Top-view atomic images of MoSe2 before and after (right) ion irradiation
[1]
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Names | |
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IUPAC name
bis(selanylidene)molybdenum
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Other names
molybdenum diselenide, molybdenumdiselenide, molybdenum selenide, diselanylidenemolybdenum, molybdenum(IV) selenide
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Identifiers | |
3D model (
JSmol)
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ECHA InfoCard | 100.031.831 |
PubChem
CID
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CompTox Dashboard (
EPA)
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Properties | |
MoSe 2 | |
Molar mass | 253.86 g/mol [2] |
Appearance | crystalline solid |
Density | 6.90 g/cm3 [2] |
Melting point | >1200 °C [2] |
Band gap | ~0.85 eV (indirect, bulk) ~1.5 eV (direct, monolayer) [3] [4] |
Structure | |
hP6,
space group P6 3/mmc, No 194 [5] | |
a = 0.3283 nm, c = 1.2918 nm
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Trigonal prismatic (MoIV) Pyramidal (Se2−) | |
Related compounds | |
Other
anions
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Molybdenum dioxide Molybdenum disulfide Molybdenum ditelluride Tantalum diselenide |
Other
cations
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Tungsten diselenide |
Except where otherwise noted, data are given for materials in their
standard state (at 25 °C [77 °F], 100 kPa).
|
Molybdenum diselenide (MoSe
2) is an
inorganic compound of
molybdenum and
selenium. Its structure is similar to that of
MoS
2.
[6] 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]
Like many TMDCs, MoSe
2 is a layered material with strong in-plane bonding and weak out-of-plane interactions. These interactions lead to exfoliation into two-dimensional layers of single unit cell thickness.
[8]
The most common form of these TMDCs have trilayers of
molybdenum sandwiched between
selenium ions causing a
trigonal prismatic metal bonding coordination, but it is
octahedral when the compound is
exfoliated. The metal ion in these compounds is surrounded by six Se2−
ions. The coordination geometry of the Mo is sometimes found as octahedral and trigonal prismatic.
[9]
Synthesis of MoSe
2 involves direct reaction of molybdenum and selenium in a sealed tube at high temperature.
Chemical vapor transport with a
halogen (usually
bromine or
iodine) is used to purify the compound at very low pressure (less than 10-6 torr) and very high temperature (600–700 °C). It has to be heated very gradually to prevent explosion due to its strong
exothermic reaction.
Stoichiometric layers crystallize in a hexagonal structure as the sample cools.
[9] Excess selenium can be removed by sublimation under vacuum.
[10] The synthesis reaction of MoSe
2 is:
Single-crystal-thick layers of MoSe
2 are produced by
scotch tape exfoliation from bulk crystals or by
chemical vapor deposition (CVD).
[11]
[12]
The
electron mobility of 2D-MoSe
2 is significantly higher than that of 2D-MoS
2. 2D MoSe
2 adopts structures reminiscent of
graphene, although the latter's electron mobility is thousands of times greater still. In contrast to graphene, 2D-MoSe
2 has a
direct
band gap, suggesting applications in
transistors and
photodetectors.
[11]
Molybdenum(IV) selenide occurs in the nature as the extremely rare mineral drysdallite. [13]