Chemistry:Tungsten diselenide

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Tungsten diselenide
STM of WSe2 on HOPG.jpg
Molybdenite-3D-balls.png
Identifiers
3D model (JSmol)
EC Number
  • 235-078-7
Properties
WSe2
Molar mass 341.76 g/mol
Appearance grey to black solid
Odor odorless
Density 9.32 g/cm3[1]
Melting point > 1200 °C
insoluble
Band gap ~1 eV (indirect, bulk)[2]
~1.7 eV (direct, monolayer)[3]
Structure
hP6, space group P63/mmc, No 194[1]
a = 0.3297 nm, c = 1.2982 nm
Trigonal prismatic (WIV)
Pyramidal (Se2−)
Thermochemistry
-185.3 kJ mol−1[4]
Hazards
Main hazards External MSDS
Related compounds
Other anions
 Tantalum 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):

Tungsten diselenide is an inorganic compound with the formula WSe2.[5] The compound adopts a hexagonal crystalline structure similar to molybdenum disulfide. The tungsten atoms are covalently bonded to six selenium ligands in a trigonal prismatic coordination sphere while each selenium is bonded to three tungsten atoms in a pyramidal geometry. The tungsten–selenium bond has a length of 0.2526 nm, and the distance between selenium atoms is 0.334 nm.[6] It is a well studied example of a layered material. The layers stack together via van der Waals interactions. WSe2 is a very stable semiconductor in the group-VI transition metal dichalcogenides.

Structure and properties

The hexagonal (P63/mmc) polymorph 2H-WSe2 is isotypic with hexagonal MoS2. The two-dimensional lattice structure has W and Se arranged periodically in layers with hexagonal symmetry. Similar to graphite, van der Waals interactions hold the layers together; however, the 2D-layers in WSe2 are not atomically thin. The large size of the W cation renders the lattice structure of WSe2 more sensitive to changes than MoS2.[7]

In addition to the typical semiconducting hexagonal structure, a second metallic polymorph of WSe2 exists. This phasem 1T-WSe2, is based on a tetragonal symmetry with one WSe2 layer per repeating unit. The 1T-WSe2 phase is less stable and transitions to the 2H-WSe2 phase.[7][8] WSe2 can form a fullerene-like structure.

The Young’s modulus vary greatly as a function of the number of layers in a flake. For a single monolayer, the reported Young’s modulus is 258.6 ± 38.3 GPa.[9]

Synthesis

Heating thin films of tungsten under pressure from gaseous selenium and high temperatures (>800 K) using the sputter deposition technique leads to the films crystallizing in hexagonal structures with the correct stoichiometric ratio.[10]

W + 2 Se → WSe2

Potential applications

Atomic image of a WSe2 monolayer showing hexagonal symmetry and three-fold defects. Scale bar: 2 nm (0.5 nm in the inset).[11]

The potential applications of transition metal dichalcogenides in solar cells and photonics are often discussed.[12] Bulk WSe2 has an optical band gap of ~1.35 eV with a temperature dependence of −4.6×10−4 eV/K.[13] WSe2 photoelectrodes are stable in both acidic and basic conditions, making them potentially useful in electrochemical solar cells.[14][15][16]

The properties of WSe2 monolayers differ from those of the bulk state, as is typical for semiconductors. Mechanically exfoliated monolayers of WSe2 are transparent photovoltaic materials with LED properties.[17] The resulting solar cells pass 95 percent of the incident light, with one tenth of the remaining five percent converted into electrical power.[18][19] The material can be changed from p-type to n-type by changing the voltage of an adjacent metal electrode from positive to negative, allowing devices made from it to have tunable bandgaps.[20]

