Hostname: page-component-586b7cd67f-dlnhk Total loading time: 0 Render date: 2024-11-23T20:09:35.268Z Has data issue: false hasContentIssue false
  • English
  • Français

Two-dimensional layered materials: Structure, properties, and prospects for device applications

Published online by Cambridge University Press:  14 February 2014

Anupama B. Kaul
Anupama B. Kaul*
Affiliation:
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109; and National Science Foundation, Arlington, Virginia 22203
*
a)Address all correspondence to this author. e-mail: [email protected], [email protected]
Get access

Abstract

Graphene's layered structure has opened new prospects for the exploration of properties of other monolayer-thick two-dimensional (2D) layered crystals. The emergence of these inorganic 2D atomic crystals beyond graphene promises a diverse spectrum of properties. For example, hexagonal-boron nitride (h-BN), a layered material closest in structure to graphene is an insulator, while niobium selenide (NbSe2), a transition metal dichalcogenide, is metallic, and monolayers of other transition metal dichalcogenides such as molybdenum disulfide (MoS2) and tungsten disulfide (WS2) are direct band gap semiconductors. The rich spectrum of properties exhibited by these 2D layered material systems can potentially be engineered on-demand and creates exciting prospects for using such systems in device applications ranging from electronics, photonics, energy harvesting, flexible electronics, transparent electrodes, and sensing. A review of the structure, properties, and the emerging device applications of these materials is presented in this paper. While the layered structure of these materials makes them amenable to mechanical exfoliation for quickly unveiling their novel properties and for fabricating proof-of-concept devices, an overview of the synthesis routes that can potentially enable scalable avenues for forming these 2D atomic crystals is also discussed.

Type
Invited Paper
Information
Journal of Materials Research , Volume 29 , Issue 3: Focus Issue: Graphene and Beyond , 14 February 2014 , pp. 348 - 361
Copyright
Copyright © Materials Research Society 2014 

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

Novoselov, K.S., Geim, A.K., Morozov, S.V., Jiang, D., Zhang, Y., Dubonos, S.V., Grigorieva, I.V., and Firsov, A.A.: Electric field effect in atomically thin carbon films. Science 306(5696), 666 (2004).Google Scholar
Lin, Y.M., Dimitrakopoulos, C., Jenkins, K.A., Farmer, D.B., Chiu, H.Y., Grill, A., and Avouris, P.: 100 GHz transistors from wafer-scale epitaxial graphene. Science 327(5966), 662 (2010).CrossRefGoogle ScholarPubMed
Wu, Y.Q., Jenkins, K.A., Valdes-Garcia, A., Farmer, D.B., Zhu, Y., Bol, A.A., Dimitrakopoulos, C., Zhu, W.J., Xia, F.N., Avouris, P., and Lin, Y.M.: State-of-the-art graphene high-frequency electronics. Nano Lett. 12(6), 3062 (2012).CrossRefGoogle ScholarPubMed
Khatami, Y., Li, H., Xu, C., and Banerjee, K.: Metal-to-multilayer-graphene contact – Part 1: Contact resistance modeling. IEEE Trans. Electron Devices 59(9), 2444 (2012).CrossRefGoogle Scholar
Jeong, H.M., Lee, J.W., Shin, W.H., Choi, Y.J., Shin, H.J., Kang, J.K., and Choi, J.W.: Nitrogen-doped graphene for high-performance ultracapacitors and the importance of nitrogen-doped sites at basal planes. Nano Lett. 11(6), 2472 (2011).Google Scholar
