Abstract

We mechanically exfoliate mono- and few-layers of the transition metal dichalcogenides molybdenum disulfide, molybdenum diselenide, and tungsten diselenide. The exact number of layers is unambiguously determined by atomic force microscopy and high-resolution Raman spectroscopy. Strong photoluminescence emission is caused by the transition from an indirect band gap semiconductor of bulk material to a direct band gap semiconductor in atomically thin form.

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  1. A. K. Geim, “Graphene: status and prospects,” Science324(5934), 1530–1534 (2009).
    [CrossRef] [PubMed]
  2. K. S. Novoselov, D. Jiang, F. Schedin, T. J. Booth, V. V. Khotkevich, S. V. Morozov, and A. K. Geim, “Two-dimensional atomic crystals,” Proc. Natl. Acad. Sci. U.S.A.102(30), 10451–10453 (2005).
    [CrossRef] [PubMed]
  3. V. Podzorov, M. E. Gershenson, C. Kloc, R. Zeis, and E. Bucher, “High-mobility field-effect transistors based on transition metal dichalcogenides,” Appl. Phys. Lett.84(17), 3301–3304 (2004).
    [CrossRef]
  4. B. Radisavljevic, A. Radenovic, J. Brivio, V. Giacometti, and A. Kis, “Single-layer MoS2 transistors,” Nat. Nanotechnol.6(3), 147–150 (2011).
    [CrossRef] [PubMed]
  5. H. Fang, S. Chuang, T. C. Chang, K. Takei, T. Takahashi, and A. Javey, “High-performance single layered WSe₂ p-FETs with chemically doped contacts,” Nano Lett.12(7), 3788–3792 (2012).
    [CrossRef] [PubMed]
  6. K. F. Mak, C. Lee, J. Hone, J. Shan, and T. F. Heinz, “Atomically thin MoS₂: a new direct-gap semiconductor,” Phys. Rev. Lett.105(13), 136805 (2010).
    [CrossRef] [PubMed]
  7. A. Splendiani, L. Sun, Y. Zhang, T. Li, J. Kim, C. Y. Chim, G. Galli, and F. Wang, “Emerging photoluminescence in monolayer MoS2.,” Nano Lett.10(4), 1271–1275 (2010).
    [CrossRef] [PubMed]
  8. Z. Yin, H. Li, H. Li, L. Jiang, Y. Shi, Y. Sun, G. Lu, Q. Zhang, X. Chen, and H. Zhang, “Single-layer MoS2 phototransistors,” ACS Nano6(1), 74–80 (2012).
    [CrossRef] [PubMed]
  9. H. S. Lee, S. W. Min, Y. G. Chang, M. K. Park, T. Nam, H. Kim, J. H. Kim, S. Ryu, and S. Im, “MoS₂ nanosheet phototransistors with thickness-modulated optical energy gap,” Nano Lett.12(7), 3695–3700 (2012).
    [CrossRef] [PubMed]
  10. S. Tongay, J. Zhou, C. Ataca, K. Lo, T. S. Matthews, J. Li, J. C. Grossman, and J. Wu, “Thermally driven crossover from indirect toward direct bandgap in 2D semiconductors: MoSe2 versus MoS2.,” Nano Lett.12(11), 5576–5580 (2012).
    [CrossRef] [PubMed]
  11. H. Zeng, G.-B. Liu, J. Dai, Y. Yan, B. Zhu, R. He, L. Xie, S. Xu, X. Chen, W. Yao, and X. Cui, “Optical signature of symmetry variations and spin-valley coupling in atomically thin tungsten dichalcogenides,” arXiv:1208.5864 (2012).
  12. R. Späh, U. Elrod, M. Lux-Steiner, E. Bucher, and S. Wagner, “pn junctions in tungsten diselenide,” Appl. Phys. Lett.43(1), 79–81 (1983).
    [CrossRef]
  13. R. Gordon, D. Yang, E. Crozier, D. Jiang, and R. Frindt, “Structures of exfoliated single layers of WS2, MoS2, and MoSe2 in aqueous suspension,” Phys. Rev. B65(12), 125407 (2002).
    [CrossRef]
  14. A. R. Beal, W. Y. Liang, and H. P. Hughes, “Kramers-Kronig analysis of the reflectivity spectra of 3R-WS2 and 2H-WSe2,” J. Phys.C, 9, 2449–2457 (1976).
  15. A. Castellanos-Gomez, N. Agraït, and G. Rubio-Bollinger, “Optical identification of atomically thin dichalcogenide crystals,” Appl. Phys. Lett.96(21), 213116 (2010).
    [CrossRef]
  16. M. M. Benameur, B. Radisavljevic, J. S. Héron, S. Sahoo, H. Berger, and A. Kis, “Visibility of dichalcogenide nanolayers,” Nanotechnology22(12), 125706 (2011).
    [CrossRef] [PubMed]
  17. C. Lee, H. Yan, L. E. Brus, T. F. Heinz, J. Hone, and S. Ryu, “Anomalous lattice vibrations of single- and few-layer MoS2.,” ACS Nano4(5), 2695–2700 (2010).
    [CrossRef] [PubMed]
  18. J. Verble and T. Wieting, “Lattice mode degeneracy in MoS2 and other layer compounds,” Phys. Rev. Lett.25(6), 362–365 (1970).
    [CrossRef]
  19. G. Frey, R. Tenne, M. Matthews, M. Dresselhaus, and G. Dresselhaus, “Raman and resonance Raman investigation of MoS2 nanoparticles,” Phys. Rev. B60(4), 2883–2892 (1999).
    [CrossRef]
  20. T. Wieting and J. Verble, “Infrared and Raman studies of long-wavelength optical phonons in hexagonal MoS2,” Phys. Rev. B3(12), 4286–4292 (1971).
    [CrossRef]
  21. C. Ataca, M. Topsakal, E. Aktürk, and S. Ciraci, “A comparative study of lattice dynamics of three- and two-dimensional MoS2,” J. Phys. Chem. C115(33), 16354–16361 (2011).
    [CrossRef]
  22. T. Korn, S. Heydrich, M. Hirmer, J. Schmutzler, and C. Schüller, “Low-temperature photocarrier dynamics in monolayer MoS2,” Appl. Phys. Lett.99(10), 102109 (2011).
    [CrossRef]
  23. H. Li, Q. Zhang, C. C. R. Yap, B. K. Tay, T. H. T. Edwin, A. Olivier, and D. Baillargeat, “From bulk to monolayer MoS2: evolution of Raman scattering,” Adv. Funct. Mater.22(7), 1385–1390 (2012).
    [CrossRef]
  24. A. Molina-Sánchez and L. Wirtz, “Phonons in single-layer and few-layer MoS2 and WS2,” Phys. Rev. B84(15), 155413 (2011).
    [CrossRef]
  25. T. Sekine, M. Izumi, T. Nakashizu, K. Uchinokura, and E. Matsuura, “Raman scattering and infrared reflectance in 2H-MoSe2,” J. Phys. Soc. Jpn.49(3), 1069–1077 (1980).
    [CrossRef]
  26. T. J. Wieting, A. Grisel, and F. Levy, “Interlayer bonding and localized charge in MoSe2 and α-MoTe2,” Physica B+C99(1-4), 337–342 (1980).
    [CrossRef]
  27. S. Sugai and T. Ueda, “High-pressure Raman spectroscopy in the layered materials 2H-MoS2, 2H-MoSe2, and 2H-MoTe2,” Phys. Rev. B26(12), 6554–6558 (1982).
    [CrossRef]
  28. Y. Ding, Y. Wang, J. Ni, L. Shi, S. Shi, and W. Tang, “First principles study of structural, vibrational and electronic properties of graphene-like MX2 (M=Mo, Nb, W, Ta; X=S, Se, Te) monolayers,” Physica B406(11), 2254–2260 (2011).
    [CrossRef]
  29. H. S. S. R. Matte, B. Plowman, R. Datta, and C. N. R. Rao, “Graphene analogues of layered metal selenides,” Dalton Trans.40(40), 10322–10325 (2011).
    [CrossRef] [PubMed]
  30. D. G. Mead and J. C. Irwin, “Long wavelength optic phonons in WSe2,” Can. J. Phys.55(5), 379–382 (1977).
    [CrossRef]
  31. A. Kuc, N. Zibouche, and T. Heine, “Influence of quantum confinement on the electronic structure of the transition metal sulfide TS2,” Phys. Rev. B83(24), 245213 (2011).
    [CrossRef]
  32. R. Coehoorn, C. Haas, and R. de Groot, “Electronic structure of MoSe2, MoS2, and WSe2. II. The nature of the optical band gaps,” Phys. Rev. B Condens. Matter35(12), 6203–6206 (1987).
    [CrossRef] [PubMed]
  33. A. R. Beal and H. P. Hughes, “Kramers-Kronig analysis of the reflectivity spectra of 2H-MoS2, 2H-MoSe2 and 2H-MoTe2,” J. Phys. Chem.12, 881–890 (1979).
  34. A. Anedda and E. Fortin, “Exciton spectra in MoSe2,” J. Phys. Chem. Solids41(8), 865–869 (1980).
    [CrossRef]
  35. J. Martin, N. Akerman, G. Ulbricht, T. Lohmann, J. H. Smet, K. von Klitzing, and A. Yacoby, “Observation of electron–hole puddles in graphene using a scanning single-electron transistor,” Nat. Phys.4(2), 144–148 (2008).
    [CrossRef]
  36. Y. Ma, Y. Dai, M. Guo, C. Niu, J. Lu, and B. Huang, “Electronic and magnetic properties of perfect, vacancy-doped, and nonmetal adsorbed MoSe2, MoTe2 and WS2 monolayers,” Phys. Chem. Chem. Phys.13(34), 15546–15553 (2011).
    [CrossRef] [PubMed]
  37. W. S. Yun, S. Han, S. C. Hong, I. G. Kim, and J. Lee, “Thickness and strain effects on electronic structures of transition metal dichalcogenides: 2H-MX2 semiconductors (M = Mo, W; X = S, Se, Te),” Phys. Rev. B85(3), 033305 (2012).
    [CrossRef]
  38. G. Plechinger, F. X. Schrettenbrunner, J. Eroms, D. Weiss, C. Schüller, and T. Korn, “Low-temperature photoluminescence of oxide-covered single-layer MoS2,” Phys. Status Solidi (RRL)6(3), 126–128 (2012).
    [CrossRef]
  39. M. P. Deshpande, G. K. Solanki, and M. K. Agarwal, “Optical band gap in tungsten diselenide single crystals intercalated by indium,” Mater. Lett.43(1-2), 66–72 (2000).
    [CrossRef]
  40. J. A. Wilson and A. D. Yoffe, “The transition metal dichalcogenides discussion and interpretation of the observed optical, electrical and structural properties,” Adv. Phys.18(73), 193–335 (1969).
    [CrossRef]

