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Distinct photoluminescence and Raman spectroscopy signatures for identifying highly crystalline WS2 monolayers produced by different growth methods

  • Amber McCreary (a1), Ayse Berkdemir (a2), Junjie Wang (a3), Minh An Nguyen (a4), Ana Laura Elías (a5), Néstor Perea-López (a5), Kazunori Fujisawa (a5), Bernd Kabius (a6), Victor Carozo (a7), David A. Cullen (a8), Thomas E. Mallouk (a9), J. Zhu (a10) and Mauricio Terrones (a11)...

Transition metal dichalcogenides such as WS2 show exciting promise in electronic and optoelectronic applications. Significant variations in the transport, Raman, and photoluminescence (PL) can be found in the literature, yet it is rarely addressed why this is. In this report, Raman and PL of monolayered WS2 produced via different methods are studied and distinct features that indicate the degree of crystallinity of the material are observed. While the intensity of the LA(M) Raman mode is found to be a useful indicator to assess the crystallinity, PL is drastically more sensitive to the quality of the material than Raman spectroscopy. We also show that even exfoliated crystals, which are usually regarded as the most pristine material, can contain large amounts of defects that would not be apparent without Raman and PL measurements. These findings can be applied to the understanding of other two-dimensional heterostructured systems.

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1. Geim, A.K. and Novoselov, K.S.: The rise of graphene. Nat. Mater. 6(3), 183 (2007).
2. Kim, K.K., Hsu, A., Jia, X., Kim, S.M., Shi, Y., Dresselhaus, M., Palacios, T., and Kong, J.: Synthesis and characterization of hexagonal boron nitride film as a dielectric layer for graphene devices. ACS Nano 6(10), 8583 (2012).
3. 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.: Boron nitride substrates for high-quality graphene electronics. Nat. Nanotechnol. 5(10), 722 (2010).
4. Novoselov, K.S. and Castro Neto, A.H.: Two-dimensional crystals-based heterostructures: Materials with tailored properties. Phys. Scr. T146, 014006 (2012).
5. 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(11), 699 (2012).
6. Berkdemir, A., Gutierrez, H.R., Botello-Mendez, A.R., Perea-Lopez, N., Elias, A.L., Chia, C-I., Wang, B., Crespi, V.H., Lopez-Urias, F., Charlier, J-C., Terrones, H., and Terrones, M.: Identification of individual and few layers of WS2 using Raman spectroscopy. Sci. Rep. 3, 1755 (2013).
7. 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(4), 263 (2013).
8. Mak, K.F., Lee, C., Hone, J., Shan, J., and Heinz, T.F.: Atomically thin MoS2: A new direct-gap semiconductor. Phys. Rev. Lett. 105(13), 136805 (2010).
9. Lopez-Sanchez, O., Lembke, D., Kayci, M., Radenovic, A., and Kis, A.: Ultrasensitive photodetectors based on monolayer MoS2 . Nat. Nanotechnol. 8(7), 497 (2013).
10. Butler, S.Z., Hollen, S.M., Cao, L., Cui, Y., Gupta, J.A., Gutierrez, H.R., Heinz, T.F., Hong, S.S., Huang, J., Ismach, A.F., Johnston-Halperin, E., Kuno, M., Plashnitsa, V.V., Robinson, R.D., Ruoff, R.S., Salahuddin, S., Shan, J., Shi, L., Spencer, M.G., Terrones, M., Windl, W., and Goldberger, J.E.: Progress, challenges, and opportunities in two-dimensional materials beyond graphene. ACS Nano 7(4), 2898 (2013).
11. Jariwala, D., Sangwan, V.K., Lauhon, L.J., Marks, T.J., and Hersam, M.C.: Emerging device applications for semiconducting two-dimensional transition metal dichalcogenides. ACS Nano 8(2), 1102 (2014).