Lu, Y., Lerner, M.B., Qi, Z.J., Mitala, J.J., Lim, J.H., Discher, B.M., and Johnson, A.T.C.: Graphene-protein bioelectronics devices with wavelength-dependent photoresponse. Appl. Phys. Lett. 100, 033110 (2012).CrossRefGoogle Scholar
Kim, K.S., Zhao, Y., Jang, H., Lee, S.Y., Kim, J.M., Kim, K.S., Ahn, J.H., Kim, P., Choi, J.Y., and Hong, B.H.: Large-scale pattern growth of graphene films for stretchable transparent electrodes. Nature 457(7230), 706 (2009).CrossRefGoogle ScholarPubMed
Wei, P., Bao, W., Pu, Y., Lau, C.N., and Shi, J.: Anomalous thermoelectric transport of Dirac particles in graphene. Phys. Rev. Lett. 102(16), 166808 (2009).CrossRefGoogle ScholarPubMed
Miao, X., Tongay, S., Petterson, M.K., Berke, K., Rinzler, A.G., Appleton, B.R., and Hebard, A.F.: High efficiency graphene solar cells by chemical doping. Nano Lett. 12(6), 2745 (2012).Google Scholar
Dang, X., Yi, H., Ham, M., Qi, J., Yun, D., Ladewski, R., Strano, M.S., Hammond, P.T., and Belcher, A.M.: Virus-templated self-assembled single-walled carbon nanotubes for highly efficient electron collection in photovoltaic devices. Nat. Nanotechnol. 6(6), 377 (2011).Google Scholar
Vakil, A. and Engheta, N.: Transformation optics using graphene. Science 332(6035), 1291 (2011).Google Scholar
Loh, O.Y. and Espinosa, H.D.: Nanoelectromechanical contact switches. Nat. Nanotechnol. 7(5), 283 (2012).Google Scholar
Li, X., Wang, X., Zhang, L., Lee, S., and Dai, H.: Chemically derived, ultrasmooth graphene nanoribbon semiconductors. Science 319(5867), 1229 (2008).CrossRefGoogle ScholarPubMed
Balog, R., Jorgensen, B., Nilsson, L., Andersen, M., Rienks, E., Bianchi, M., Fanetti, M., Lægsgaard, E., Baraldi, A., Lizzit, S., Sljivancanin, Z., Besenbacher, F., Hammer, B., Pedersen, T.G., Hofmann, P., and Hornekær, L.: Bandgap opening in graphene induced by patterned hydrogen adsorption. Nat. Mater. 9(4), 315 (2010).CrossRefGoogle ScholarPubMed
Zhang, Y.B., Tang, T.T., Girit, C., Hao, Z., Martin, M.C., Zettl, A., Crommie, M.F., Shen, Y.R., and Wang, F.: Direct observation of a widely tunable bandgap in bilayer graphene. Nature 459(7248), 820 (2009).Google Scholar
Novoselov, K., Jiang, D., Schedin, F., Booth, T.J., Khotkevich, V.V., Morozov, S.V.,and Geim, A.K.: Two-dimensional atomic crystals. Proc. Natl. Acad. Sci. U.S.A. 102(30), 10451 (2005).Google Scholar
Wang, Q.H., Kalantar-Zadeh, K., Kis, A., Coleman, J.N., and Strano, M.S.: Electronics and optoelectronics of two-dimensional transition metal dichalcogenides. Nat. Nanotechnol. 7, 699 (2012).CrossRefGoogle ScholarPubMed
Xu, M., Liang, T., Shi, M., and Chen, H.: Graphene-like two-dimensional materials. Chem. Rev. 113, 3766 (2013).CrossRefGoogle ScholarPubMed
Bianco, E., Butler, S., Jiang, S., Restrepo, O.D., Windl, W., and Goldberger, J.E.: Stability and exfoliation of germanane: A germanium graphane analogue. ACS Nano 7(5), 4414–4421 (2013).CrossRefGoogle ScholarPubMed
Vogt, P., Padova, P.D., Quaresima, C., Avila, J., Frantzeskakis, E., Asensio, M.C., Resta, A., Ealet, B., and . Lay, G.L: Silicene: Compelling experimental evidence for graphene like two-dimensional silicon. Phys. Rev. Lett. 108(15), 155501 (2012).CrossRefGoogle Scholar
Song, L., Liu, Z., Reddy, A.L., Narayanan, N.T., Taha-Tijerina, J., Peng, J., Gao, G., Lou, J., Vajtai, R., and Ajayan, P.M.: Binary and ternary atomic layers built from carbon, boron, and nitrogen. Adv. Mater. 24(36), 4878 (2012).Google Scholar