2012

H. Fang, S. Chuang, T. C. Chang, K. Takei, T. Takahashi, and A. Javey, “High-performance single layered WSe₂ p-FETs with chemically doped contacts,” Nano Lett.12(7), 3788–3792 (2012).
[CrossRef] [PubMed]

Z. Yin, H. Li, H. Li, L. Jiang, Y. Shi, Y. Sun, G. Lu, Q. Zhang, X. Chen, and H. Zhang, “Single-layer MoS2 phototransistors,” ACS Nano6(1), 74–80 (2012).
[CrossRef] [PubMed]

H. S. Lee, S. W. Min, Y. G. Chang, M. K. Park, T. Nam, H. Kim, J. H. Kim, S. Ryu, and S. Im, “MoS₂ nanosheet phototransistors with thickness-modulated optical energy gap,” Nano Lett.12(7), 3695–3700 (2012).
[CrossRef] [PubMed]

S. Tongay, J. Zhou, C. Ataca, K. Lo, T. S. Matthews, J. Li, J. C. Grossman, and J. Wu, “Thermally driven crossover from indirect toward direct bandgap in 2D semiconductors: MoSe2 versus MoS2.,” Nano Lett.12(11), 5576–5580 (2012).
[CrossRef] [PubMed]

H. Li, Q. Zhang, C. C. R. Yap, B. K. Tay, T. H. T. Edwin, A. Olivier, and D. Baillargeat, “From bulk to monolayer MoS2: evolution of Raman scattering,” Adv. Funct. Mater.22(7), 1385–1390 (2012).
[CrossRef]

W. S. Yun, S. Han, S. C. Hong, I. G. Kim, and J. Lee, “Thickness and strain effects on electronic structures of transition metal dichalcogenides: 2H-MX2 semiconductors (M = Mo, W; X = S, Se, Te),” Phys. Rev. B85(3), 033305 (2012).
[CrossRef]

G. Plechinger, F. X. Schrettenbrunner, J. Eroms, D. Weiss, C. Schüller, and T. Korn, “Low-temperature photoluminescence of oxide-covered single-layer MoS2,” Phys. Status Solidi (RRL)6(3), 126–128 (2012).
[CrossRef]

2011

A. Kuc, N. Zibouche, and T. Heine, “Influence of quantum confinement on the electronic structure of the transition metal sulfide TS2,” Phys. Rev. B83(24), 245213 (2011).
[CrossRef]

A. Molina-Sánchez and L. Wirtz, “Phonons in single-layer and few-layer MoS2 and WS2,” Phys. Rev. B84(15), 155413 (2011).
[CrossRef]

C. Ataca, M. Topsakal, E. Aktürk, and S. Ciraci, “A comparative study of lattice dynamics of three- and two-dimensional MoS2,” J. Phys. Chem. C115(33), 16354–16361 (2011).
[CrossRef]

T. Korn, S. Heydrich, M. Hirmer, J. Schmutzler, and C. Schüller, “Low-temperature photocarrier dynamics in monolayer MoS2,” Appl. Phys. Lett.99(10), 102109 (2011).
[CrossRef]

Y. Ding, Y. Wang, J. Ni, L. Shi, S. Shi, and W. Tang, “First principles study of structural, vibrational and electronic properties of graphene-like MX2 (M=Mo, Nb, W, Ta; X=S, Se, Te) monolayers,” Physica B406(11), 2254–2260 (2011).
[CrossRef]

H. S. S. R. Matte, B. Plowman, R. Datta, and C. N. R. Rao, “Graphene analogues of layered metal selenides,” Dalton Trans.40(40), 10322–10325 (2011).
[CrossRef] [PubMed]

B. Radisavljevic, A. Radenovic, J. Brivio, V. Giacometti, and A. Kis, “Single-layer MoS2 transistors,” Nat. Nanotechnol.6(3), 147–150 (2011).
[CrossRef] [PubMed]

M. M. Benameur, B. Radisavljevic, J. S. Héron, S. Sahoo, H. Berger, and A. Kis, “Visibility of dichalcogenide nanolayers,” Nanotechnology22(12), 125706 (2011).
[CrossRef] [PubMed]

Y. Ma, Y. Dai, M. Guo, C. Niu, J. Lu, and B. Huang, “Electronic and magnetic properties of perfect, vacancy-doped, and nonmetal adsorbed MoSe2, MoTe2 and WS2 monolayers,” Phys. Chem. Chem. Phys.13(34), 15546–15553 (2011).
[CrossRef] [PubMed]

2010

C. Lee, H. Yan, L. E. Brus, T. F. Heinz, J. Hone, and S. Ryu, “Anomalous lattice vibrations of single- and few-layer MoS2.,” ACS Nano4(5), 2695–2700 (2010).
[CrossRef] [PubMed]

A. Castellanos-Gomez, N. Agraït, and G. Rubio-Bollinger, “Optical identification of atomically thin dichalcogenide crystals,” Appl. Phys. Lett.96(21), 213116 (2010).
[CrossRef]

K. F. Mak, C. Lee, J. Hone, J. Shan, and T. F. Heinz, “Atomically thin MoS₂: a new direct-gap semiconductor,” Phys. Rev. Lett.105(13), 136805 (2010).
[CrossRef] [PubMed]

A. Splendiani, L. Sun, Y. Zhang, T. Li, J. Kim, C. Y. Chim, G. Galli, and F. Wang, “Emerging photoluminescence in monolayer MoS2.,” Nano Lett.10(4), 1271–1275 (2010).
[CrossRef] [PubMed]

2009

A. K. Geim, “Graphene: status and prospects,” Science324(5934), 1530–1534 (2009).
[CrossRef] [PubMed]

2008

J. Martin, N. Akerman, G. Ulbricht, T. Lohmann, J. H. Smet, K. von Klitzing, and A. Yacoby, “Observation of electron–hole puddles in graphene using a scanning single-electron transistor,” Nat. Phys.4(2), 144–148 (2008).
[CrossRef]

2005

K. S. Novoselov, D. Jiang, F. Schedin, T. J. Booth, V. V. Khotkevich, S. V. Morozov, and A. K. Geim, “Two-dimensional atomic crystals,” Proc. Natl. Acad. Sci. U.S.A.102(30), 10451–10453 (2005).
[CrossRef] [PubMed]

2004

V. Podzorov, M. E. Gershenson, C. Kloc, R. Zeis, and E. Bucher, “High-mobility field-effect transistors based on transition metal dichalcogenides,” Appl. Phys. Lett.84(17), 3301–3304 (2004).
[CrossRef]

2002

R. Gordon, D. Yang, E. Crozier, D. Jiang, and R. Frindt, “Structures of exfoliated single layers of WS2, MoS2, and MoSe2 in aqueous suspension,” Phys. Rev. B65(12), 125407 (2002).
[CrossRef]

2000

M. P. Deshpande, G. K. Solanki, and M. K. Agarwal, “Optical band gap in tungsten diselenide single crystals intercalated by indium,” Mater. Lett.43(1-2), 66–72 (2000).
[CrossRef]

1999

G. Frey, R. Tenne, M. Matthews, M. Dresselhaus, and G. Dresselhaus, “Raman and resonance Raman investigation of MoS2 nanoparticles,” Phys. Rev. B60(4), 2883–2892 (1999).
[CrossRef]

1987

R. Coehoorn, C. Haas, and R. de Groot, “Electronic structure of MoSe2, MoS2, and WSe2. II. The nature of the optical band gaps,” Phys. Rev. B Condens. Matter35(12), 6203–6206 (1987).
[CrossRef] [PubMed]

1983

R. Späh, U. Elrod, M. Lux-Steiner, E. Bucher, and S. Wagner, “pn junctions in tungsten diselenide,” Appl. Phys. Lett.43(1), 79–81 (1983).
[CrossRef]

1982

S. Sugai and T. Ueda, “High-pressure Raman spectroscopy in the layered materials 2H-MoS2, 2H-MoSe2, and 2H-MoTe2,” Phys. Rev. B26(12), 6554–6558 (1982).
[CrossRef]

1980

A. Anedda and E. Fortin, “Exciton spectra in MoSe2,” J. Phys. Chem. Solids41(8), 865–869 (1980).
[CrossRef]

T. Sekine, M. Izumi, T. Nakashizu, K. Uchinokura, and E. Matsuura, “Raman scattering and infrared reflectance in 2H-MoSe2,” J. Phys. Soc. Jpn.49(3), 1069–1077 (1980).
[CrossRef]

T. J. Wieting, A. Grisel, and F. Levy, “Interlayer bonding and localized charge in MoSe2 and α-MoTe2,” Physica B+C99(1-4), 337–342 (1980).
[CrossRef]

1979

A. R. Beal and H. P. Hughes, “Kramers-Kronig analysis of the reflectivity spectra of 2H-MoS2, 2H-MoSe2 and 2H-MoTe2,” J. Phys. Chem.12, 881–890 (1979).

1977

D. G. Mead and J. C. Irwin, “Long wavelength optic phonons in WSe2,” Can. J. Phys.55(5), 379–382 (1977).
[CrossRef]

1976

A. R. Beal, W. Y. Liang, and H. P. Hughes, “Kramers-Kronig analysis of the reflectivity spectra of 3R-WS2 and 2H-WSe2,” J. Phys.C, 9, 2449–2457 (1976).

1971

T. Wieting and J. Verble, “Infrared and Raman studies of long-wavelength optical phonons in hexagonal MoS2,” Phys. Rev. B3(12), 4286–4292 (1971).
[CrossRef]

1970

J. Verble and T. Wieting, “Lattice mode degeneracy in MoS2 and other layer compounds,” Phys. Rev. Lett.25(6), 362–365 (1970).
[CrossRef]

1969

J. A. Wilson and A. D. Yoffe, “The transition metal dichalcogenides discussion and interpretation of the observed optical, electrical and structural properties,” Adv. Phys.18(73), 193–335 (1969).
[CrossRef]

Agarwal, M. K.

M. P. Deshpande, G. K. Solanki, and M. K. Agarwal, “Optical band gap in tungsten diselenide single crystals intercalated by indium,” Mater. Lett.43(1-2), 66–72 (2000).
[CrossRef]

Agraït, N.

A. Castellanos-Gomez, N. Agraït, and G. Rubio-Bollinger, “Optical identification of atomically thin dichalcogenide crystals,” Appl. Phys. Lett.96(21), 213116 (2010).
[CrossRef]

Akerman, N.

J. Martin, N. Akerman, G. Ulbricht, T. Lohmann, J. H. Smet, K. von Klitzing, and A. Yacoby, “Observation of electron–hole puddles in graphene using a scanning single-electron transistor,” Nat. Phys.4(2), 144–148 (2008).
[CrossRef]

Aktürk, E.