See also

References

  1. ↑ 1.0 1.1 Agarwal, M. K.; Wani, P. A. (1979). "Growth conditions and crystal structure parameters of layer compounds in the series Mo1−xWxSe2". Materials Research Bulletin 14 (6): 825–830. doi:10.1016/0025-5408(79)90144-2. 
  2. ↑ Prakash, Abhijith; Appenzeller, Joerg (2017-02-28). "Bandgap Extraction and Device Analysis of Ionic Liquid Gated WSe2 Schottky Barrier Transistors". ACS Nano 11 (2): 1626–1632. doi:10.1021/acsnano.6b07360. ISSN 1936-0851. PMID 28191930. 
  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. ↑ O'Hare, P.A.G.; Lewis, Brett M.; parkinson, B.A. (June 1988). "Standard molar enthalpy of formation by fluorine-combustion calorimetry of tungsten diselenide (WSe2). Thermodynamics of the high-temperature vaporization of WSe2. Revised value of the standard molar enthalpy of formation of molybdenite (MoS2)" (in en). The Journal of Chemical Thermodynamics 20 (6): 681–691. doi:10.1016/0021-9614(88)90019-5. 
  5. ↑ Holleman, Arnold Frederik; Wiberg, Egon (2001), Wiberg, Nils, ed., Inorganic Chemistry, San Diego/Berlin: Academic Press/De Gruyter, ISBN 0-12-352651-5 
  6. ↑ Schutte, W.J.; De Boer, J.L.; Jellinek, F. (1986). "Crystal Structures of Tungsten Disulfide and Diselenide". Journal of Solid State Chemistry 70 (2): 207–209. doi:10.1016/0022-4596(87)90057-0. Bibcode: 1987JSSCh..70..207S. 
  7. ↑ 7.0 7.1 Eftekhari, Ali (2017). "Tungsten dichalcogenides (WS 2 , WSe 2 , and WTe 2 ): materials chemistry and applications" (in en). Journal of Materials Chemistry A 5 (35): 18299–18325. doi:10.1039/C7TA04268J. ISSN 2050-7488. http://xlink.rsc.org/?DOI=C7TA04268J. 
  8. ↑ Ma, Yuqiang; Liu, Bilu; Zhang, Anyi; Chen, Liang; Fathi, Mohammad; Shen, Chenfei; Abbas, Ahmad N.; Ge, Mingyuan et al. (2015-07-28). "Reversible Semiconducting-to-Metallic Phase Transition in Chemical Vapor Deposition Grown Monolayer WSe 2 and Applications for Devices" (in en). ACS Nano 9 (7): 7383–7391. doi:10.1021/acsnano.5b02399. ISSN 1936-0851. PMID 26125321. 
  9. ↑ Falin, Alexey; Holwill, Matthew; Lv, Haifeng; Gan, Wei; Cheng, Jun; Zhang, Rui; Qian, Dong; Barnett, Matthew R. et al. (23 February 2021). "Mechanical Properties of Atomically Thin Tungsten Dichalcogenides: WS 2 , WSe 2 , and WTe 2". ACS Nano 15 (2): 2600–2610. doi:10.1021/acsnano.0c07430. PMID 33503379. 
  10. ↑ Pouzet, J.; Bernede, J.C.; Khellil, A.; Essaidi, H.; Benhida, S. (1992). "Preparation and characterization of tungsten diselenide thin films". Thin Solid Films 208 (2): 252–259. doi:10.1016/0040-6090(92)90652-R. Bibcode: 1992TSF...208..252P. 
  11. ↑ Lin, Y. C.; Björkman, T. R.; Komsa, H. P.; Teng, P. Y.; Yeh, C. H.; Huang, F. S.; Lin, K. H.; Jadczak, J. et al. (2015). "Three-fold rotational defects in two-dimensional transition metal dichalcogenides". Nature Communications 6: 6736. doi:10.1038/ncomms7736. PMID 25832503. Bibcode: 2015NatCo...6.6736L. 
  12. ↑ Mak, Kin Fai; Shan, Jie (2016). "Photonics and optoelectronics of 2D semiconductor transition metal dichalcogenides". Nature Photonics 10 (4): 216–226. doi:10.1038/nphoton.2015.282. Bibcode: 2016NaPho..10..216M. 
  13. ↑ Upadhyayula, L.C.; Loferski, J.J.; Wold, A.; Giriat, W.; Kershaw, R. (1968). "Semiconducting Properties of Single Crystals of n- and p-Type Tungsten Diselenide (WSe2)". Journal of Applied Physics 39 (10): 353–358. doi:10.1063/1.1655829. Bibcode: 1968JAP....39.4736U. 
  14. ↑ Gobrecht, J.; Gerischer, H.; Tributsch, H. (1978). "Electrochemical Solar Cell Based on the d-Band Semiconductor Tungsten-Diselenide". Berichte der Bunsengesellschaft für physikalische Chemie 82 (12): 1331–1335. doi:10.1002/bbpc.19780821212. 
  15. ↑ Xia, Fengnian; Wang, Han; Xiao, Di; Dubey, Madan; Ramasubramaniam, Ashwin (2014). "Two-dimensional material nanophotonics". Nature Photonics 8 (12): 899–907. doi:10.1038/nphoton.2014.271. Bibcode: 2014NaPho...8..899X. 
  16. ↑ Zhang, Xin; Qiao, Xiao-Fen; Shi, Wei; Wu, Jiang-Bin; Jiang, De-Sheng; Tan, Ping-Heng (2015). "Phonon and Raman scattering of two-dimensional transition metal dichalcogenides from monolayer, multilayer to bulk material". Chem. Soc. Rev. 44 (9): 2757–85. doi:10.1039/C4CS00282B. PMID 25679474. Bibcode: 2015arXiv150200701Z. 
  17. ↑ Li, Hai; Wu, Jumiati; Yin, Zongyou; Zhang, Hua (2014). "Preparation and Applications of Mechanically Exfoliated Single-Layer and Multilayer MoS2 and WSe2 Nanosheets". Accounts of Chemical Research 47 (4): 1067–1075. doi:10.1021/ar4002312. PMID 24697842. 
  18. ↑ "Tungsten diselenide shows potential for ultrathin, flexible, semi-transparent solar cells". Gizmag.com. 11 March 2014. http://www.gizmag.com/tungsten-diselenide-solar-cells/31161. Retrieved 17 August 2014. 
  19. ↑ Florian Aigenr (10 March 2014). "Atomically thin solar cells" (Press release). Vienna University of Technology. Retrieved 18 August 2014.
  20. ↑ Lee, Sung-Joon; Lin, Zhaoyang; Huang, Jin; Choi, Christopher; Chen, Peng; Liu, Yuan; Guo, Jian; Jia, Chuancheng et al. (2020). "Programmable devices based on reversible solid-state doping of two-dimensional semiconductors with superionic silver iodide". Nature Electronics 3 (10): 630–637. doi:10.1038/s41928-020-00472-x. 



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