http://nsf2dworkshop.rice.edu/home/.Google Scholar
Wilson, J.A. and Yoffe, A.D.: Transition metal dichalcogenides: Discussion and interpretation of observed optical, electrical and structural properties. Adv. Phys. 18, 193 (1969).CrossRefGoogle Scholar
Osada, M. and Sasaki, T.: Two-dimensional dielectric nanosheets: Novel nanoelectronics from nanocrystal building blocks. Adv. Mater. 24(2), 210 (2012).Google Scholar
Dean, C.R., Young, A.F., Meric, I., Lee, C., Wang, L., Sorgenfrei, S., Watanabe, K., Taniguchi, T., Kim, P., Shepard, K.L., and Hone, J.: Born nitride substrates for high-quality graphene electronics. Nat. Nanotechnol. 5(10), 722 (2010).Google Scholar
Ataca, C., Sahin, H., and Ciraci, S.J.: Stable, single-layer MX2 transition-metal oxides and dichalcogenides in a honeycomb-like structure. Phys. Chem. C 116(16), 8983 (2012).CrossRefGoogle Scholar
Kuc, A., Zibouche, N., and Heine, T.: Influence of quantum confinement on the electronic structure of the transition metal sulfide TS2. Phys. Rev. B 83(24), 245213 (2011).CrossRefGoogle Scholar
Chhowalla, M., Shin, H.S., Eda, G., Li, L-J., Loh, K.P., and Zhang, H.: The chemistry of two-dimensional layered transition metal dichalcogenide nanosheets. Nat. Chem. 5, 263 (2013).Google Scholar
Morosan, E., Zandbergen, H.W., Dennis, B.S., Bos, J.W.G., Onse, Y., Klimczuk, T., Ramirez, A.P., Ong, N.P., and Cava, R.J.: Superconductivity in CuxTiSe2 . Nat. Phys. 2(8), 544 (2006).Google Scholar
Husanikova, P., Fedor, J., Derer, J., Soltys, J., Cambel, V., Iavarone, M., May, S.J., and Karapetrov, G.: Magnetization properties and vortex phase diagram in CuxTiSe2 single crystals. Phys. Rev. B 88(17), 174501 (2013).CrossRefGoogle Scholar
Li, T. and Galli, G.: Electronic properties of MoS2 nanoparticles. J. Phys. Chem. C 111(44), 16192 (2007).CrossRefGoogle Scholar
Zhao, W., Ghorannevis, Z., Chu, L., Toh, M., Kloc, C., Tan, P-H., and Eda, G.: Evolution of electronic structure in atomically thin sheets of WS2 and WSe2 . ACS Nano 7(1), 791 (2013).Google Scholar
Ma, Y.D., Dai, Y., Guo, M., Niu, C.W., Lu, J.B., and Huang, B.B.: Electronic and magnetic properties of perfect, vacancy-doped, and nonmetal adsorbed MoSe2, MoTe2 and WS2 monolayers. Phys. Chem. Chem. Phys. 13(34), 15546 (2011).Google Scholar
Splendiani, A., Sun, L., Zhang, Y.B., Li, T.S., Kim, J., Chim, C. Y., Galli, G., and Wang, F.: Emerging photoluminescence in monolayer MoS2 . Nano Lett. 10(4), 1271 (2010).Google Scholar
Mak, K.F., Lee, C., Hone, J., Shan, J., and Heinz, T.F.: Atomically think MoS2: A new direct-gap semiconductor. Phys. Rev. Lett. 105(13), 136805 (2010).Google Scholar
Boker, T., Severin, R., Muller, A., Janowitz, C., Manzke, R., Voss, D., Kruger, P., Mazur, A., and Pollmann, J.: Band structure of MoS2, MoSe2, and alpha-MoTe2: Angle-resolved photoelectron spectroscopy and ab initio calculations. Phys. Rev. B 64(23), 235305 (2001).Google Scholar
Klein, A., Tiefenbacher, S., Eyert, V., Pettenkofer, C., and Jaegermann, W.: Electronic band structure of single-crystal and single-layer WS2: Influence of interlayer van der Waals interactions. Phys. Rev. B 64(20), 205416 (2001).Google Scholar
Ramasubramaniam, A., Naveh, D., and Towe, E.: Tunable band gaps in bilayer transition-metal dichalcogenides. Phys. Rev. B 84(20), 205325 (2011).CrossRefGoogle Scholar