C. Ataca, M. Topsakal, E. Aktürk, and S. Ciraci, “A comparative study of lattice dynamics of three- and two-dimensional MoS2,” J. Phys. Chem. C115(33), 16354–16361 (2011).
[CrossRef]

Anedda, A.

A. Anedda and E. Fortin, “Exciton spectra in MoSe2,” J. Phys. Chem. Solids41(8), 865–869 (1980).
[CrossRef]

Ataca, C.

S. Tongay, J. Zhou, C. Ataca, K. Lo, T. S. Matthews, J. Li, J. C. Grossman, and J. Wu, “Thermally driven crossover from indirect toward direct bandgap in 2D semiconductors: MoSe2 versus MoS2.,” Nano Lett.12(11), 5576–5580 (2012).
[CrossRef] [PubMed]

C. Ataca, M. Topsakal, E. Aktürk, and S. Ciraci, “A comparative study of lattice dynamics of three- and two-dimensional MoS2,” J. Phys. Chem. C115(33), 16354–16361 (2011).
[CrossRef]

Baillargeat, D.

H. Li, Q. Zhang, C. C. R. Yap, B. K. Tay, T. H. T. Edwin, A. Olivier, and D. Baillargeat, “From bulk to monolayer MoS2: evolution of Raman scattering,” Adv. Funct. Mater.22(7), 1385–1390 (2012).
[CrossRef]

Beal, A. R.

A. R. Beal and H. P. Hughes, “Kramers-Kronig analysis of the reflectivity spectra of 2H-MoS2, 2H-MoSe2 and 2H-MoTe2,” J. Phys. Chem.12, 881–890 (1979).

A. R. Beal, W. Y. Liang, and H. P. Hughes, “Kramers-Kronig analysis of the reflectivity spectra of 3R-WS2 and 2H-WSe2,” J. Phys.C, 9, 2449–2457 (1976).

Benameur, M. M.

M. M. Benameur, B. Radisavljevic, J. S. Héron, S. Sahoo, H. Berger, and A. Kis, “Visibility of dichalcogenide nanolayers,” Nanotechnology22(12), 125706 (2011).
[CrossRef] [PubMed]

Berger, H.

M. M. Benameur, B. Radisavljevic, J. S. Héron, S. Sahoo, H. Berger, and A. Kis, “Visibility of dichalcogenide nanolayers,” Nanotechnology22(12), 125706 (2011).
[CrossRef] [PubMed]

Booth, T. J.

K. S. Novoselov, D. Jiang, F. Schedin, T. J. Booth, V. V. Khotkevich, S. V. Morozov, and A. K. Geim, “Two-dimensional atomic crystals,” Proc. Natl. Acad. Sci. U.S.A.102(30), 10451–10453 (2005).
[CrossRef] [PubMed]

Brivio, J.

B. Radisavljevic, A. Radenovic, J. Brivio, V. Giacometti, and A. Kis, “Single-layer MoS2 transistors,” Nat. Nanotechnol.6(3), 147–150 (2011).
[CrossRef] [PubMed]

Brus, L. E.

C. Lee, H. Yan, L. E. Brus, T. F. Heinz, J. Hone, and S. Ryu, “Anomalous lattice vibrations of single- and few-layer MoS2.,” ACS Nano4(5), 2695–2700 (2010).
[CrossRef] [PubMed]

Bucher, E.

V. Podzorov, M. E. Gershenson, C. Kloc, R. Zeis, and E. Bucher, “High-mobility field-effect transistors based on transition metal dichalcogenides,” Appl. Phys. Lett.84(17), 3301–3304 (2004).
[CrossRef]

R. Späh, U. Elrod, M. Lux-Steiner, E. Bucher, and S. Wagner, “pn junctions in tungsten diselenide,” Appl. Phys. Lett.43(1), 79–81 (1983).
[CrossRef]

Castellanos-Gomez, A.

A. Castellanos-Gomez, N. Agraït, and G. Rubio-Bollinger, “Optical identification of atomically thin dichalcogenide crystals,” Appl. Phys. Lett.96(21), 213116 (2010).
[CrossRef]

Chang, T. C.

H. Fang, S. Chuang, T. C. Chang, K. Takei, T. Takahashi, and A. Javey, “High-performance single layered WSe₂ p-FETs with chemically doped contacts,” Nano Lett.12(7), 3788–3792 (2012).
[CrossRef] [PubMed]

Chang, Y. G.

H. S. Lee, S. W. Min, Y. G. Chang, M. K. Park, T. Nam, H. Kim, J. H. Kim, S. Ryu, and S. Im, “MoS₂ nanosheet phototransistors with thickness-modulated optical energy gap,” Nano Lett.12(7), 3695–3700 (2012).
[CrossRef] [PubMed]

Chen, X.

Z. Yin, H. Li, H. Li, L. Jiang, Y. Shi, Y. Sun, G. Lu, Q. Zhang, X. Chen, and H. Zhang, “Single-layer MoS2 phototransistors,” ACS Nano6(1), 74–80 (2012).
[CrossRef] [PubMed]

Chim, C. Y.

A. Splendiani, L. Sun, Y. Zhang, T. Li, J. Kim, C. Y. Chim, G. Galli, and F. Wang, “Emerging photoluminescence in monolayer MoS2.,” Nano Lett.10(4), 1271–1275 (2010).
[CrossRef] [PubMed]

Chuang, S.

H. Fang, S. Chuang, T. C. Chang, K. Takei, T. Takahashi, and A. Javey, “High-performance single layered WSe₂ p-FETs with chemically doped contacts,” Nano Lett.12(7), 3788–3792 (2012).
[CrossRef] [PubMed]

Ciraci, S.

C. Ataca, M. Topsakal, E. Aktürk, and S. Ciraci, “A comparative study of lattice dynamics of three- and two-dimensional MoS2,” J. Phys. Chem. C115(33), 16354–16361 (2011).
[CrossRef]

Coehoorn, R.

R. Coehoorn, C. Haas, and R. de Groot, “Electronic structure of MoSe2, MoS2, and WSe2. II. The nature of the optical band gaps,” Phys. Rev. B Condens. Matter35(12), 6203–6206 (1987).
[CrossRef] [PubMed]

Crozier, E.

R. Gordon, D. Yang, E. Crozier, D. Jiang, and R. Frindt, “Structures of exfoliated single layers of WS2, MoS2, and MoSe2 in aqueous suspension,” Phys. Rev. B65(12), 125407 (2002).
[CrossRef]

Dai, Y.

Y. Ma, Y. Dai, M. Guo, C. Niu, J. Lu, and B. Huang, “Electronic and magnetic properties of perfect, vacancy-doped, and nonmetal adsorbed MoSe2, MoTe2 and WS2 monolayers,” Phys. Chem. Chem. Phys.13(34), 15546–15553 (2011).
[CrossRef] [PubMed]

Datta, R.

H. S. S. R. Matte, B. Plowman, R. Datta, and C. N. R. Rao, “Graphene analogues of layered metal selenides,” Dalton Trans.40(40), 10322–10325 (2011).
[CrossRef] [PubMed]

de Groot, R.

R. Coehoorn, C. Haas, and R. de Groot, “Electronic structure of MoSe2, MoS2, and WSe2. II. The nature of the optical band gaps,” Phys. Rev. B Condens. Matter35(12), 6203–6206 (1987).
[CrossRef] [PubMed]

Deshpande, M. P.

M. P. Deshpande, G. K. Solanki, and M. K. Agarwal, “Optical band gap in tungsten diselenide single crystals intercalated by indium,” Mater. Lett.43(1-2), 66–72 (2000).
[CrossRef]

Ding, Y.

Y. Ding, Y. Wang, J. Ni, L. Shi, S. Shi, and W. Tang, “First principles study of structural, vibrational and electronic properties of graphene-like MX2 (M=Mo, Nb, W, Ta; X=S, Se, Te) monolayers,” Physica B406(11), 2254–2260 (2011).
[CrossRef]

Dresselhaus, G.

G. Frey, R. Tenne, M. Matthews, M. Dresselhaus, and G. Dresselhaus, “Raman and resonance Raman investigation of MoS2 nanoparticles,” Phys. Rev. B60(4), 2883–2892 (1999).
[CrossRef]

Dresselhaus, M.

G. Frey, R. Tenne, M. Matthews, M. Dresselhaus, and G. Dresselhaus, “Raman and resonance Raman investigation of MoS2 nanoparticles,” Phys. Rev. B60(4), 2883–2892 (1999).
[CrossRef]

Edwin, T. H. T.

H. Li, Q. Zhang, C. C. R. Yap, B. K. Tay, T. H. T. Edwin, A. Olivier, and D. Baillargeat, “From bulk to monolayer MoS2: evolution of Raman scattering,” Adv. Funct. Mater.22(7), 1385–1390 (2012).
[CrossRef]

Elrod, U.

R. Späh, U. Elrod, M. Lux-Steiner, E. Bucher, and S. Wagner, “pn junctions in tungsten diselenide,” Appl. Phys. Lett.43(1), 79–81 (1983).
[CrossRef]

Eroms, J.

G. Plechinger, F. X. Schrettenbrunner, J. Eroms, D. Weiss, C. Schüller, and T. Korn, “Low-temperature photoluminescence of oxide-covered single-layer MoS2,” Phys. Status Solidi (RRL)6(3), 126–128 (2012).
[CrossRef]

Fang, H.

H. Fang, S. Chuang, T. C. Chang, K. Takei, T. Takahashi, and A. Javey, “High-performance single layered WSe₂ p-FETs with chemically doped contacts,” Nano Lett.12(7), 3788–3792 (2012).
[CrossRef] [PubMed]

Fortin, E.

A. Anedda and E. Fortin, “Exciton spectra in MoSe2,” J. Phys. Chem. Solids41(8), 865–869 (1980).
[CrossRef]

Frey, G.

G. Frey, R. Tenne, M. Matthews, M. Dresselhaus, and G. Dresselhaus, “Raman and resonance Raman investigation of MoS2 nanoparticles,” Phys. Rev. B60(4), 2883–2892 (1999).
[CrossRef]

Frindt, R.

R. Gordon, D. Yang, E. Crozier, D. Jiang, and R. Frindt, “Structures of exfoliated single layers of WS2, MoS2, and MoSe2 in aqueous suspension,” Phys. Rev. B65(12), 125407 (2002).
[CrossRef]

Galli, G.

A. Splendiani, L. Sun, Y. Zhang, T. Li, J. Kim, C. Y. Chim, G. Galli, and F. Wang, “Emerging photoluminescence in monolayer MoS2.,” Nano Lett.10(4), 1271–1275 (2010).
[CrossRef] [PubMed]

Geim, A. K.

