Single-layer Tungsten Disulfide Mass Production

Graphene is known as the king of materials, but graphene is a zero band gap two-dimensional material, can not be used as transistor channel layer, limiting its further application in nano-electronic devices, photoelectric conversion and other aspects.

Recently, a well-known scholar has published an article on the preparation of monolayer tungsten disulfide with large area and high quality. This method has the advantages of high quality, large size, homogeneity of layers and good controllability, wide growth window, easy operation and enlargement. It can be used as a low-cost and large-scale preparation of monolayer tungsten disulfide with large area. The ideal scheme for single crystal and continuous thin films is as follows:

Using atmospheric pressure chemical vapor deposition technology, using gold as the growth matrix, utilizing the extremely low solubility of gold in tungsten and gold can catalyze the vulcanization of tungsten source, the tungsten source and the sulfur source can be catalyzed on the surface of the gold substrate at high temperature and self-limited growth. Large-size single crystal and large-area continuous film of high quality completely single layer of tungsten disulfide. The tungsten disulfide obtained by the method is completely monolayer, has good uniformity and high quality. The area of the tungsten disulfide depends on the area of the gold matrix used (the area of the tungsten disulfide obtained in the 1 inch diameter reactor can be more than 5 cm² ).

1.A single layer of tungsten disulfide was grown in a horizontal reactor. A quartz tube was used as a reactor. The diameter of the quartz tube was 22 mm. Gas inlets and gas outlets were arranged at both ends of the quartz tube. A quartz boat containing tungsten trioxide powder is placed in the high temperature zone of a horizontal reactor. The gold substrate is placed 1-10 mm above the tungsten trioxide powder. The tungsten trioxide powder is not touched. The thermocouple is located in the high temperature zone of a horizontal reactor to monitor the reaction temperature in real time. Upstream of the quartz tube outside the horizontal reactor is heated by a heater placed outside the quartz tube to produce sulfur vapor.

2.The polycrystalline gold sheets (thickness 100 micron, length * width = 20 mm * 10 mm) were separately washed in acetone, water and ethanol for 30 minutes. After cleaning, the gold sheet is placed in a high temperature furnace and annealed at 1000 ℃ for 10 h, so that the single grain reaches millimeter level. Then, the annealed gold sheet is placed in the central area of the horizontal reactor (22 mm in diameter and 40 mm in length) where a thermocouple monitors the furnace temperature in real time; and heated to 800 ℃ in the atmosphere of argon (500 ml / min in the heating process, 40 ℃ / min in the heating process), and at the hot spot. After heat treatment, the single crystal tungsten disulfide was obtained by starting the heater to 200, starting the growth of tungsten disulfide for 5 hours and slowly cooling to below 300 ℃.

The results of optical microscopy, resonance laser Raman spectroscopy and fluorescence spectroscopy show that the obtained tungsten disulfide is a large single crystal structure. The maximum size is close to 1 mm, the tungsten disulfide structure is continuous and intact, with high quality, and all areas are monolayer. Moreover, the process parameters are stable, and the conditions for realizing low cost continuous production of large area single layer tungsten disulfide are available.

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