Lebegue, S. and Eriksson, O.: Electronic structure of two-dimensional crystals from ab initio theory. Phys. Rev. B 79(11), 115409 (2009).Google Scholar
Levendorf, M.P., Kim, C.J., Brown, L., Huang, P.Y., Havener, R.W., Muller, D.A., and Park, J.: Graphene and boron nitride lateral heterostructrures for atomically thin circuitry. Nature 488(7413), 627 (2012).CrossRefGoogle Scholar
Landman, U., Barnett, R.N., Scherbakov, A.G., and Avouris, P.: Metal-semiconductor nanocontacts: Silicon nanowires. Phys. Rev. Lett. 85(9), 1958 (2000).Google Scholar
Leonard, F. and Talin, A.A.: Size-dependent effects on electrical contacts to nanotubes and nanowires. Phys. Rev. Lett. 97(2), 026804 (2006).CrossRefGoogle ScholarPubMed
Nemec, N., Tomanek, D., and Cuniberti, G.: Contact dependence of carrier injection in carbon nanotubes: An ab initio study. Phys. Rev. Lett. 96(7), 076802 (2006).Google Scholar
Radisavljevic, B., Radenovic, A., Brivio, J., Giacometti, V., and Kis, A.: Single-layer MoS2 transistors. Nat. Nanotechnol. 6(3), 147 (2011).CrossRefGoogle ScholarPubMed
Popov, I., Seifert, G., and Tomanek, D.: Designing electrical contacts to MoS2 monolayers: A computational study. Phys. Rev. Lett. 108(15), 156802 (2012).CrossRefGoogle ScholarPubMed
Conley, H.J., Wang, B., Ziegler, J.I., Haglund, R.F., Pantelides, S.T., and Bolotin, K.I.: Bandgap engineering of strained monolayer and bilayer MoS2 . Nano Lett. 13(8), 3626 (2013).CrossRefGoogle ScholarPubMed
He, K., Poole, C., Mak, K.F., and Shan, J.: Experimental demonstration of continuous electronic structure tuning via strain in atomically thin MoS2 . Nano Lett. 13, 2931 (2013).Google Scholar
Lu, P., Wu, X., Guo, W., and Zeng, X.C.: Strain-dependent electronic and magnetic properties of MoS2 monolayer, bilayer, nanoribbons and nanotubes. Phys. Chem. Chem. Phys. 14, 13035 (2012).CrossRefGoogle ScholarPubMed
Scalise, E., Houssa, M., Pourtois, G., Afanasev, V., and Stesmans, A.: Strain-induced semiconductor to metal transition in the two dimensional honeycomb structure of MoS2 . Nano Res. 5, 43 (2012).CrossRefGoogle Scholar
Bertolazzi, S., Brivio, J., and Kis, A.: Stretching and breaking of ultrathin MoS2 . ACS Nano 5(12), 9703 (2011).Google Scholar
Sanchez-Perez, J.R., Boztug, C., Chen, F., Sudradjat, F.F., Paskiewicz, D.M., Jacobson, R.B., Lagally, M.G., and Paiella, R.: Direct-bandgap light-emitting germanium in tensilely strained nanomembranes. Proc. Natl. Acad. Sci. U.S.A. 108, 18893 (2011).CrossRefGoogle ScholarPubMed
Yun, W.S., Han, S.W., Hong, S.C., Kim, I.G., and Lee, J.D.: Thickness and strain effects on electronic structures of transition metal dichalcogenides: 2H-M X-2 semiconductors (M=Mo, W; X = S, Se, Te). Phys. Rev. B 85, 033305 (2012).Google Scholar
Feng, J., Qian, X., Huang, C., and Li, J.: Strain-engineered artificial atom as a broad-spectrum solar energy funnel. Nat. Photonics 6, 866–872 (2012).CrossRefGoogle Scholar
Yu, W.J., Liu, Y., Zhou, H., Yin, A., Li, Z., Huang, Y., and Duan, X.: Highly efficient gate-tunable photocurrent generation in vertical heterostructures of layered materials. Nat. Nanotechnol. 8, 952 (2013).Google Scholar
Britnell, L., Gorbachev, R.V., Jalil, R., Belle, B.D., Schedin, F., Mishchenko, A., Georgiou, T., Katsnelson, M.I., Eaves, L., Morozov, S.V., Peres, N.M.R., Leist, J., Geim, A.K., Novoselov, K.S., and Ponomarenko, L.A.: Field-effect tunneling transistor based on vertical graphene heterostructures. Science 335, 947 (2012).CrossRefGoogle ScholarPubMed