A. K. Geim, “Graphene: status and prospects,” Science324(5934), 1530–1534 (2009).
[CrossRef] [PubMed]

K. S. Novoselov, D. Jiang, F. Schedin, T. J. Booth, V. V. Khotkevich, S. V. Morozov, and A. K. Geim, “Two-dimensional atomic crystals,” Proc. Natl. Acad. Sci. U.S.A.102(30), 10451–10453 (2005).
[CrossRef] [PubMed]

Gershenson, M. E.

V. Podzorov, M. E. Gershenson, C. Kloc, R. Zeis, and E. Bucher, “High-mobility field-effect transistors based on transition metal dichalcogenides,” Appl. Phys. Lett.84(17), 3301–3304 (2004).
[CrossRef]

Giacometti, V.

B. Radisavljevic, A. Radenovic, J. Brivio, V. Giacometti, and A. Kis, “Single-layer MoS2 transistors,” Nat. Nanotechnol.6(3), 147–150 (2011).
[CrossRef] [PubMed]

Gordon, R.

R. Gordon, D. Yang, E. Crozier, D. Jiang, and R. Frindt, “Structures of exfoliated single layers of WS2, MoS2, and MoSe2 in aqueous suspension,” Phys. Rev. B65(12), 125407 (2002).
[CrossRef]

Grisel, A.

T. J. Wieting, A. Grisel, and F. Levy, “Interlayer bonding and localized charge in MoSe2 and α-MoTe2,” Physica B+C99(1-4), 337–342 (1980).
[CrossRef]

Grossman, J. C.

S. Tongay, J. Zhou, C. Ataca, K. Lo, T. S. Matthews, J. Li, J. C. Grossman, and J. Wu, “Thermally driven crossover from indirect toward direct bandgap in 2D semiconductors: MoSe2 versus MoS2.,” Nano Lett.12(11), 5576–5580 (2012).
[CrossRef] [PubMed]

Guo, M.

Y. Ma, Y. Dai, M. Guo, C. Niu, J. Lu, and B. Huang, “Electronic and magnetic properties of perfect, vacancy-doped, and nonmetal adsorbed MoSe2, MoTe2 and WS2 monolayers,” Phys. Chem. Chem. Phys.13(34), 15546–15553 (2011).
[CrossRef] [PubMed]

Haas, C.

R. Coehoorn, C. Haas, and R. de Groot, “Electronic structure of MoSe2, MoS2, and WSe2. II. The nature of the optical band gaps,” Phys. Rev. B Condens. Matter35(12), 6203–6206 (1987).
[CrossRef] [PubMed]

Han, S.

W. S. Yun, S. Han, S. C. Hong, I. G. Kim, and J. Lee, “Thickness and strain effects on electronic structures of transition metal dichalcogenides: 2H-MX2 semiconductors (M = Mo, W; X = S, Se, Te),” Phys. Rev. B85(3), 033305 (2012).
[CrossRef]

Heine, T.

A. Kuc, N. Zibouche, and T. Heine, “Influence of quantum confinement on the electronic structure of the transition metal sulfide TS2,” Phys. Rev. B83(24), 245213 (2011).
[CrossRef]

Heinz, T. F.

K. F. Mak, C. Lee, J. Hone, J. Shan, and T. F. Heinz, “Atomically thin MoS₂: a new direct-gap semiconductor,” Phys. Rev. Lett.105(13), 136805 (2010).
[CrossRef] [PubMed]

C. Lee, H. Yan, L. E. Brus, T. F. Heinz, J. Hone, and S. Ryu, “Anomalous lattice vibrations of single- and few-layer MoS2.,” ACS Nano4(5), 2695–2700 (2010).
[CrossRef] [PubMed]

Héron, J. S.

M. M. Benameur, B. Radisavljevic, J. S. Héron, S. Sahoo, H. Berger, and A. Kis, “Visibility of dichalcogenide nanolayers,” Nanotechnology22(12), 125706 (2011).
[CrossRef] [PubMed]

Heydrich, S.

T. Korn, S. Heydrich, M. Hirmer, J. Schmutzler, and C. Schüller, “Low-temperature photocarrier dynamics in monolayer MoS2,” Appl. Phys. Lett.99(10), 102109 (2011).
[CrossRef]

Hirmer, M.

T. Korn, S. Heydrich, M. Hirmer, J. Schmutzler, and C. Schüller, “Low-temperature photocarrier dynamics in monolayer MoS2,” Appl. Phys. Lett.99(10), 102109 (2011).
[CrossRef]

Hone, J.

C. Lee, H. Yan, L. E. Brus, T. F. Heinz, J. Hone, and S. Ryu, “Anomalous lattice vibrations of single- and few-layer MoS2.,” ACS Nano4(5), 2695–2700 (2010).
[CrossRef] [PubMed]

K. F. Mak, C. Lee, J. Hone, J. Shan, and T. F. Heinz, “Atomically thin MoS₂: a new direct-gap semiconductor,” Phys. Rev. Lett.105(13), 136805 (2010).
[CrossRef] [PubMed]

Hong, S. C.

W. S. Yun, S. Han, S. C. Hong, I. G. Kim, and J. Lee, “Thickness and strain effects on electronic structures of transition metal dichalcogenides: 2H-MX2 semiconductors (M = Mo, W; X = S, Se, Te),” Phys. Rev. B85(3), 033305 (2012).
[CrossRef]

Huang, B.

Y. Ma, Y. Dai, M. Guo, C. Niu, J. Lu, and B. Huang, “Electronic and magnetic properties of perfect, vacancy-doped, and nonmetal adsorbed MoSe2, MoTe2 and WS2 monolayers,” Phys. Chem. Chem. Phys.13(34), 15546–15553 (2011).
[CrossRef] [PubMed]

Hughes, H. P.

A. R. Beal and H. P. Hughes, “Kramers-Kronig analysis of the reflectivity spectra of 2H-MoS2, 2H-MoSe2 and 2H-MoTe2,” J. Phys. Chem.12, 881–890 (1979).

A. R. Beal, W. Y. Liang, and H. P. Hughes, “Kramers-Kronig analysis of the reflectivity spectra of 3R-WS2 and 2H-WSe2,” J. Phys.C, 9, 2449–2457 (1976).

Im, S.

H. S. Lee, S. W. Min, Y. G. Chang, M. K. Park, T. Nam, H. Kim, J. H. Kim, S. Ryu, and S. Im, “MoS₂ nanosheet phototransistors with thickness-modulated optical energy gap,” Nano Lett.12(7), 3695–3700 (2012).
[CrossRef] [PubMed]

Irwin, J. C.

D. G. Mead and J. C. Irwin, “Long wavelength optic phonons in WSe2,” Can. J. Phys.55(5), 379–382 (1977).
[CrossRef]

Izumi, M.

T. Sekine, M. Izumi, T. Nakashizu, K. Uchinokura, and E. Matsuura, “Raman scattering and infrared reflectance in 2H-MoSe2,” J. Phys. Soc. Jpn.49(3), 1069–1077 (1980).
[CrossRef]

Javey, A.

H. Fang, S. Chuang, T. C. Chang, K. Takei, T. Takahashi, and A. Javey, “High-performance single layered WSe₂ p-FETs with chemically doped contacts,” Nano Lett.12(7), 3788–3792 (2012).
[CrossRef] [PubMed]

Jiang, D.

K. S. Novoselov, D. Jiang, F. Schedin, T. J. Booth, V. V. Khotkevich, S. V. Morozov, and A. K. Geim, “Two-dimensional atomic crystals,” Proc. Natl. Acad. Sci. U.S.A.102(30), 10451–10453 (2005).
[CrossRef] [PubMed]

R. Gordon, D. Yang, E. Crozier, D. Jiang, and R. Frindt, “Structures of exfoliated single layers of WS2, MoS2, and MoSe2 in aqueous suspension,” Phys. Rev. B65(12), 125407 (2002).
[CrossRef]

Jiang, L.

Z. Yin, H. Li, H. Li, L. Jiang, Y. Shi, Y. Sun, G. Lu, Q. Zhang, X. Chen, and H. Zhang, “Single-layer MoS2 phototransistors,” ACS Nano6(1), 74–80 (2012).
[CrossRef] [PubMed]

Khotkevich, V. V.

K. S. Novoselov, D. Jiang, F. Schedin, T. J. Booth, V. V. Khotkevich, S. V. Morozov, and A. K. Geim, “Two-dimensional atomic crystals,” Proc. Natl. Acad. Sci. U.S.A.102(30), 10451–10453 (2005).
[CrossRef] [PubMed]

Kim, H.

H. S. Lee, S. W. Min, Y. G. Chang, M. K. Park, T. Nam, H. Kim, J. H. Kim, S. Ryu, and S. Im, “MoS₂ nanosheet phototransistors with thickness-modulated optical energy gap,” Nano Lett.12(7), 3695–3700 (2012).
[CrossRef] [PubMed]

Kim, I. G.

W. S. Yun, S. Han, S. C. Hong, I. G. Kim, and J. Lee, “Thickness and strain effects on electronic structures of transition metal dichalcogenides: 2H-MX2 semiconductors (M = Mo, W; X = S, Se, Te),” Phys. Rev. B85(3), 033305 (2012).
[CrossRef]

Kim, J.

A. Splendiani, L. Sun, Y. Zhang, T. Li, J. Kim, C. Y. Chim, G. Galli, and F. Wang, “Emerging photoluminescence in monolayer MoS2.,” Nano Lett.10(4), 1271–1275 (2010).
[CrossRef] [PubMed]

Kim, J. H.

H. S. Lee, S. W. Min, Y. G. Chang, M. K. Park, T. Nam, H. Kim, J. H. Kim, S. Ryu, and S. Im, “MoS₂ nanosheet phototransistors with thickness-modulated optical energy gap,” Nano Lett.12(7), 3695–3700 (2012).
[CrossRef] [PubMed]

Kis, A.

B. Radisavljevic, A. Radenovic, J. Brivio, V. Giacometti, and A. Kis, “Single-layer MoS2 transistors,” Nat. Nanotechnol.6(3), 147–150 (2011).
[CrossRef] [PubMed]

M. M. Benameur, B. Radisavljevic, J. S. Héron, S. Sahoo, H. Berger, and A. Kis, “Visibility of dichalcogenide nanolayers,” Nanotechnology22(12), 125706 (2011).
[CrossRef] [PubMed]

Kloc, C.

V. Podzorov, M. E. Gershenson, C. Kloc, R. Zeis, and E. Bucher, “High-mobility field-effect transistors based on transition metal dichalcogenides,” Appl. Phys. Lett.84(17), 3301–3304 (2004).
[CrossRef]

Korn, T.

