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(a) Structure of a hexagonal TMD monolayer. M atoms are in black and X atoms are in yellow. (b) A hexagonal TMD monolayer seen from above. Transition-metal dichalcogenide (TMD or TMDC) monolayers are atomically thin semiconductors of the type MX 2, with M a transition-metal atom (Mo, W, etc.) and X a chalcogen atom (S, Se, or Te).
MoS 2, the most common metal dichalcogenide, adopts a layered structure. Metal dichalcogenides have the formula ME 2, where M = a transition metal and E = S, Se, Te. [7] The most important members are the sulfides. They are always dark diamagnetic solids, insoluble in all solvents, and exhibit semiconducting properties. Some are superconductors ...
The oxidation of other semiconductor transition metal dichalcogenides (S-TMDs) such as MoS 2, has similarly been observed to occur in ambient light and atmospheric conditions. [9] WS 2 is also attacked by a mixture of nitric and hydrofluoric acid. When heated in oxygen-containing atmosphere, WS 2 converts to tungsten trioxide.
The compound is classified as a transition metal dichalcogenide. It is a silvery black solid that occurs as the mineral molybdenite, the principal ore for molybdenum. [6] MoS 2 is relatively unreactive. It is unaffected by dilute acids and oxygen. In appearance and feel, molybdenum disulfide is similar to graphite.
The transition from α- to β-MoTe 2 happens at 820 °C, but if Te is reduced by 5% the required transition temperature increases to 880 °C. [25] K. Ueno and K. Fukushima claim that when the α form is heated in a low or high vacuum that it oxidises to form MoO 2 and that reversible phase transitions do not take place.
Compounds of this category are known as transition metal dichalcogenides, abbreviated TMDCs. These compounds, as the name suggests, are made up of a transition metals and elements of group 16 on the periodic table of the elements. Compared to MoS 2, MoSe 2 exhibits higher electrical conductivity. [7]
NbSe 2 crystallizes in several related forms, and can be mechanically exfoliated into monatomic layers, similar to other transition metal dichalcogenide monolayers. Monolayer NbSe 2 exhibits very different properties from the bulk material, such as of Ising superconductivity, quantum metallic state, and strong enhancement of the CDW. [3]
Nanoparticle monolayers can be used to create functional surfaces that have for instance anti-reflective or superhydrophobic properties. [2] [3] Monolayers are frequently encountered in biology. A micelle is a monolayer, and the phospholipid lipid bilayer structure of biological membranes is technically two monolayers. Langmuir monolayers are ...