Recently, Ren Wencai, a researcher at the Advanced Carbon Materials Research Department of the National Institute of Materials Science, Institute of Materials Science, Chinese Academy of Sciences, has made new progress in the preparation of large-area high-quality uniform single-layer WS2 and flexible electronics applications. Based on binary phase diagram analysis and theoretical calculations, they found that gold is the only metal that does not react with sulfur at high temperatures to form sulfides, and gold has catalytic activity, which can effectively reduce the barrier of tungsten trisulfide vulcanization process, and gold at high temperature. The solubility of the tungsten atom is extremely low. On this basis, they proposed a surface-catalyzed atmospheric pressure CVD method using gold as a growth substrate to realize the preparation of high-quality, uniform single-layer millimeter-sized WS2 single crystals and large-area films. It is found that, similar to the growth of graphene on copper, the catalytic activity of gold and the extremely low solubility of tungsten in gold make the growth of WS2 on gold follow the self-limiting surface catalytic growth mechanism, thus ensuring a uniform single layer of high quality WS2 crystal. Growth. In addition, the single-layer WS2 prepared under normal pressure is weakly bonded to the gold matrix, so the electrochemical bubbling method can be used to achieve high-quality transfer of WS2 without damaging the gold matrix. The single layer WS2 produced by this method has a high crystalline quality and exhibits optical and electrical properties comparable to those prepared by mechanical stripping (far better than materials grown by inert matrix CVD).

In addition, they use the characteristics of gold foil with good flexibility and chemical stability, and propose a non-destructive transfer method combining roll-to-roll and electrochemical bubbling to realize large-area single-layer WS2 film without destroying the gold matrix. Low cost continuous transfer to flexible transparent substrates such as PET, PEN, etc. Through the layer transfer, a large-area flexible transparent double-layer, multi-layer WS2 film and a WS2/graphene laminated heterostructure functional film can also be prepared. Using the roll-to-roll electrochemical bubbling lossless transfer method, they also realized the fabrication of a large-area flexible transparent single-layer WS2 thin film transistor array. The electrical properties of the flexible device are comparable to those of the SiO2/Si substrate and are bent. After 100 times, the electrical performance does not decay.
The low-cost, large-area preparation of high-quality uniform single-layer WS2 single crystals and thin films lays the material foundation for their applications in flexible electronic/optoelectronic devices and valley electron and spintronic devices. The results were funded by the National Natural Science Foundation of China's Outstanding Youth Fund, major projects, innovation groups, and key deployment projects of the Chinese Academy of Sciences. They were published online on October 9th in Nature Communications (Nature Communications, 6:8569, DOI: 10.1038/ Ncomms9569, 2015).