G. Plechinger, F. X. Schrettenbrunner, J. Eroms, D. Weiss, C. Schüller, and T. Korn, “Low-temperature photoluminescence of oxide-covered single-layer MoS2,” Phys. Status Solidi (RRL)6(3), 126–128 (2012).
[CrossRef]

T. Korn, S. Heydrich, M. Hirmer, J. Schmutzler, and C. Schüller, “Low-temperature photocarrier dynamics in monolayer MoS2,” Appl. Phys. Lett.99(10), 102109 (2011).
[CrossRef]

Kuc, A.

A. Kuc, N. Zibouche, and T. Heine, “Influence of quantum confinement on the electronic structure of the transition metal sulfide TS2,” Phys. Rev. B83(24), 245213 (2011).
[CrossRef]

Lee, C.

C. Lee, H. Yan, L. E. Brus, T. F. Heinz, J. Hone, and S. Ryu, “Anomalous lattice vibrations of single- and few-layer MoS2.,” ACS Nano4(5), 2695–2700 (2010).
[CrossRef] [PubMed]

K. F. Mak, C. Lee, J. Hone, J. Shan, and T. F. Heinz, “Atomically thin MoS₂: a new direct-gap semiconductor,” Phys. Rev. Lett.105(13), 136805 (2010).
[CrossRef] [PubMed]

Lee, H. S.

H. S. Lee, S. W. Min, Y. G. Chang, M. K. Park, T. Nam, H. Kim, J. H. Kim, S. Ryu, and S. Im, “MoS₂ nanosheet phototransistors with thickness-modulated optical energy gap,” Nano Lett.12(7), 3695–3700 (2012).
[CrossRef] [PubMed]

Lee, J.

W. S. Yun, S. Han, S. C. Hong, I. G. Kim, and J. Lee, “Thickness and strain effects on electronic structures of transition metal dichalcogenides: 2H-MX2 semiconductors (M = Mo, W; X = S, Se, Te),” Phys. Rev. B85(3), 033305 (2012).
[CrossRef]

Levy, F.

T. J. Wieting, A. Grisel, and F. Levy, “Interlayer bonding and localized charge in MoSe2 and α-MoTe2,” Physica B+C99(1-4), 337–342 (1980).
[CrossRef]

Li, H.

H. Li, Q. Zhang, C. C. R. Yap, B. K. Tay, T. H. T. Edwin, A. Olivier, and D. Baillargeat, “From bulk to monolayer MoS2: evolution of Raman scattering,” Adv. Funct. Mater.22(7), 1385–1390 (2012).
[CrossRef]

Z. Yin, H. Li, H. Li, L. Jiang, Y. Shi, Y. Sun, G. Lu, Q. Zhang, X. Chen, and H. Zhang, “Single-layer MoS2 phototransistors,” ACS Nano6(1), 74–80 (2012).
[CrossRef] [PubMed]

Z. Yin, H. Li, H. Li, L. Jiang, Y. Shi, Y. Sun, G. Lu, Q. Zhang, X. Chen, and H. Zhang, “Single-layer MoS2 phototransistors,” ACS Nano6(1), 74–80 (2012).
[CrossRef] [PubMed]

Li, J.

S. Tongay, J. Zhou, C. Ataca, K. Lo, T. S. Matthews, J. Li, J. C. Grossman, and J. Wu, “Thermally driven crossover from indirect toward direct bandgap in 2D semiconductors: MoSe2 versus MoS2.,” Nano Lett.12(11), 5576–5580 (2012).
[CrossRef] [PubMed]

Li, T.

A. Splendiani, L. Sun, Y. Zhang, T. Li, J. Kim, C. Y. Chim, G. Galli, and F. Wang, “Emerging photoluminescence in monolayer MoS2.,” Nano Lett.10(4), 1271–1275 (2010).
[CrossRef] [PubMed]

Liang, W. Y.

A. R. Beal, W. Y. Liang, and H. P. Hughes, “Kramers-Kronig analysis of the reflectivity spectra of 3R-WS2 and 2H-WSe2,” J. Phys.C, 9, 2449–2457 (1976).

Lo, K.

S. Tongay, J. Zhou, C. Ataca, K. Lo, T. S. Matthews, J. Li, J. C. Grossman, and J. Wu, “Thermally driven crossover from indirect toward direct bandgap in 2D semiconductors: MoSe2 versus MoS2.,” Nano Lett.12(11), 5576–5580 (2012).
[CrossRef] [PubMed]

Lohmann, T.

J. Martin, N. Akerman, G. Ulbricht, T. Lohmann, J. H. Smet, K. von Klitzing, and A. Yacoby, “Observation of electron–hole puddles in graphene using a scanning single-electron transistor,” Nat. Phys.4(2), 144–148 (2008).
[CrossRef]

Lu, G.

Z. Yin, H. Li, H. Li, L. Jiang, Y. Shi, Y. Sun, G. Lu, Q. Zhang, X. Chen, and H. Zhang, “Single-layer MoS2 phototransistors,” ACS Nano6(1), 74–80 (2012).
[CrossRef] [PubMed]

Lu, J.

Y. Ma, Y. Dai, M. Guo, C. Niu, J. Lu, and B. Huang, “Electronic and magnetic properties of perfect, vacancy-doped, and nonmetal adsorbed MoSe2, MoTe2 and WS2 monolayers,” Phys. Chem. Chem. Phys.13(34), 15546–15553 (2011).
[CrossRef] [PubMed]

Lux-Steiner, M.

R. Späh, U. Elrod, M. Lux-Steiner, E. Bucher, and S. Wagner, “pn junctions in tungsten diselenide,” Appl. Phys. Lett.43(1), 79–81 (1983).
[CrossRef]

Ma, Y.

Y. Ma, Y. Dai, M. Guo, C. Niu, J. Lu, and B. Huang, “Electronic and magnetic properties of perfect, vacancy-doped, and nonmetal adsorbed MoSe2, MoTe2 and WS2 monolayers,” Phys. Chem. Chem. Phys.13(34), 15546–15553 (2011).
[CrossRef] [PubMed]

Mak, K. F.

K. F. Mak, C. Lee, J. Hone, J. Shan, and T. F. Heinz, “Atomically thin MoS₂: a new direct-gap semiconductor,” Phys. Rev. Lett.105(13), 136805 (2010).
[CrossRef] [PubMed]

Martin, J.

J. Martin, N. Akerman, G. Ulbricht, T. Lohmann, J. H. Smet, K. von Klitzing, and A. Yacoby, “Observation of electron–hole puddles in graphene using a scanning single-electron transistor,” Nat. Phys.4(2), 144–148 (2008).
[CrossRef]

Matsuura, E.

T. Sekine, M. Izumi, T. Nakashizu, K. Uchinokura, and E. Matsuura, “Raman scattering and infrared reflectance in 2H-MoSe2,” J. Phys. Soc. Jpn.49(3), 1069–1077 (1980).
[CrossRef]

Matte, H. S. S. R.

H. S. S. R. Matte, B. Plowman, R. Datta, and C. N. R. Rao, “Graphene analogues of layered metal selenides,” Dalton Trans.40(40), 10322–10325 (2011).
[CrossRef] [PubMed]

Matthews, M.

G. Frey, R. Tenne, M. Matthews, M. Dresselhaus, and G. Dresselhaus, “Raman and resonance Raman investigation of MoS2 nanoparticles,” Phys. Rev. B60(4), 2883–2892 (1999).
[CrossRef]

Matthews, T. S.

S. Tongay, J. Zhou, C. Ataca, K. Lo, T. S. Matthews, J. Li, J. C. Grossman, and J. Wu, “Thermally driven crossover from indirect toward direct bandgap in 2D semiconductors: MoSe2 versus MoS2.,” Nano Lett.12(11), 5576–5580 (2012).
[CrossRef] [PubMed]

Mead, D. G.

D. G. Mead and J. C. Irwin, “Long wavelength optic phonons in WSe2,” Can. J. Phys.55(5), 379–382 (1977).
[CrossRef]

Min, S. W.

H. S. Lee, S. W. Min, Y. G. Chang, M. K. Park, T. Nam, H. Kim, J. H. Kim, S. Ryu, and S. Im, “MoS₂ nanosheet phototransistors with thickness-modulated optical energy gap,” Nano Lett.12(7), 3695–3700 (2012).
[CrossRef] [PubMed]

Molina-Sánchez, A.

A. Molina-Sánchez and L. Wirtz, “Phonons in single-layer and few-layer MoS2 and WS2,” Phys. Rev. B84(15), 155413 (2011).
[CrossRef]

Morozov, S. V.

K. S. Novoselov, D. Jiang, F. Schedin, T. J. Booth, V. V. Khotkevich, S. V. Morozov, and A. K. Geim, “Two-dimensional atomic crystals,” Proc. Natl. Acad. Sci. U.S.A.102(30), 10451–10453 (2005).
[CrossRef] [PubMed]

Nakashizu, T.

T. Sekine, M. Izumi, T. Nakashizu, K. Uchinokura, and E. Matsuura, “Raman scattering and infrared reflectance in 2H-MoSe2,” J. Phys. Soc. Jpn.49(3), 1069–1077 (1980).
[CrossRef]

Nam, T.

H. S. Lee, S. W. Min, Y. G. Chang, M. K. Park, T. Nam, H. Kim, J. H. Kim, S. Ryu, and S. Im, “MoS₂ nanosheet phototransistors with thickness-modulated optical energy gap,” Nano Lett.12(7), 3695–3700 (2012).
[CrossRef] [PubMed]

Ni, J.

Y. Ding, Y. Wang, J. Ni, L. Shi, S. Shi, and W. Tang, “First principles study of structural, vibrational and electronic properties of graphene-like MX2 (M=Mo, Nb, W, Ta; X=S, Se, Te) monolayers,” Physica B406(11), 2254–2260 (2011).
[CrossRef]

Niu, C.

Y. Ma, Y. Dai, M. Guo, C. Niu, J. Lu, and B. Huang, “Electronic and magnetic properties of perfect, vacancy-doped, and nonmetal adsorbed MoSe2, MoTe2 and WS2 monolayers,” Phys. Chem. Chem. Phys.13(34), 15546–15553 (2011).
[CrossRef] [PubMed]

Novoselov, K. S.

K. S. Novoselov, D. Jiang, F. Schedin, T. J. Booth, V. V. Khotkevich, S. V. Morozov, and A. K. Geim, “Two-dimensional atomic crystals,” Proc. Natl. Acad. Sci. U.S.A.102(30), 10451–10453 (2005).
[CrossRef] [PubMed]

Olivier, A.

