapes such as "butterfly" and "6-apex-star" and exhibit ∼75% grain alignment for over millimetre distances as verified through transmission electron microscopy. Scanning electron microscopy images reveal that these domains are aligned for over centimetre distances. Defect lines are generated along the grain boundaries of mirroring h-BN domains due to the two different polarities (BN and NB) and edges with the same termination. The observed triangular domains with truncated edges and alternatively hexagonal domains are in accordance with Wulff shapes that have minimum edge energy. This work provides an extensive study on the aligned growth of h-BN single crystals over large distances and highlights the obstacles that are needed to be overcome for a 2D material with a binary configuration.
authors.affiliation: School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore. htteo@ntu.edu.sg and Temasek Laboratories@NTU, 50 Nanyang Avenue, Singapore 639798, Singapore.
authors.forename: Roland Yingjie
authors.initials: RY
authors.lastname: Tay
authors.affiliation: School of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, Republic of Korea.
authors.forename: Hyo Ju
authors.initials: HJ
authors.lastname: Park
authors.affiliation: School of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, Republic of Korea.
authors.forename: Gyeong Hee
authors.initials: GH
authors.lastname: Ryu
authors.affiliation: School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore. htteo@ntu.edu.sg and CNRS-International NTU Thales Research Alliance CINTRA UMI 3288, Research Techno Plaza, 50 Nanyang Drive, Singapore 637553, Singapore.
authors.forename: Dunlin
authors.initials: D
authors.lastname: Tan
authors.affiliation: Temasek Laboratories@NTU, 50 Nanyang Avenue, Singapore 639798, Singapore.
authors.forename: Siu Hon
authors.initials: SH
authors.lastname: Tsang
authors.affiliation: School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore. htteo@ntu.edu.sg and CNRS-International NTU Thales Research Alliance CINTRA UMI 3288, Research Techno Plaza, 50 Nanyang Drive, Singapore 637553, Singapore.
authors.forename: Hongling
authors.initials: H
authors.lastname: Li
authors.affiliation: School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore. htteo@ntu.edu.sg.
authors.forename: Wenwen
authors.initials: W
authors.lastname: Liu
authors.affiliation: School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore. htteo@ntu.edu.sg and School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore.
authors.forename: Edwin Hang Tong
authors.initials: EH
authors.lastname: Teo
authors.affiliation: School of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, Republic of Korea and Center for Multidimensional Carbon Materials, Institute for Basic Science (IBS), Ulsan 689-798, Republic of Korea.
authors.forename: Zonghoon
authors.initials: Z
authors.lastname: Lee
authors.affiliation: Department of Materials Science and Engineering, Technion, Israel Institute of Technology, Haifa 3200003, Israel.
authors.forename: Yeshayahu
authors.initials: Y
authors.lastname: Lifshitz
authors.affiliation: Center for Multidimensional Carbon Materials, Institute for Basic Science (IBS), Ulsan 689-798, Republic of Korea and Department of Chemistry, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, Republic of Korea.
authors.forename: Rodney S
authors.initials: RS
authors.lastname: Ruoff