title: Scalable Production of a Few-Layer MoS2/WS2 Vertical Heterojunction Array and Its Application for Photodetectors.
abstract: Vertical heterojunctions of two two-dimensional (2D) transition metal dichalcogenides (TMDs) have attracted considerable attention recently. A variety of heterojunctions can be constructed by stacking different TMDs to form fundamental building blocks in different optoelectronic devices such as photodetectors, solar cells, and light-emitting diodes. However, these applications are significantly hampered by the challenges of large-scale production of van der Waals stacks of atomically thin materials. Here, we demonstrate scalable production of periodic patterns of few-layer WS2, MoS2, and their vertical heterojunction arrays by a thermal reduction sulfurization process. In this method, a two-step chemical vapor deposition approach was developed to effectively prevent the phase mixing of TMDs in an unpredicted manner, thus affording a well-defined interface between WS2 and MoS2 in the vertical dimension. As a result, large-scale, periodic arrays of few-layer WS2, MoS2, and their vertical heterojunctions can be produced with desired size and density. Photodetectors based on the as-produced MoS2/WS2 vertical heterojunction arrays were fabricated, and a high photoresponsivity of 2.3 A·W(-1) at an excitation wavelength of 450 nm was demonstrated. Flexible photodetector devices using MoS2/WS2 heterojunction arrays were also demonstrated with reasonable signal/noise ratio. The approach in this work is also applicable to other TMD materials and can open up the possibilities of producing a variety of vertical van der Waals heterojunctions in a large scale toward optoelectronic applications.
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, People's Republic of China.|Department of Materials Science and Engineering, Monash University , Clayton, Victoria 3800, Australia.
authors.forename: Yunzhou
authors.initials: Y
authors.lastname: Xue
authors.affiliation: Department of Materials Science and Engineering, Monash University , Clayton, Victoria 3800, Australia.
authors.forename: Yupeng
authors.initials: Y
authors.lastname: Zhang
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, People's Republic of China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Beijing National Laboratory for Molecular Sciences Institute of Chemistry, Chinese Academy of Sciences , Beijing 100190, People's Republic of China.
authors.forename: Hongtao
authors.initials: H
authors.lastname: Liu
authors.affiliation: Department of Materials Science and Engineering, Monash University , Clayton, Victoria 3800, Australia.
authors.forename: Jingchao
authors.initials: J
authors.lastname: Song
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, People's Republic of China.
authors.forename: Joice
authors.initials: J
authors.lastname: Sophia
authors.affiliation: Department of Materials Science and Engineering, Monash University , Clayton, Victoria 3800, Australia.
authors.forename: Jingying
authors.initials: J
authors.lastname: Liu
authors.affiliation: Department of Materials Science and Engineering, Monash University , Clayton, Victoria 3800, Australia.
authors.forename: Zaiquan
authors.initials: Z
authors.lastname: Xu
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, People's Republic of China.
authors.forename: Qingyang
authors.initials: Q
authors.lastname: Xu
authors.affiliation: Department of Materials Science and Engineering, Monash University , Clayton, Victoria 3800, Australia.
authors.forename: Ziyu
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Department of Materials Science and Engineering, Monash University , Clayton, Victoria 3800, Australia.
authors.forename: Jialu
authors.initials: J
authors.lastname: Zheng
authors.affiliation: Beijing National Laboratory for Molecular Sciences Institute of Chemistry, Chinese Academy of Sciences , Beijing 100190, People's Republic of China.
authors.forename: Yunqi
authors.initials: Y
authors.lastname: Liu
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, People's Republic of China.
authors.forename: Shaojuan
authors.initials: S
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, People's Republic of China.|Department of Materials Science and Engineering, Monash University , Clayton, Victoria 3800, Australia.
authors.forename: Qiaoliang
authors.initials: Q
authors.lastname: Bao
keywords: flexible device; molybdenum disulfide; photodetector; tungsten disulfide; vertical heterojunction