H. Li, Q. Zhang, C. C. R. Yap, B. K. Tay, T. H. T. Edwin, A. Olivier, and D. Baillargeat, “From bulk to monolayer MoS2: evolution of Raman scattering,” Adv. Funct. Mater.22(7), 1385–1390 (2012).
[CrossRef]

Park, M. K.

H. S. Lee, S. W. Min, Y. G. Chang, M. K. Park, T. Nam, H. Kim, J. H. Kim, S. Ryu, and S. Im, “MoS₂ nanosheet phototransistors with thickness-modulated optical energy gap,” Nano Lett.12(7), 3695–3700 (2012).
[CrossRef] [PubMed]

Plechinger, G.

G. Plechinger, F. X. Schrettenbrunner, J. Eroms, D. Weiss, C. Schüller, and T. Korn, “Low-temperature photoluminescence of oxide-covered single-layer MoS2,” Phys. Status Solidi (RRL)6(3), 126–128 (2012).
[CrossRef]

Plowman, B.

H. S. S. R. Matte, B. Plowman, R. Datta, and C. N. R. Rao, “Graphene analogues of layered metal selenides,” Dalton Trans.40(40), 10322–10325 (2011).
[CrossRef] [PubMed]

Podzorov, V.

V. Podzorov, M. E. Gershenson, C. Kloc, R. Zeis, and E. Bucher, “High-mobility field-effect transistors based on transition metal dichalcogenides,” Appl. Phys. Lett.84(17), 3301–3304 (2004).
[CrossRef]

Radenovic, A.

B. Radisavljevic, A. Radenovic, J. Brivio, V. Giacometti, and A. Kis, “Single-layer MoS2 transistors,” Nat. Nanotechnol.6(3), 147–150 (2011).
[CrossRef] [PubMed]

Radisavljevic, B.

B. Radisavljevic, A. Radenovic, J. Brivio, V. Giacometti, and A. Kis, “Single-layer MoS2 transistors,” Nat. Nanotechnol.6(3), 147–150 (2011).
[CrossRef] [PubMed]

M. M. Benameur, B. Radisavljevic, J. S. Héron, S. Sahoo, H. Berger, and A. Kis, “Visibility of dichalcogenide nanolayers,” Nanotechnology22(12), 125706 (2011).
[CrossRef] [PubMed]

Rao, C. N. R.

H. S. S. R. Matte, B. Plowman, R. Datta, and C. N. R. Rao, “Graphene analogues of layered metal selenides,” Dalton Trans.40(40), 10322–10325 (2011).
[CrossRef] [PubMed]

Rubio-Bollinger, G.

A. Castellanos-Gomez, N. Agraït, and G. Rubio-Bollinger, “Optical identification of atomically thin dichalcogenide crystals,” Appl. Phys. Lett.96(21), 213116 (2010).
[CrossRef]

Ryu, S.

H. S. Lee, S. W. Min, Y. G. Chang, M. K. Park, T. Nam, H. Kim, J. H. Kim, S. Ryu, and S. Im, “MoS₂ nanosheet phototransistors with thickness-modulated optical energy gap,” Nano Lett.12(7), 3695–3700 (2012).
[CrossRef] [PubMed]

C. Lee, H. Yan, L. E. Brus, T. F. Heinz, J. Hone, and S. Ryu, “Anomalous lattice vibrations of single- and few-layer MoS2.,” ACS Nano4(5), 2695–2700 (2010).
[CrossRef] [PubMed]

Sahoo, S.

M. M. Benameur, B. Radisavljevic, J. S. Héron, S. Sahoo, H. Berger, and A. Kis, “Visibility of dichalcogenide nanolayers,” Nanotechnology22(12), 125706 (2011).
[CrossRef] [PubMed]

Schedin, F.

K. S. Novoselov, D. Jiang, F. Schedin, T. J. Booth, V. V. Khotkevich, S. V. Morozov, and A. K. Geim, “Two-dimensional atomic crystals,” Proc. Natl. Acad. Sci. U.S.A.102(30), 10451–10453 (2005).
[CrossRef] [PubMed]

Schmutzler, J.

T. Korn, S. Heydrich, M. Hirmer, J. Schmutzler, and C. Schüller, “Low-temperature photocarrier dynamics in monolayer MoS2,” Appl. Phys. Lett.99(10), 102109 (2011).
[CrossRef]

Schrettenbrunner, F. X.

G. Plechinger, F. X. Schrettenbrunner, J. Eroms, D. Weiss, C. Schüller, and T. Korn, “Low-temperature photoluminescence of oxide-covered single-layer MoS2,” Phys. Status Solidi (RRL)6(3), 126–128 (2012).
[CrossRef]

Schüller, C.

G. Plechinger, F. X. Schrettenbrunner, J. Eroms, D. Weiss, C. Schüller, and T. Korn, “Low-temperature photoluminescence of oxide-covered single-layer MoS2,” Phys. Status Solidi (RRL)6(3), 126–128 (2012).
[CrossRef]

T. Korn, S. Heydrich, M. Hirmer, J. Schmutzler, and C. Schüller, “Low-temperature photocarrier dynamics in monolayer MoS2,” Appl. Phys. Lett.99(10), 102109 (2011).
[CrossRef]

Sekine, T.

T. Sekine, M. Izumi, T. Nakashizu, K. Uchinokura, and E. Matsuura, “Raman scattering and infrared reflectance in 2H-MoSe2,” J. Phys. Soc. Jpn.49(3), 1069–1077 (1980).
[CrossRef]

Shan, J.

K. F. Mak, C. Lee, J. Hone, J. Shan, and T. F. Heinz, “Atomically thin MoS₂: a new direct-gap semiconductor,” Phys. Rev. Lett.105(13), 136805 (2010).
[CrossRef] [PubMed]

Shi, L.

Y. Ding, Y. Wang, J. Ni, L. Shi, S. Shi, and W. Tang, “First principles study of structural, vibrational and electronic properties of graphene-like MX2 (M=Mo, Nb, W, Ta; X=S, Se, Te) monolayers,” Physica B406(11), 2254–2260 (2011).
[CrossRef]

Shi, S.

Y. Ding, Y. Wang, J. Ni, L. Shi, S. Shi, and W. Tang, “First principles study of structural, vibrational and electronic properties of graphene-like MX2 (M=Mo, Nb, W, Ta; X=S, Se, Te) monolayers,” Physica B406(11), 2254–2260 (2011).
[CrossRef]

Shi, Y.

Z. Yin, H. Li, H. Li, L. Jiang, Y. Shi, Y. Sun, G. Lu, Q. Zhang, X. Chen, and H. Zhang, “Single-layer MoS2 phototransistors,” ACS Nano6(1), 74–80 (2012).
[CrossRef] [PubMed]

Smet, J. H.

J. Martin, N. Akerman, G. Ulbricht, T. Lohmann, J. H. Smet, K. von Klitzing, and A. Yacoby, “Observation of electron–hole puddles in graphene using a scanning single-electron transistor,” Nat. Phys.4(2), 144–148 (2008).
[CrossRef]

Solanki, G. K.

M. P. Deshpande, G. K. Solanki, and M. K. Agarwal, “Optical band gap in tungsten diselenide single crystals intercalated by indium,” Mater. Lett.43(1-2), 66–72 (2000).
[CrossRef]

Späh, R.

R. Späh, U. Elrod, M. Lux-Steiner, E. Bucher, and S. Wagner, “pn junctions in tungsten diselenide,” Appl. Phys. Lett.43(1), 79–81 (1983).
[CrossRef]

Splendiani, A.

A. Splendiani, L. Sun, Y. Zhang, T. Li, J. Kim, C. Y. Chim, G. Galli, and F. Wang, “Emerging photoluminescence in monolayer MoS2.,” Nano Lett.10(4), 1271–1275 (2010).
[CrossRef] [PubMed]

Sugai, S.

S. Sugai and T. Ueda, “High-pressure Raman spectroscopy in the layered materials 2H-MoS2, 2H-MoSe2, and 2H-MoTe2,” Phys. Rev. B26(12), 6554–6558 (1982).
[CrossRef]

Sun, L.

A. Splendiani, L. Sun, Y. Zhang, T. Li, J. Kim, C. Y. Chim, G. Galli, and F. Wang, “Emerging photoluminescence in monolayer MoS2.,” Nano Lett.10(4), 1271–1275 (2010).
[CrossRef] [PubMed]

Sun, Y.

Z. Yin, H. Li, H. Li, L. Jiang, Y. Shi, Y. Sun, G. Lu, Q. Zhang, X. Chen, and H. Zhang, “Single-layer MoS2 phototransistors,” ACS Nano6(1), 74–80 (2012).
[CrossRef] [PubMed]

Takahashi, T.

H. Fang, S. Chuang, T. C. Chang, K. Takei, T. Takahashi, and A. Javey, “High-performance single layered WSe₂ p-FETs with chemically doped contacts,” Nano Lett.12(7), 3788–3792 (2012).
[CrossRef] [PubMed]

Takei, K.

H. Fang, S. Chuang, T. C. Chang, K. Takei, T. Takahashi, and A. Javey, “High-performance single layered WSe₂ p-FETs with chemically doped contacts,” Nano Lett.12(7), 3788–3792 (2012).
[CrossRef] [PubMed]

Tang, W.

Y. Ding, Y. Wang, J. Ni, L. Shi, S. Shi, and W. Tang, “First principles study of structural, vibrational and electronic properties of graphene-like MX2 (M=Mo, Nb, W, Ta; X=S, Se, Te) monolayers,” Physica B406(11), 2254–2260 (2011).
[CrossRef]

Tay, B. K.

H. Li, Q. Zhang, C. C. R. Yap, B. K. Tay, T. H. T. Edwin, A. Olivier, and D. Baillargeat, “From bulk to monolayer MoS2: evolution of Raman scattering,” Adv. Funct. Mater.22(7), 1385–1390 (2012).
[CrossRef]

Tenne, R.

G. Frey, R. Tenne, M. Matthews, M. Dresselhaus, and G. Dresselhaus, “Raman and resonance Raman investigation of MoS2 nanoparticles,” Phys. Rev. B60(4), 2883–2892 (1999).
[CrossRef]

Tongay, S.

S. Tongay, J. Zhou, C. Ataca, K. Lo, T. S. Matthews, J. Li, J. C. Grossman, and J. Wu, “Thermally driven crossover from indirect toward direct bandgap in 2D semiconductors: MoSe2 versus MoS2.,” Nano Lett.12(11), 5576–5580 (2012).
[CrossRef] [PubMed]

Topsakal, M.

C. Ataca, M. Topsakal, E. Aktürk, and S. Ciraci, “A comparative study of lattice dynamics of three- and two-dimensional MoS2,” J. Phys. Chem. C115(33), 16354–16361 (2011).
[CrossRef]

Uchinokura, K.

