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Researchers obtain atomically thin molybdenum disulfide films on large-area substrate

wallpapers News 2020-10-10
Unlike graphene, the bandgap's optimal width in molybdenum disulfide (MoS2) makes it suitable for use in electronic devices. Each MOS2 layer has a sandwich structure, and the molybdenum layer is squeezed between two layers of sulfur atoms. Two-dimensional van der Waals heterostructures combined with different two-dimensional materials, also showed great promise. They have been widely used in energy-related applications and catalysis. Wafer-level (large area) 2-D molybdenum disulfide synthesis shows the potential for breakthroughs in the creation of transparent and flexible electronic devices, optical communications for next-generation computers, and other fields of electronics and optoelectronics.
Scientists proposed method2 of synthesizing MoS, including two steps: First, the MoO thin film three is made using atomic layer deposition technology, which provides precise nuclear layer thickness and allows the growth of conformal coatings on all surfaces. MoO3 can quickly obtain sulfur dioxide on a wafer with a diameter of up to 300 mm, and then heat the film in sulfur vapor. As a result, the oxygen atoms in MoO3 are replaced by sulfur atoms to form MoS2. It is possible to grow atomically thin MoS 2 films on areas up to tens of square centimeters.

The researchers determined that the structure of the film depends on the curing temperature. The film vulcanized at 500°C contains grains, each buried in an amorphous matrix, and each grain is only a few nanometers. At 700°C, the crystallites' width is about 10-20 nm, and the S-Mo-S layer is oriented perpendicular to the surface. As a result, the body has many dangling bonds. This structure shows high catalytic activity in many reactions, including hydrogen release reactions. For MoS 2 to be used in electronic devices, the S-Mo-S layer must be parallel to the surface, achieved at a vulcanization temperature of 900-1,000°C. The resulting film is as thin as 1.3 nm or two molecular layers and has a commercially significant (i.e., sufficiently large) area.

The MoS 2 film synthesized under optimal conditions was introduced into a metal-dielectric-semiconductor prototype structure based on ferroelectric oxide and simulated field-effect transistor. The MoS 2 film in these structures serves as a semiconductor channel. By switching the polarization direction of the ferroelectric layer to control its conductivity. When in contact with MoS 2, La: (HfO 2 -ZrO 2) material was developed earlier in the MIPT laboratory, and its residual polarization was found to be about 18 micro coulombs per square centimeter. The switch endurance of 5 million cycles broke the world record of 100,000 cycles of silicon channel.
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