Large-area synthesis of high-quality and uniform monolayer WS2 on reusable Au foils.

Yang Gao,Zhibo Liu,Li-Chang Yin,Lian-Mao Peng,Le Huang,Zhiyong Zhang,Teng Ma,Hui-Ming Cheng,Wencai Ren,Dong-Ming Sun,Xiu-Liang Ma,Lai-Peng Ma

doi:10.1038/ncomms9569

Yang Gao, Zhibo Liu + Show 10 more

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https://doi.org/10.1038/ncomms9569

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Abstract

Large-area monolayer WS2 is a desirable material for applications in next-generation electronics and optoelectronics. However, the chemical vapour deposition (CVD) with rigid and inert substrates for large-area sample growth suffers from a non-uniform number of layers, small domain size and many defects, and is not compatible with the fabrication process of flexible devices. Here we report the self-limited catalytic surface growth of uniform monolayer WS2 single crystals of millimetre size and large-area films by ambient-pressure CVD on Au. The weak interaction between the WS2 and Au enables the intact transfer of the monolayers to arbitrary substrates using the electrochemical bubbling method without sacrificing Au. The WS2 shows high crystal quality and optical and electrical properties comparable or superior to mechanically exfoliated samples. We also demonstrate the roll-to-roll/bubbling production of large-area flexible films of uniform monolayer, double-layer WS2 and WS2/graphene heterostructures, and batch fabrication of large-area flexible monolayer WS2 film transistor arrays.

Highlights

Large-area monolayer WS2 is a desirable material for applications in next-generation electronics and optoelectronics
Different from multilayers, monolayer semiconducting transition metal dichalcogenides (TMDCs) have sizable direct bandgaps[1,2,3] and show efficient valley polarization by optical pumping[4,5,6], which opens up the possibility for their use in transistors[7,8,9,10], integrated circuits[11], photodetectors[12], electroluminescent devices[13] and valleytronic and spintronic devices[5,6]
Chemical vapour deposition (CVD) on inert substrates such as SiO2/Si has shown a potential to grow large-area WS2 compared with other methods such as mechanical cleavage[24,25] and liquid exfoliation[3,26]

Summary

Introduction

Large-area monolayer WS2 is a desirable material for applications in next-generation electronics and optoelectronics. The chemical vapour deposition (CVD) with rigid and inert substrates for large-area sample growth suffers from a non-uniform number of layers, small domain size and many defects, and is not compatible with the fabrication process of flexible devices. In addition to conventional rigid device applications, transparent and flexible electronic and optoelectronic devices have been widely considered to be one of the most appealing applications of all 2D materials because of their high transparency and good flexibility[1,16] To this end, the low-cost fabrication of large-area monolayer WS2 films on flexible substrates is highly desired. For CVD-grown 2D WS2 materials on inert substrates, the growth substrates usually have to be etched away by acidic or basic solutions such as concentrated HF, KOH and NaOH before they are transferred to flexible substrates[7,18,19,20,21]

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Conclusion