title: Evaporative thinning: a facile synthesis method for high quality ultrathin layers of 2D crystals.
abstract: The palette of two-dimensional materials has expanded beyond graphene in recent years to include the chalcogenides among other systems. However, there is a considerable paucity of methods for controlled synthesis of mono- and/or few-layer two-dimensional materials with desirable quality, reproducibility, and generality. Here we show a facile top-down synthesis approach for ultrathin layers of 2D materials down to monolayer. Our method is based on controlled evaporative thinning of initially large sheets, as deposited by vapor mass-transport. Rather than optimizing conditions for monolayer deposition, our approach makes use of selective evaporation of thick sheets to control the eventual thickness, down to a monolayer, a process which appears to be self-stopping. As a result, 2D sheets with high yield, high reproducibility, and excellent quality can be generated with large (>10 μm) and thin (∼ 1-2 nm) dimensions. Evaporative thinning promises to greatly reduce the difficulty involved in isolating large, mono- and few-layers of 2D materials for subsequent studies.
authors.affiliation: Department of Materials Science and Engineering, ‡Department of Electrical Engineering and Computer Science, §Department of Applied Physics, and ∥Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States.
authors.forename: Yi-Kai
authors.initials: YK
authors.lastname: Huang
authors.forename: Jeffrey D
authors.initials: JD
authors.lastname: Cain
authors.forename: Lintao
authors.initials: L
authors.lastname: Peng
authors.forename: Shiqiang
authors.initials: S
authors.lastname: Hao
authors.forename: Thomas
authors.initials: T
authors.lastname: Chasapis
authors.forename: Mercouri G
authors.initials: MG
authors.lastname: Kanatzidis
authors.forename: Christopher
authors.initials: C
authors.lastname: Wolverton
authors.forename: Matthew
authors.initials: M
authors.lastname: Grayson
authors.forename: Vinayak P
authors.initials: VP
authors.lastname: Dravid
keywords: 2D synthesis; bismuth selenide; transmission electron microscopy; two-dimensional (2D) materials