title: Atomic Scale Study on Growth and Heteroepitaxy of ZnO Monolayer on Graphene.
abstract: Atomically thin semiconducting oxide on graphene carries a unique combination of wide band gap, high charge carrier mobility, and optical transparency, which can be widely applied for optoelectronics. However, study on the epitaxial formation and properties of oxide monolayer on graphene remains unexplored due to hydrophobic graphene surface and limits of conventional bulk deposition technique. Here, we report atomic scale study of heteroepitaxial growth and relationship of a single-atom-thick ZnO layer on graphene using atomic layer deposition. We demonstrate atom-by-atom growth of zinc and oxygen at the preferential zigzag edge of a ZnO monolayer on graphene through in situ observation. We experimentally determine that the thinnest ZnO monolayer has a wide band gap (up to 4.0 eV), due to quantum confinement and graphene-like structure, and high optical transparency. This study can lead to a new class of atomically thin two-dimensional heterostructures of semiconducting oxides formed by highly controlled epitaxial growth.
authors.affiliation: School of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST) , Ulsan 44919, Republic of Korea.
authors.forename: Hyo-Ki
authors.identifier: 0000-0002-9722-9615
authors.initials: HK
authors.lastname: Hong
authors.affiliation: School of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST) , Ulsan 44919, Republic of Korea.
authors.forename: Junhyeon
authors.initials: J
authors.lastname: Jo
authors.affiliation: School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST) , Ulsan 44919, Republic of Korea.
authors.forename: Daeyeon
authors.initials: D
authors.lastname: Hwang
authors.affiliation: School of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST) , Ulsan 44919, Republic of Korea.
authors.forename: Jongyeong
authors.initials: J
authors.lastname: Lee
authors.affiliation: School of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST) , Ulsan 44919, Republic of Korea.|Center for Multidimensional Carbon Materials, Institute for Basic Science (IBS) , Ulsan 44919, Republic of Korea.
authors.forename: Na Yeon
authors.identifier: 0000-0003-3424-5965
authors.initials: NY
authors.lastname: Kim
authors.affiliation: School of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST) , Ulsan 44919, Republic of Korea.
authors.forename: Seungwoo
authors.initials: S
authors.lastname: Son
authors.affiliation: School of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST) , Ulsan 44919, Republic of Korea.
authors.forename: Jung Hwa
authors.identifier: 0000-0002-2615-963X
authors.initials: JH
authors.lastname: Kim
authors.affiliation: School of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST) , Ulsan 44919, Republic of Korea.
authors.forename: Mi-Jin
authors.initials: MJ
authors.lastname: Jin
authors.affiliation: School of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST) , Ulsan 44919, Republic of Korea.
authors.forename: Young Chul
authors.initials: YC
authors.lastname: Jun
authors.affiliation: Electron Microscopy Center, Empa - Swiss Federal Laboratories for Materials Science and Technology , CH-8600 Dübendorf, Switzerland.
authors.forename: Rolf
authors.initials: R
authors.lastname: Erni
authors.affiliation: School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST) , Ulsan 44919, Republic of Korea.|Center for Multidimensional Carbon Materials, Institute for Basic Science (IBS) , Ulsan 44919, Republic of Korea.
authors.forename: Sang Kyu
authors.identifier: 0000-0002-0332-1534
authors.initials: SK
authors.lastname: Kwak
authors.affiliation: School of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST) , Ulsan 44919, Republic of Korea.|Low Dimensional Carbon Material Center, Ulsan National Institute of Science and Technology (UNIST) , Ulsan 44919, Republic of Korea.
authors.forename: Jung-Woo
authors.identifier: 0000-0001-7038-4001
authors.initials: JW
authors.lastname: Yoo
authors.affiliation: School of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST) , Ulsan 44919, Republic of Korea.|Center for Multidimensional Carbon Materials, Institute for Basic Science (IBS) , Ulsan 44919, Republic of Korea.|Low Dimensional Carbon Material Center, Ulsan National Institute of Science and Technology (UNIST) , Ulsan 44919, Republic of Korea.
authors.forename: Zonghoon
authors.identifier: 0000-0003-3246-4072
authors.initials: Z
authors.lastname: Lee
keywords: 2D materials; Heteroepitaxy; ZnO monolayer; atomically thin; graphene; quantum confinement effect