Georgiou, T., Jalil, R., Belle, B.D., Britnell, L., Gorbachev, R.V., Morozov, S.V., Kim, Y-J., Gholinia, A., Haigh, S.J., Makarovsky, O., Eaves, L., Ponomarenko, L.A., Geim, A.K., Novoselov, K.S., and Mishchenko, A.: Vertical field-effect transistor based on graphene-WS2 heterostructures for flexible and transparent electronics. Nat. Nanotechnol. 8(2), 100 (2013).Google Scholar
Britnell, L., Ribeiro, R.M., Eckmann, A., Jalil, R., Belle, B.D., Mishchenko, A., Kim, Y-J., Gorbachev, R.V., Georgiou, T., Morozov, S.V., Grigorenko, A.N., Geim, A.K., Casiraghi, C., Castro Neto, A.H., and Novoselov, K.S.: Strong light-matter interactions in heterostructures of atomically thin films. Science 340, 1311 (2013).CrossRefGoogle ScholarPubMed
Esmaeili-Rad, M.R. and Salahuddin, S.: High performance molybdenum disulfide amorphous silicon heterojunction photodetector. Sci. Rep. 3, 2345 (2013).Google Scholar
Podzorov, V., Gershenson, M.E., Kloc, C., Zeis, R., and Bucher, E.: High-mobility field-effect transistors based on transition metal dichalcogenides. Appl. Phys. Lett. 84(17), 3301 (2004).Google Scholar
Ghatak, S., Pal, A.N., and Ghosh, A.: Nature of electronic states in atomically thin MoS2 field-effect transistors. ACS Nano 5, 7707 (2011).Google Scholar
Fivaz, R. and Mooser, E.: Mobility of charge carriers in semiconducting layer structures. Phys. Rev. 163(3), 743 (1967).Google Scholar
Debdeep, J. and Aniruddha, K.: Enhancement of carrier mobility in semiconductor nanostructures by dielectric engineering. Phys. Rev. Lett. 98, 136805 (2007).Google Scholar
Chen, F., Xia, J., Ferry, D.K., and Tao, N.: Dielectric screening enhanced performance in graphene FET. Nano Lett. 9, 2571 (2009).Google Scholar
Liu, H., Neal, A.T., and Ye, P.D.: Channel length scaling of MoS2 MOSFETS. ACS Nano 6, 8563 (2012).Google Scholar
Kim, K., Choi, J.Y., Kim, T., Cho, S.H., and Chung, H.J.: A role for graphene in silicon-based semiconductor devices. Nature 479(7373), 338 (2011).Google Scholar
Kaasbjerg, K., Thygesen, K.S., and Jacobsen, K.W.: Phonon-limited mobility in n-type single-layer MoS2 from first principles. Phys. Rev. B 85, 115317 (2012).Google Scholar
Kim, S., Konar, A., Hwang, W-S., Lee, J.H., Lee, J., Yang, J., Jung, C., Kim, H., Yoo, J-B., Choi, J-Y., Jin, Y.W., Lee, S.Y., Jena, D., Choi, W., and Kim, K.: High-mobility and low-power thin-film transistors based on multilayer MoS2 crystals. Nat. Commun. 3, 1011 (2012).Google Scholar
Yoon, Y., Ganapathi, K., and Salahuddin, S.: How good can monolayer MoS2 transistors be?. Nano Lett. 11(9), 3768 (2011).CrossRefGoogle Scholar
Liu, L., Kumar, S.B., Ouyang, Y.J., and Guo, J.: Performance limits of monolayer transition metal dichalcogenide transistors. IEEE Trans. Electron Devices 58, 3042 (2011).Google Scholar
Bistritzer, R. and MacDonald, A.H.: Transport between twisted graphene layers. Phys. Rev. B 81, 245412 (2010).Google Scholar
Feenstra, R.M., Jena, D., and Gu, G.: Single-particle tunneling in doped graphene-insulator-graphene junctions. J. Appl. Phys. 111, 043711 (2012).Google Scholar
Perebeinos, V., Tersoff, J.D., and Avouris, P.: Phonon-mediated interlayer conductance in twisted graphene bilayers. Phys. Rev. Lett. 109, 236604 (2012).Google Scholar