12. Ganatra, R. and Zhang, Q.: Few-layer MoS2: A promising layered semiconductor. ACS Nano 8(5), 4074 (2014).
13. Gutierrez, H.R., Perea-Lopez, N., Elias, A.L., Berkdemir, A., Wang, B., Lv, R., Lopez-Urias, F., Crespi, V.H., Terrones, H., and Terrones, M.: Extraordinary room-temperature photoluminescence in triangular WS2 monolayers. Nano Lett. 13(8), 3447 (2013).
14. Elias, A.L., Perea-Lopez, N., Castro-Beltran, A., Berkdemir, A., Lv, R.T., Feng, S.M., Long, A.D., Hayashi, T., Kim, Y.A., Endo, M., Gutierrez, H.R., Pradhan, N.R., Balicas, L., Houk, T.E.M., Lopez-Urias, F., Terrones, H., and Terrones, M.: Controlled synthesis and transfer of large-area WS2 sheets: From single layer to few layers. ACS Nano 7(6), 5235 (2013).
15. Orofeo, C.M., Suzuki, S., Sekine, Y., and Hibino, H.: Scalable synthesis of layer-controlled WS2 and MoS2 sheets by sulfurization of thin metal films. Appl. Phys. Lett. 105(8), 83112 (2014).
16. Jo, S., Ubrig, N., Berger, H., Kuzmenko, A.B., and Morpurgo, A.F.: Mono- and bilayer WS2 light-emitting transistors. Nano Lett. 14(4), 2019 (2014).
17. Zhang, Y., Zhang, Y., Ji, Q., Ju, J., Yuan, H., Shi, J., Gao, T., Ma, D., Liu, M., Chen, Y., Song, X., Hwang, H.Y., Cui, Y., and Liu, Z.: Controlled growth of high-quality monolayer WS2 layers on sapphire and imaging its grain boundary. ACS Nano 7(10), 8963 (2013).
18. Rong, Y., Fan, Y., Leen Koh, A., Robertson, A.W., He, K., Wang, S., Tan, H., Sinclair, R., and Warner, J.H.: Controlling sulphur precursor addition for large single crystal domains of WS2 . Nanoscale 6(20), 12096 (2014).
19. 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).
20. Mitioglu, A.A., Plochocka, P., Jadczak, J.N., Escoffier, W., Rikken, G.L.J.A., Kulyuk, L., and Maude, D.K.: Optical manipulation of the exciton charge state in single-layer tungsten disulfide. Phys. Rev. B 88(24), 245403 (2013).
21. Zeng, H.L., Liu, G.B., Dai, J.F., Yan, Y.J., Zhu, B.R., He, R.C., Xie, L., Xu, S.J., Chen, X.H., Yao, W., and Cui, X.D.: Optical signature of symmetry variations and spin-valley coupling in atomically thin tungsten dichalcogenides. Sci. Rep. 3, 1608 (2013).
22. Novoselov, K.S., 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).
23. Eda, G., Yamaguchi, H., Voiry, D., Fujita, T., Chen, M.W., and Chhowalla, M.: Photoluminescence from chemically exfoliated MoS2 . Nano Lett. 11(12), 5111 (2011).
24. Coleman, J.N., Lotya, M., O'Neill, 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).
25. Matte, H.S.S.R., Gomathi, A., Manna, A.K., Late, D.J., Datta, R., Pati, S.K., and Rao, C.N.R.: MoS2 and WS2 analogues of graphene. Angew. Chem., Int. Ed. 49(24), 4059 (2010).
26. Frindt, R.F.: Single crystals of MoS2 several molecular layers thick. J. Appl. Phys. 37(4), 1928 (1966).
27. Joensen, P., Frindt, R.F., and Morrison, S.R.: Single layer MoS2 . Mater. Res. Bull. 21(4), 457 (1986).
28. Golasa, K., Grzeszczyk, M., Korona, K.P., Bozek, R., Binder, J., Szczytko, J., Wysmolek, A., and Babinski, A.: Optical properties of molybdenum disulfide (MoS2). Acta Phys. Pol., A 124(5), 849 (2013).
