Discovery and Development of Molybdenum Disulfide
Although graphene has many dazzling advantages, it also has disadvantages, especially its inability to act as a semiconductor-which is the cornerstone of microelectronics. Chemists and materials scientists are trying to get past graphene and find other materials. They are synthesizing two other two-dimensional flake materials that have both flexibility and transparency, and have electronic properties that graphene cannot match. Molybdenum disulfide is one of them.
Molybdenum disulfide was synthesized in 2008 and is a member of a large family of transition metal disulfide materials (TMDs). This somewhat "fancy" name represents their structure: a transition metal atom (i.e. molybdenum atom) and a pair of atoms from column 16 of the periodic table including sulfur and selenium (the element family is based on oxygen). Famous for group elements).
To the surprise of electronics manufacturers, all TMDs are semiconductors. They are almost the same thinness as graphene (in molybdenum disulfide, two layers of sulfur atoms sandwich a layer of molybdenum atoms like a "sandwich"), but they have other advantages. As far as molybdenum disulfide is concerned, one of the advantages is the speed at which electrons travel in the flat sheet, that is, the electron mobility. The electron migration rate of molybdenum disulfide is about 100 cm2/vs (that is, 100 electrons per square centimeter per volt second), which is much lower than the electron migration rate of crystalline silicon of 1400 cm2/vs but is thinner than amorphous silicon and others The migration speed of semiconductors is better, and scientists are studying these materials for use in future electronic products, such as flexible display screens and other electronic products that can be flexibly stretched.
Studies have shown that molybdenum disulfide is also extremely easy to make, even for large pieces of two-dimensional materials. This allows engineers to test their performance in electronic products at a very fast speed. For example, in 2011, a research team led by Andras Kis of the Swiss Federal Institute of Technology published an article in "Nature-Nanotechnology" that they used a single layer of molybdenum disulfide thin-film of only 0.65 nanometers to make the first transistors. It turns out that those products and subsequent products have other unique attributes than similar silicon-based products that are more technologically advanced.
In addition, molybdenum disulfide has other desirable properties, namely the direct bandgap, which allows the material to convert electrons into photons and vice versa. This feature also makes molybdenum disulfide a good candidate for use in optical devices, such as light emitters, lasers, photodetectors, and even solar cells. Some scientists said that this material also has the characteristics of abundant reserves, low price, non-toxicity, etc. Therefore, Yi-Hsien Lee believes: "It has a bright future."
However, Tomanek believes that the electron migration rate of molybdenum disulfide is still not high enough to have a competitive advantage in the crowded electronics market. The reason is the structural characteristics of this material. When electrons move inside it, they will bounce off the structure when they encounter larger metal atoms, thereby reducing the migration speed.
But some scientists said that this "stumbling block" will be short-lived. Researchers are trying to circumvent these obstacles by making a slightly thicker multilayer molybdenum disulfide sheet, thereby providing a path for compressed electrons to bypass the roadblock.
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