Chemistry:Molybdenum diselenide

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Molybdenum diselenide
Molybdenum diselenide
MoSe2 STEM.jpg
Top-view atomic images of MoSe2 before and after (right) ion irradiation[1]
Names
IUPAC name
bis(selanylidene)molybdenum
Other names
molybdenum diselenide, molybdenumdiselenide, molybdenum selenide, diselanylidenemolybdenum, molybdenum(IV) selenide
Identifiers
3D model (JSmol)
Properties
MoSe2
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 P63/mmc, No 194[5]
a = 0.3283 nm, c = 1.2918 nm
Trigonal prismatic (MoIV)
Pyramidal (Se2−)
Related compounds
Other anions
 Molybdenum dioxide
Molybdenum disulfide
Molybdenum ditelluride
Tantalum diselenide
Other cations
 Tungsten diselenide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references
Tracking categories (test):

Molybdenum diselenide (MoSe2) is an inorganic compound of molybdenum and selenium. Its structure is similar to that of MoS2.[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 MoS2, MoSe2 exhibits higher electrical conductivity.[7]

Structure

Like many TMDCs, MoSe2 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

Synthesis of MoSe2 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 MoSe2 is:

Mo + 2 Se → MoSe2

2D-MoSe2

Single-crystal-thick layers of MoSe2 are produced by scotch tape exfoliation from bulk crystals or by chemical vapor deposition (CVD).[11][12]

The electron mobility of 2D-MoSe2 is significantly higher than that of 2D-MoS2. 2D MoSe2 adopts structures reminiscent of graphene, although the latter's electron mobility is thousands of times greater still. In contrast to graphene, 2D-MoSe2 has a direct band gap, suggesting applications in transistors and photodetectors.[11]

Natural occurrence

Molybdenum(IV) selenide occurs in the nature as the extremely rare mineral drysdallite.[13]

References

  1. ↑ Iberi, Vighter; Liang, Liangbo; Ievlev, Anton V.; Stanford, Michael G.; Lin, Ming-Wei; Li, Xufan; Mahjouri-Samani, Masoud; Jesse, Stephen et al. (2016). "Nanoforging Single Layer MoSe2 Through Defect Engineering with Focused Helium Ion Beams". Scientific Reports 6: 30481. doi:10.1038/srep30481. PMID 27480346. Bibcode: 2016NatSR...630481I. 
  2. ↑ 2.0 2.1 2.2 Haynes, William M., ed (2011). CRC Handbook of Chemistry and Physics (92nd ed.). Boca Raton, FL: CRC Press. p. 4.76. ISBN 1439855110. 
  3. ↑ Yun, Won Seok; Han, S. W.; Hong, Soon Cheol; Kim, In Gee; Lee, J. D. (2012). "Thickness and strain effects on electronic structures of transition metal dichalcogenides: 2H-MX2 semiconductors (M = Mo, W; X = S, Se, Te)". Physical Review B 85 (3): 033305. doi:10.1103/PhysRevB.85.033305. Bibcode: 2012PhRvB..85c3305Y. 
  4. ↑ Kioseoglou, G.; Hanbicki, A. T.; Currie, M.; Friedman, A. L.; Jonker, B. T. (2016). "Optical polarization and intervalley scattering in single layers of MoS2 and MoSe2". Scientific Reports 6: 25041. doi:10.1038/srep25041. PMID 27112195. Bibcode: 2016NatSR...625041K. 
  5. ↑ Agarwal, M. K.; Patel, P. D.; Joshi, R. M. (1986). "Growth conditions and structural characterization of MoSexTe2−x (0 ⩽ x ⩽ 2) single crystals". Journal of Materials Science Letters 5: 66–68. doi:10.1007/BF01671439. 
  6. ↑ Greenwood, N. N.; Earnshaw, A. (11 November 1997). Chemistry of the Elements. Elsevier. pp. 1017–1018. ISBN 978-0-08-050109-3. https://books.google.com/books?id=EvTI-ouH3SsC. 
  7. ↑ Eftekhari, Ali (2017). "Molybdenum Diselenide (MoSe2) for Energy Storage, Catalysis, and Optoelectronics". Applied Materials Today 8: 1–16. doi:10.1016/j.apmt.2017.01.006. 
  8. ↑ Wang, Qing Hua; Kalantar-Zadeh, Kourosh; Kis, Andras; Coleman, Jonathan N.; Strano, Michael S. (2012). "Electronics and optoelectronics of two-dimensional transition metal dichalcogenides". Nature Nanotechnology 7 (11): 699–712. doi:10.1038/nnano.2012.193. PMID 23132225. Bibcode: 2012NatNa...7..699W. http://infoscience.epfl.ch/record/182177. 
  9. ↑ 9.0 9.1 Parilla, P.; Dillon, A.; Parkinson, B.; Jones, K.; Alleman, J.; Riker, G.; Ginley, D.; Heben, M; Formation of Nanooctahedra in Molybdenum Disulfide and Molybdenum Diselenide Using Pulsed Vapor Transport doi:10.1021/jp036202
  10. ↑ Al-hilli, A.; Evans, L. The Preparation and Properties of Transition Metal Dichalcogenide Single Crystals. Journal of Crystal Growth. 1972. 15, 93–101. doi:10.1016/0022-0248(72)90129-7
  11. ↑ 11.0 11.1 "Scalable CVD process for making 2-D molybdenum diselenide". Rdmag.com. 2014-04-04. http://www.rdmag.com/news/2014/04/scalable-cvd-process-making-2-d-molybdenum-diselenide. Retrieved 2014-04-09. 
  12. ↑ Choi, H. M. T.; Beck, V. A.; Pierce, N. A. (2014). "Next-Generation in Situ Hybridization Chain Reaction: Higher Gain, Lower Cost, Greater Durability". ACS Nano 8 (5): 4284–94. doi:10.1021/nn405717p. PMID 24712299. 
  13. ↑ "Home". http://www.mindat.org/. 



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