Britnell, L., Gorbachev, R.V., Geim, A.K., Ponomarenko, L.A., Mishchenko, A., Greenaway, M.T., Fromhold, T.M., Novoselov, K.S., and Eaves, L.: Resonant tunnelling and negative differential conductance in graphene transistors. Nat. Commun. 4, 1794 (2013).Google Scholar
Radisavljevic, B., Whitwick, M.B., and Kis, A.: Integrated circuits and logic operations based on single-layer MoS2 . ACS Nano 5(12), 9934 (2011).Google Scholar
Wang, H., Yu, L., Lee, Y-H., Shi, Y., Hsu, A., Chin, M.L., Li, L-J., Dubey, M., Kong, J., and Palacios, T.: Integrated circuits based on bilayer MoS2 transistors. Nano Lett. 12(9), 4674 (2012).CrossRefGoogle ScholarPubMed
Tongay, S., Zhou, J., Ataca, C., Lo, K., Matthews, T.S., Li, J., Grossman, J.C., and Wu, J.: Thermally driven crossover from indirect toward direct bandgap in 2D semiconductors: MoSe2 versus MoS2 . Nano Lett. 12(11), 5576 (2012).Google Scholar
Yin, Z., Li, H., Li, H., Jiang, L., Shi, Y., Sun, Y., Lu, G., Zhang, Q., Chen, X., and Zhang, H.: Single-layer MoS2 phototransistors. ACS Nano 6(1), 74 (2012).Google Scholar
Lee, H.S., Min, S.W., Chang, Y.G., Park, M.K., Nam, T., Kim, H., Kim, J.H., Ryu, S., and Im, S.: MoS2 nanosheet phototransistors with thickness-modulated optical energy gap. Nano Lett. 12(7), 3695 (2012).Google Scholar
Gourmelon, E., Lignier, O., Hadouda, H., Couturier, G., Bernede, J.C., Tedd, J., Pouzet, J., and Salardenne, J.: MS2 (M=W, Mo) photosensitive thin films for solar cells. Sol. Energy Mater. Sol. Cells 46(2), 115 (1997).CrossRefGoogle Scholar
Polman, A. and Atwater, H.A.: Photonic design principles for ultrahigh-efficiency photovoltaics. Nat. Mater. 11(3), 174 (2012).Google Scholar
Bernardi, M., Palummo, M., and Grossman, J.C.: Extraordinary sunlight absorption and 1 nm-thick photovoltaics using two-dimensional monolayer materials. Nano Lett. 13(8), 3664 (2013).Google Scholar
Shanmugam, M., Bansal, T., Durcan, C.A., and Yu, B.: Molybdenum disulphide/titanium dioxide nanocomposite-poly 3-hexylthiophene bulk heterojunctions solar cell. Appl. Phys. Lett. 100, 153901 (2012).Google Scholar
Thomalla, M. and Tributsch, H.: Photosensitization of nanostructured TiO2 with WS2 quantum sheets. J. Phys. Chem. B 110, 12167 (2006).CrossRefGoogle ScholarPubMed
Coleman, J.N., Lotya, M., O’Neil, A., Bergin, S.D., King, P.J., Khan, U., Young, K., Gaucher, A., De, S., Smith, R.J., Shvets, I.V., Arora, S.K., Stanton, G., Kim, H.Y., Lee, K., Kim, G.T., Duesberg, G.S., Hallam, T., Boland, J.J., Wang, J.J., Donegan, J.F., Grunlan, J.C., Moriarty, G., Shmeliov, A., Nicholls, R.J., Perkins, J.M., Grieveson, E.M., Theuwissen, K., McComb, D.W., Nellist, P.D., and Nicolosi, V.: Two-dimensional nanosheets produced by liquid exfoliation of layered materials. Science 331(6017), 568 (2011).Google Scholar
Joensen, P., Frindt, R.F., and Morrison, S.R.: Single-layer MoS2 . Mater. Res. Bull. 21(4), 457 (1986).Google Scholar
Zhan, Y., Liu, Z., Najmaei, S., Ajayan, P.M., and Lou, J.: Large-area vapor phase growth and characterization of MoS2 atomic layers on a SiO2 substrate. Small 8(7), 966 (2012).Google Scholar
Yu, Y., Li, C., Liu, Y., Su, L., Zhang, Y., and Cao, L.: Controlled scalable synthesis of uniform, high-quality monolayer and few layer MoS2 films. Sci. Rep. 3, 1866 (2013).Google Scholar
Koma, A. and Yoshimura, K.: Ultra-sharp interfaces grown with van der Waals epitaxy. Surf. Sci. 174, 556 (1986).Google Scholar