title: Edge-Controlled Growth and Etching of Two-Dimensional GaSe Monolayers.
abstract: Understanding the atomistic mechanisms governing the growth of two-dimensional (2D) materials is of great importance in guiding the synthesis of wafer-sized, single-crystalline, high-quality 2D crystals and heterostructures. Etching, in many cases regarded as the reverse process of material growth, has been used to study the growth kinetics of graphene. In this work, we explore a growth-etching-regrowth process of monolayer GaSe crystals, including single-crystalline triangles and irregularly shaped domains formed by merged triangles. We show that the etching begins at a slow rate, creating triangular, truncated triangular, or hexagonally shaped holes that eventually evolve to exclusively triangles that are rotated 60° with respect to the crystalline orientation of the monolayer triangular crystals. The regrowth occurs much faster than etching, reversibly filling the etched holes and then enlarging the size of the monolayer crystals. A theoretical model developed based on kinetic Wulff construction (KWC) theory and density functional theory (DFT) calculations accurately describe the observed morphology evolution of the monolayer GaSe crystals and etched holes during the growth and etching processes, showing that they are governed by the probability of atom attachment/detachment to/from different types of edges with different formation energies of nucleus/dents mediated by chemical potential difference Δμ between Ga and Se. Our growth-etching-regrowth study provides not only guidance to understand the growth mechanisms of 2D binary crystals but also a potential method for the synthesis of large, shape-controllable, high-quality single-crystalline 2D crystals and their lateral heterostructures.
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: Xufan
authors.initials: X
authors.lastname: Li
authors.affiliation: Center for Multidimensional Carbon Materials (CMCM), Institute for Basic Science (IBS) , Ulsan 689-798, Republic of Korea.
authors.forename: Jichen
authors.initials: J
authors.lastname: Dong
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: Juan C
authors.initials: JC
authors.lastname: Idrobo
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Puretzky
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Rouleau
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: David B
authors.initials: DB
authors.lastname: Geohegan
authors.affiliation: Center for Multidimensional Carbon Materials (CMCM), Institute for Basic Science (IBS) , Ulsan 689-798, Republic of Korea.|School of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST) , Ulsan 689-798, Republic of Korea.
authors.forename: Feng
authors.initials: F
authors.lastname: Ding
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: Kai
authors.identifier: 0000-0002-0402-8276
authors.initials: K
authors.lastname: Xiao