29. Schäfer, H., Grofe, T., and Trenkel, M.: The chemical transport of molybdenum and tungsten and of their dioxides and sulfides. J. Solid State Chem. 8(1), 14 (1973).
30. Lieth, R.M.A.: Preparation and Crystal Growth of Materials with Layered Structures, Vol. 1 (D. Reidel Pub. Co, Dordrecht, 1977).
31. Nicolosi, V., Chhowalla, M., Kanatzidis, M.G., Strano, M.S., and Coleman, J.N.: Liquid exfoliation of layered materials. Science 340(6139), 1420 (2013).
32. Dresselhaus, M.S. and Dresselhaus, G.: Intercalation compounds of graphite. Adv. Phys. 30(2), 139 (1981).
33. van der Zande, A.M., Huang, P.Y., Chenet, D.A., Berkelbach, T.C., You, Y.M., Lee, G.H., Heinz, T.F., Reichman, D.R., Muller, D.A., and Hone, J.C.: Grains and grain boundaries in highly crystalline monolayer molybdenum disulphide. Nat. Mater. 12(6), 554 (2013).
34. Shaw, J.C., Zhou, H., Chen, Y., Weiss, N.O., Liu, Y., Huang, Y., and Duan, X.: Chemical vapor deposition growth of monolayer MoSe2 nanosheets. Nano Res. 7(4), 511 (2014).
35. Kang, K., Xie, S., Huang, L., Han, Y., Huang, P.Y., Mak, K.F., Kim, C-J., Muller, D., and Park, J.: High-mobility three-atom-thick semiconducting films with wafer-scale homogeneity. Nature 520(7549), 656 (2015).
36. 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).
37. Baugher, B.W.H., Churchill, H.O.H., Yang, Y., and Jarillo-Herrero, P.: Intrinsic electronic transport properties of high-quality monolayer and bilayer MoS2 . Nano Lett. 13(9), 4212 (2013).
38. Fang, H., Chuang, S., Chang, T.C., Takei, K., Takahashi, T., and Javey, A.: High-performance single layered WSe2 p-FETs with chemically doped contacts. Nano Lett. 12(7), 3788 (2012).
39. Amani, M., Chin, M.L., Birdwell, A.G., O'Regan, T.P., Najmaei, S., Liu, Z., Ajayan, P.M., Lou, J., and Dubey, M.: Electrical performance of monolayer MoS2 field-effect transistors prepared by chemical vapor deposition. Appl. Phys. Lett. 102(19), 193107 (2013).
40. Perea-Lopez, N., Elias, A.L., Berkdemir, A., Castro-Beltran, A., Gutierrez, H.R., Feng, S., Lv, R., Hayashi, T., Lopez-Urias, F., Ghosh, S., Muchharla, B., Talapatra, S., Terrones, H., and Terrones, M.: Photosensor device based on few-layered WS2 films. Adv. Funct. Mater. 23(44), 5511 (2013).
41. Perea-López, N., Lin, Z., Pradhan, N., Iñiguez-Rábago, A., Elías, A.L., McCreary, A., Lou, J., Ajayan, P.M., Terrones, H., Balicas, L., and Terrones, M.: CVD-grown monolayered MoS2 as an effective photosensor operating at low-voltage. 2D Mater. 1(1), 011004 (2014).
42. Wu, C-C., Jariwala, D., Sangwan, V.K., Marks, T.J., Hersam, M.C., and Lauhon, L.J.: Elucidating the photoresponse of ultrathin MoS2 field-effect transistors by scanning photocurrent microscopy. J. Phys. Chem. Lett. 4(15), 2508 (2013).
43. Baugher, B.W.H., Churchill, H.O.H., Yang, Y., and Jarillo-Herrero, P.: Optoelectronic devices based on electrically tunable p-n diodes in a monolayer dichalcogenide. Nat. Nanotechnol. 9(4), 262 (2014).
