title: Synthesis and Transfer of Large-Area Monolayer WS2 Crystals: Moving Toward the Recyclable Use of Sapphire Substrates.
abstract: Two-dimensional layered transition metal dichalcogenides (TMDs) show intriguing potential for optoelectronic devices due to their exotic electronic and optical properties. Only a few efforts have been dedicated to large-area growth of TMDs. Practical applications will require improving the efficiency and reducing the cost of production, through (1) new growth methods to produce large size TMD monolayer with less-stringent conditions, and (2) nondestructive transfer techniques that enable multiple reuse of growth substrate. In this work, we report to employ atmospheric pressure chemical vapor deposition (APCVD) for the synthesis of large size (>100 μm) single crystals of atomically thin tungsten disulfide (WS2), a member of TMD family, on sapphire substrate. More importantly, we demonstrate a polystyrene (PS) mediated delamination process via capillary force in water which reduces the etching time in base solution and imposes only minor damage to the sapphire substrate. The transferred WS2 flakes are of excellent continuity and exhibit comparable electron mobility after several growth cycles on the reused sapphire substrate. Interestingly, the photoluminescence emission from WS2 grown on the recycled sapphire is much higher than that on fresh sapphire, possibly due to p-type doping of monolayer WS2 flakes by a thin layer of water intercalated at the atomic steps of the recycled sapphire substrate. The growth and transfer techniques described here are expected to be applicable to other atomically thin TMD materials.
authors.affiliation: †Department of Materials Science and Engineering, Faculty of Engineering, Monash University, Clayton 3800, Victoria, Australia.|‡The Melbourne Centre for Nanofabrication, 151 Wellington Road, Clayton 3168, Victoria, Australia.
authors.forename: Zai-Quan
authors.initials: ZQ
authors.lastname: Xu
authors.affiliation: †Department of Materials Science and Engineering, Faculty of Engineering, Monash University, Clayton 3800, Victoria, Australia.
authors.forename: Yupeng
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: †Department of Materials Science and Engineering, Faculty of Engineering, Monash University, Clayton 3800, Victoria, Australia.|§Institute of Functional Nano and Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, and Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215123, P. R. China.
authors.forename: Shenghuang
authors.initials: S
authors.lastname: Lin
authors.affiliation: ⊥Department of Civil Engineering, Monash University, Clayton 3800, Victoria, Australia.|∥School of Physics, Monash University, Monash 3800, Victoria, Australia.
authors.forename: Changxi
authors.initials: C
authors.lastname: Zheng
authors.affiliation: †Department of Materials Science and Engineering, Faculty of Engineering, Monash University, Clayton 3800, Victoria, Australia.
authors.forename: Yu Lin
authors.initials: YL
authors.lastname: Zhong
authors.affiliation: †Department of Materials Science and Engineering, Faculty of Engineering, Monash University, Clayton 3800, Victoria, Australia.
authors.forename: Xue
authors.initials: X
authors.lastname: Xia
authors.affiliation: †Department of Materials Science and Engineering, Faculty of Engineering, Monash University, Clayton 3800, Victoria, Australia.
authors.forename: Zhipeng
authors.initials: Z
authors.lastname: Li
authors.affiliation: §Institute of Functional Nano and Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, and Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215123, P. R. China.
authors.forename: Ponraj Joice
authors.initials: PJ
authors.lastname: Sophia
authors.affiliation: ∥School of Physics, Monash University, Monash 3800, Victoria, Australia.
authors.forename: Michael S
authors.initials: MS
authors.lastname: Fuhrer
authors.affiliation: †Department of Materials Science and Engineering, Faculty of Engineering, Monash University, Clayton 3800, Victoria, Australia.
authors.forename: Yi-Bing
authors.initials: YB
authors.lastname: Cheng
authors.affiliation: †Department of Materials Science and Engineering, Faculty of Engineering, Monash University, Clayton 3800, Victoria, Australia.|§Institute of Functional Nano and Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, and Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215123, P. R. China.
authors.forename: Qiaoliang
authors.initials: Q
authors.lastname: Bao
keywords: atmospheric pressure chemical vapor deposition (APCVD); monolayer; recyclability; transfer; transition metal dichalcogenide