T. Sekine, M. Izumi, T. Nakashizu, K. Uchinokura, and E. Matsuura, “Raman scattering and infrared reflectance in 2H-MoSe2,” J. Phys. Soc. Jpn.49(3), 1069–1077 (1980).
[CrossRef]

Ueda, T.

S. Sugai and T. Ueda, “High-pressure Raman spectroscopy in the layered materials 2H-MoS2, 2H-MoSe2, and 2H-MoTe2,” Phys. Rev. B26(12), 6554–6558 (1982).
[CrossRef]

Ulbricht, G.

J. Martin, N. Akerman, G. Ulbricht, T. Lohmann, J. H. Smet, K. von Klitzing, and A. Yacoby, “Observation of electron–hole puddles in graphene using a scanning single-electron transistor,” Nat. Phys.4(2), 144–148 (2008).
[CrossRef]

Verble, J.

T. Wieting and J. Verble, “Infrared and Raman studies of long-wavelength optical phonons in hexagonal MoS2,” Phys. Rev. B3(12), 4286–4292 (1971).
[CrossRef]

J. Verble and T. Wieting, “Lattice mode degeneracy in MoS2 and other layer compounds,” Phys. Rev. Lett.25(6), 362–365 (1970).
[CrossRef]

von Klitzing, K.

J. Martin, N. Akerman, G. Ulbricht, T. Lohmann, J. H. Smet, K. von Klitzing, and A. Yacoby, “Observation of electron–hole puddles in graphene using a scanning single-electron transistor,” Nat. Phys.4(2), 144–148 (2008).
[CrossRef]

Wagner, S.

R. Späh, U. Elrod, M. Lux-Steiner, E. Bucher, and S. Wagner, “pn junctions in tungsten diselenide,” Appl. Phys. Lett.43(1), 79–81 (1983).
[CrossRef]

Wang, F.

A. Splendiani, L. Sun, Y. Zhang, T. Li, J. Kim, C. Y. Chim, G. Galli, and F. Wang, “Emerging photoluminescence in monolayer MoS2.,” Nano Lett.10(4), 1271–1275 (2010).
[CrossRef] [PubMed]

Wang, Y.

Y. Ding, Y. Wang, J. Ni, L. Shi, S. Shi, and W. Tang, “First principles study of structural, vibrational and electronic properties of graphene-like MX2 (M=Mo, Nb, W, Ta; X=S, Se, Te) monolayers,” Physica B406(11), 2254–2260 (2011).
[CrossRef]

Weiss, D.

G. Plechinger, F. X. Schrettenbrunner, J. Eroms, D. Weiss, C. Schüller, and T. Korn, “Low-temperature photoluminescence of oxide-covered single-layer MoS2,” Phys. Status Solidi (RRL)6(3), 126–128 (2012).
[CrossRef]

Wieting, T.

T. Wieting and J. Verble, “Infrared and Raman studies of long-wavelength optical phonons in hexagonal MoS2,” Phys. Rev. B3(12), 4286–4292 (1971).
[CrossRef]

J. Verble and T. Wieting, “Lattice mode degeneracy in MoS2 and other layer compounds,” Phys. Rev. Lett.25(6), 362–365 (1970).
[CrossRef]

Wieting, T. J.

T. J. Wieting, A. Grisel, and F. Levy, “Interlayer bonding and localized charge in MoSe2 and α-MoTe2,” Physica B+C99(1-4), 337–342 (1980).
[CrossRef]

Wilson, J. A.

J. A. Wilson and A. D. Yoffe, “The transition metal dichalcogenides discussion and interpretation of the observed optical, electrical and structural properties,” Adv. Phys.18(73), 193–335 (1969).
[CrossRef]

Wirtz, L.

A. Molina-Sánchez and L. Wirtz, “Phonons in single-layer and few-layer MoS2 and WS2,” Phys. Rev. B84(15), 155413 (2011).
[CrossRef]

Wu, J.

S. Tongay, J. Zhou, C. Ataca, K. Lo, T. S. Matthews, J. Li, J. C. Grossman, and J. Wu, “Thermally driven crossover from indirect toward direct bandgap in 2D semiconductors: MoSe2 versus MoS2.,” Nano Lett.12(11), 5576–5580 (2012).
[CrossRef] [PubMed]

Yacoby, A.

J. Martin, N. Akerman, G. Ulbricht, T. Lohmann, J. H. Smet, K. von Klitzing, and A. Yacoby, “Observation of electron–hole puddles in graphene using a scanning single-electron transistor,” Nat. Phys.4(2), 144–148 (2008).
[CrossRef]

Yan, H.

C. Lee, H. Yan, L. E. Brus, T. F. Heinz, J. Hone, and S. Ryu, “Anomalous lattice vibrations of single- and few-layer MoS2.,” ACS Nano4(5), 2695–2700 (2010).
[CrossRef] [PubMed]

Yang, D.

R. Gordon, D. Yang, E. Crozier, D. Jiang, and R. Frindt, “Structures of exfoliated single layers of WS2, MoS2, and MoSe2 in aqueous suspension,” Phys. Rev. B65(12), 125407 (2002).
[CrossRef]

Yap, C. C. R.

H. Li, Q. Zhang, C. C. R. Yap, B. K. Tay, T. H. T. Edwin, A. Olivier, and D. Baillargeat, “From bulk to monolayer MoS2: evolution of Raman scattering,” Adv. Funct. Mater.22(7), 1385–1390 (2012).
[CrossRef]

Yin, Z.

Z. Yin, H. Li, H. Li, L. Jiang, Y. Shi, Y. Sun, G. Lu, Q. Zhang, X. Chen, and H. Zhang, “Single-layer MoS2 phototransistors,” ACS Nano6(1), 74–80 (2012).
[CrossRef] [PubMed]

Yoffe, A. D.

J. A. Wilson and A. D. Yoffe, “The transition metal dichalcogenides discussion and interpretation of the observed optical, electrical and structural properties,” Adv. Phys.18(73), 193–335 (1969).
[CrossRef]

Yun, W. S.

W. S. Yun, S. Han, S. C. Hong, I. G. Kim, and J. Lee, “Thickness and strain effects on electronic structures of transition metal dichalcogenides: 2H-MX2 semiconductors (M = Mo, W; X = S, Se, Te),” Phys. Rev. B85(3), 033305 (2012).
[CrossRef]

Zeis, R.

V. Podzorov, M. E. Gershenson, C. Kloc, R. Zeis, and E. Bucher, “High-mobility field-effect transistors based on transition metal dichalcogenides,” Appl. Phys. Lett.84(17), 3301–3304 (2004).
[CrossRef]

Zhang, H.

Z. Yin, H. Li, H. Li, L. Jiang, Y. Shi, Y. Sun, G. Lu, Q. Zhang, X. Chen, and H. Zhang, “Single-layer MoS2 phototransistors,” ACS Nano6(1), 74–80 (2012).
[CrossRef] [PubMed]

Zhang, Q.

Z. Yin, H. Li, H. Li, L. Jiang, Y. Shi, Y. Sun, G. Lu, Q. Zhang, X. Chen, and H. Zhang, “Single-layer MoS2 phototransistors,” ACS Nano6(1), 74–80 (2012).
[CrossRef] [PubMed]

H. Li, Q. Zhang, C. C. R. Yap, B. K. Tay, T. H. T. Edwin, A. Olivier, and D. Baillargeat, “From bulk to monolayer MoS2: evolution of Raman scattering,” Adv. Funct. Mater.22(7), 1385–1390 (2012).
[CrossRef]

Zhang, Y.

A. Splendiani, L. Sun, Y. Zhang, T. Li, J. Kim, C. Y. Chim, G. Galli, and F. Wang, “Emerging photoluminescence in monolayer MoS2.,” Nano Lett.10(4), 1271–1275 (2010).
[CrossRef] [PubMed]

Zhou, J.

S. Tongay, J. Zhou, C. Ataca, K. Lo, T. S. Matthews, J. Li, J. C. Grossman, and J. Wu, “Thermally driven crossover from indirect toward direct bandgap in 2D semiconductors: MoSe2 versus MoS2.,” Nano Lett.12(11), 5576–5580 (2012).
[CrossRef] [PubMed]

Zibouche, N.

A. Kuc, N. Zibouche, and T. Heine, “Influence of quantum confinement on the electronic structure of the transition metal sulfide TS2,” Phys. Rev. B83(24), 245213 (2011).
[CrossRef]

ACS Nano

Z. Yin, H. Li, H. Li, L. Jiang, Y. Shi, Y. Sun, G. Lu, Q. Zhang, X. Chen, and H. Zhang, “Single-layer MoS2 phototransistors,” ACS Nano6(1), 74–80 (2012).
[CrossRef] [PubMed]

C. Lee, H. Yan, L. E. Brus, T. F. Heinz, J. Hone, and S. Ryu, “Anomalous lattice vibrations of single- and few-layer MoS2.,” ACS Nano4(5), 2695–2700 (2010).
[CrossRef] [PubMed]

Adv. Funct. Mater.

H. Li, Q. Zhang, C. C. R. Yap, B. K. Tay, T. H. T. Edwin, A. Olivier, and D. Baillargeat, “From bulk to monolayer MoS2: evolution of Raman scattering,” Adv. Funct. Mater.22(7), 1385–1390 (2012).
[CrossRef]

Adv. Phys.

J. A. Wilson and A. D. Yoffe, “The transition metal dichalcogenides discussion and interpretation of the observed optical, electrical and structural properties,” Adv. Phys.18(73), 193–335 (1969).
[CrossRef]

Appl. Phys. Lett.

T. Korn, S. Heydrich, M. Hirmer, J. Schmutzler, and C. Schüller, “Low-temperature photocarrier dynamics in monolayer MoS2,” Appl. Phys. Lett.99(10), 102109 (2011).
[CrossRef]

V. Podzorov, M. E. Gershenson, C. Kloc, R. Zeis, and E. Bucher, “High-mobility field-effect transistors based on transition metal dichalcogenides,” Appl. Phys. Lett.84(17), 3301–3304 (2004).
[CrossRef]

R. Späh, U. Elrod, M. Lux-Steiner, E. Bucher, and S. Wagner, “pn junctions in tungsten diselenide,” Appl. Phys. Lett.43(1), 79–81 (1983).
[CrossRef]

A. Castellanos-Gomez, N. Agraït, and G. Rubio-Bollinger, “Optical identification of atomically thin dichalcogenide crystals,” Appl. Phys. Lett.96(21), 213116 (2010).
[CrossRef]

Can. J. Phys.

D. G. Mead and J. C. Irwin, “Long wavelength optic phonons in WSe2,” Can. J. Phys.55(5), 379–382 (1977).
[CrossRef]

Dalton Trans.

H. S. S. R. Matte, B. Plowman, R. Datta, and C. N. R. Rao, “Graphene analogues of layered metal selenides,” Dalton Trans.40(40), 10322–10325 (2011).
[CrossRef] [PubMed]

J. Phys.

A. R. Beal, W. Y. Liang, and H. P. Hughes, “Kramers-Kronig analysis of the reflectivity spectra of 3R-WS2 and 2H-WSe2,” J. Phys.C, 9, 2449–2457 (1976).

J. Phys. Chem.

A. R. Beal and H. P. Hughes, “Kramers-Kronig analysis of the reflectivity spectra of 2H-MoS2, 2H-MoSe2 and 2H-MoTe2,” J. Phys. Chem.12, 881–890 (1979).

J. Phys. Chem. C

C. Ataca, M. Topsakal, E. Aktürk, and S. Ciraci, “A comparative study of lattice dynamics of three- and two-dimensional MoS2,” J. Phys. Chem. C115(33), 16354–16361 (2011).
[CrossRef]

J. Phys. Chem. Solids

A. Anedda and E. Fortin, “Exciton spectra in MoSe2,” J. Phys. Chem. Solids41(8), 865–869 (1980).
[CrossRef]

J. Phys. Soc. Jpn.

T. Sekine, M. Izumi, T. Nakashizu, K. Uchinokura, and E. Matsuura, “Raman scattering and infrared reflectance in 2H-MoSe2,” J. Phys. Soc. Jpn.49(3), 1069–1077 (1980).
[CrossRef]

Mater. Lett.

M. P. Deshpande, G. K. Solanki, and M. K. Agarwal, “Optical band gap in tungsten diselenide single crystals intercalated by indium,” Mater. Lett.43(1-2), 66–72 (2000).
[CrossRef]

Nano Lett.

A. Splendiani, L. Sun, Y. Zhang, T. Li, J. Kim, C. Y. Chim, G. Galli, and F. Wang, “Emerging photoluminescence in monolayer MoS2.,” Nano Lett.10(4), 1271–1275 (2010).
[CrossRef] [PubMed]

H. Fang, S. Chuang, T. C. Chang, K. Takei, T. Takahashi, and A. Javey, “High-performance single layered WSe₂ p-FETs with chemically doped contacts,” Nano Lett.12(7), 3788–3792 (2012).
[CrossRef] [PubMed]

H. S. Lee, S. W. Min, Y. G. Chang, M. K. Park, T. Nam, H. Kim, J. H. Kim, S. Ryu, and S. Im, “MoS₂ nanosheet phototransistors with thickness-modulated optical energy gap,” Nano Lett.12(7), 3695–3700 (2012).
[CrossRef] [PubMed]

S. Tongay, J. Zhou, C. Ataca, K. Lo, T. S. Matthews, J. Li, J. C. Grossman, and J. Wu, “Thermally driven crossover from indirect toward direct bandgap in 2D semiconductors: MoSe2 versus MoS2.,” Nano Lett.12(11), 5576–5580 (2012).
[CrossRef] [PubMed]

Nanotechnology

M. M. Benameur, B. Radisavljevic, J. S. Héron, S. Sahoo, H. Berger, and A. Kis, “Visibility of dichalcogenide nanolayers,” Nanotechnology22(12), 125706 (2011).
[CrossRef] [PubMed]

Nat. Nanotechnol.

B. Radisavljevic, A. Radenovic, J. Brivio, V. Giacometti, and A. Kis, “Single-layer MoS2 transistors,” Nat. Nanotechnol.6(3), 147–150 (2011).
[CrossRef] [PubMed]

Nat. Phys.

J. Martin, N. Akerman, G. Ulbricht, T. Lohmann, J. H. Smet, K. von Klitzing, and A. Yacoby, “Observation of electron–hole puddles in graphene using a scanning single-electron transistor,” Nat. Phys.4(2), 144–148 (2008).
[CrossRef]

Phys. Chem. Chem. Phys.

Y. Ma, Y. Dai, M. Guo, C. Niu, J. Lu, and B. Huang, “Electronic and magnetic properties of perfect, vacancy-doped, and nonmetal adsorbed MoSe2, MoTe2 and WS2 monolayers,” Phys. Chem. Chem. Phys.13(34), 15546–15553 (2011).
[CrossRef] [PubMed]

Phys. Rev. B

W. S. Yun, S. Han, S. C. Hong, I. G. Kim, and J. Lee, “Thickness and strain effects on electronic structures of transition metal dichalcogenides: 2H-MX2 semiconductors (M = Mo, W; X = S, Se, Te),” Phys. Rev. B85(3), 033305 (2012).
[CrossRef]

S. Sugai and T. Ueda, “High-pressure Raman spectroscopy in the layered materials 2H-MoS2, 2H-MoSe2, and 2H-MoTe2,” Phys. Rev. B26(12), 6554–6558 (1982).
[CrossRef]

A. Molina-Sánchez and L. Wirtz, “Phonons in single-layer and few-layer MoS2 and WS2,” Phys. Rev. B84(15), 155413 (2011).
[CrossRef]

G. Frey, R. Tenne, M. Matthews, M. Dresselhaus, and G. Dresselhaus, “Raman and resonance Raman investigation of MoS2 nanoparticles,” Phys. Rev. B60(4), 2883–2892 (1999).
[CrossRef]

T. Wieting and J. Verble, “Infrared and Raman studies of long-wavelength optical phonons in hexagonal MoS2,” Phys. Rev. B3(12), 4286–4292 (1971).
[CrossRef]

R. Gordon, D. Yang, E. Crozier, D. Jiang, and R. Frindt, “Structures of exfoliated single layers of WS2, MoS2, and MoSe2 in aqueous suspension,” Phys. Rev. B65(12), 125407 (2002).
[CrossRef]

A. Kuc, N. Zibouche, and T. Heine, “Influence of quantum confinement on the electronic structure of the transition metal sulfide TS2,” Phys. Rev. B83(24), 245213 (2011).
[CrossRef]

Phys. Rev. B Condens. Matter

R. Coehoorn, C. Haas, and R. de Groot, “Electronic structure of MoSe2, MoS2, and WSe2. II. The nature of the optical band gaps,” Phys. Rev. B Condens. Matter35(12), 6203–6206 (1987).
[CrossRef] [PubMed]

Phys. Rev. Lett.

K. F. Mak, C. Lee, J. Hone, J. Shan, and T. F. Heinz, “Atomically thin MoS₂: a new direct-gap semiconductor,” Phys. Rev. Lett.105(13), 136805 (2010).
[CrossRef] [PubMed]

J. Verble and T. Wieting, “Lattice mode degeneracy in MoS2 and other layer compounds,” Phys. Rev. Lett.25(6), 362–365 (1970).
[CrossRef]

Phys. Status Solidi (RRL)

G. Plechinger, F. X. Schrettenbrunner, J. Eroms, D. Weiss, C. Schüller, and T. Korn, “Low-temperature photoluminescence of oxide-covered single-layer MoS2,” Phys. Status Solidi (RRL)6(3), 126–128 (2012).
[CrossRef]

Physica B

Y. Ding, Y. Wang, J. Ni, L. Shi, S. Shi, and W. Tang, “First principles study of structural, vibrational and electronic properties of graphene-like MX2 (M=Mo, Nb, W, Ta; X=S, Se, Te) monolayers,” Physica B406(11), 2254–2260 (2011).
[CrossRef]

Physica B+C

T. J. Wieting, A. Grisel, and F. Levy, “Interlayer bonding and localized charge in MoSe2 and α-MoTe2,” Physica B+C99(1-4), 337–342 (1980).
[CrossRef]

Proc. Natl. Acad. Sci. U.S.A.

K. S. Novoselov, D. Jiang, F. Schedin, T. J. Booth, V. V. Khotkevich, S. V. Morozov, and A. K. Geim, “Two-dimensional atomic crystals,” Proc. Natl. Acad. Sci. U.S.A.102(30), 10451–10453 (2005).
[CrossRef] [PubMed]

Science

A. K. Geim, “Graphene: status and prospects,” Science324(5934), 1530–1534 (2009).
[CrossRef] [PubMed]

Other

H. Zeng, G.-B. Liu, J. Dai, Y. Yan, B. Zhu, R. He, L. Xie, S. Xu, X. Chen, W. Yao, and X. Cui, “Optical signature of symmetry variations and spin-valley coupling in atomically thin tungsten dichalcogenides,” arXiv:1208.5864 (2012).

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Figures (7)

Fig. 1
Fig. 1

Mechanically exfoliated WSe2 on a SiO2/Si wafer. (a) Optical micrograph under white light illumination. Few-layers (FL) appear purple next to the bright bulk WSe2. (b) Topography of marked area with height profile along red line, scanned with an atomic force microscope (AFM).

Fig. 2
Fig. 2

Schematic drawing of the four Raman active and two inactive modes of the transition metal dichalcogenides MX2 (M = Mo, W and X = Se, S).

Fig. 3
Fig. 3

Raman spectra of bulk and few-layer MoSe2. Labels ‘1L’ – ‘5L’ indicate the number of layers. Raman spectra are vertically displaced for clarity.

Fig. 4
Fig. 4

Schematic drawing of all Raman active out-of-plane vibrational modes in 1 to 5 layers of MoSe2. Dashed red lines between the layers denote an increase of the mode frequency compared to non-interacting layers. Green dotted lines indicate a decrease of the oscillation frequency. The horizontal dashed line indicates the mirror plane σh of the unit cells with odd number of layers. The black dot marks the center of inversion for the unit cells with even number of layers. Due to a smaller unit cell, the out-of-plane mode for the monolayer is denoted A′1.

Fig. 5
Fig. 5

Raman spectra of bulk and few-layer WSe2. Labels ‘1L’ – ‘5L’ indicate the number of layers. Raman spectra are vertically displaced for clarity.

Fig. 6
Fig. 6

Photoluminescence of monolayer and few-layer MoSe2 (a) and WSe2 (b). Spectra are recorded at room temperature, 532 nm excitation wavelength, and a fluence of 2100 W/cm2 (a) and 250 W/cm2 (b). PL spectra are Fourier-filtered with a 0.05 pixel−1 short pass to remove etaloning due to the back-illuminated CCD camera.

Fig. 7
Fig. 7

Schematic drawing of reflected and transmitted light in the MX2/SiO2/Si multilayer structure for the determination of the absorption in the MX2 monolayer.

Equations (4)

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A MX2 = R 0 R MX2 + T 0 T MX2 ,
r= I refl,MX2 / I refl,substrate = R MX2 / R 0 .
i R = I Raman,MX2 / I Raman,substrate = ( T MX2 / T 0 ) 2 .
A MX2 =1r R 0 (1 R 0 ) i R .

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