44. 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(6138), 1311 (2013).
45. 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).
46. Zhang, Z., Zou, X., Crespi, V.H., and Yakobson, B.I.: Intrinsic magnetism of grain boundaries in two-dimensional metal dichalcogenides. ACS Nano 7(12), 10475 (2013).
47. Mak, K.F., He, K.L., Shan, J., and Heinz, T.F.: Control of valley polarization in monolayer MoS2 by optical helicity. Nat. Nanotechnol. 7(8), 494 (2012).
48. Mak, K.F., McGill, K.L., Park, J., and McEuen, P.L.: The valley Hall effect in MoS2 transistors. Science 344(6191), 1489 (2014).
49. Hao, Y., Bharathi, M.S., Wang, L., Liu, Y., Chen, H., Nie, S., Wang, X., Chou, H., Tan, C., Fallahazad, B., Ramanarayan, H., Magnuson, C.W., Tutuc, E., Yakobson, B.I., McCarty, K.F., Zhang, Y-W., Kim, P., Hone, J., Colombo, L., and Ruoff, R.S.: The role of surface oxygen in the growth of large single-crystal graphene on copper. Science 342(6159), 720 (2013).
50. Vlassiouk, I., Regmi, M., Fulvio, P.F., Dai, S., Datskos, P., Eres, G., and Smirnov, S.: Role of hydrogen in chemical vapor deposition growth of large single-crystal graphene. ACS Nano 5(7), 6069 (2011).
51. Wood, J.D., Schmucker, S.W., Lyons, A.S., Pop, E., and Lyding, J.W.: Effects of polycrystalline Cu substrate on graphene growth by chemical vapor deposition. Nano Lett. 11(11), 4547 (2011).
52. Li, X., Cai, W., Colombo, L., and Ruoff, R.S.: Evolution of graphene growth on Ni and Cu by carbon isotope labeling. Nano Lett. 9(12), 4268 (2009).
53. Shin, W.C., Yoon, T., Mun, J.H., Kim, T.Y., Choi, S-Y., Kim, T-S., and Cho, B.J.: Doping suppression and mobility enhancement of graphene transistors fabricated using an adhesion promoting dry transfer process. Appl. Phys. Lett. 103(24), 243504 (2013).
54. Casiraghi, C., Pisana, S., Novoselov, K.S., Geim, A.K., and Ferrari, A.C.: Raman fingerprint of charged impurities in graphene. Appl. Phys. Lett. 91(23), 233108 (2007).
55. Casiraghi, C.: Probing disorder and charged impurities in graphene by Raman spectroscopy. Phys. Status Solidi RRL 3(6), 175 (2009).
56. Ji, Q., Zhang, Y., Gao, T., Zhang, Y., Ma, D., Liu, M., Chen, Y., Qiao, X., Tan, P-H., Kan, M., Feng, J., Sun, Q., and Liu, Z.: Epitaxial monolayer MoS2 on mica with novel photoluminescence. Nano Lett. 13(8), 3870 (2013).
57. Amani, M., Chin, M.L., Mazzoni, A.M., Burke, R.A., Najmaei, S., Ajayan, P.M., Lou, J., and Dubey, M.: Growth-substrate induced performance degradation in chemically synthesized monolayer MoS2 field effect transistors. Appl. Phys. Lett. 104(20), 203506 (2014).
58. Zhou, W., Zou, X.L., Najmaei, S., Liu, Z., Shi, Y.M., Kong, J., Lou, J., Ajayan, P.M., Yakobson, B.I., and Idrobo, J.C.: Intrinsic structural defects in monolayer molybdenum disulfide. Nano Lett. 13(6), 2615 (2013).
59. Azizi, A., Zou, X., Ercuis, P., Zhang, Z., Elias, A.L., Perea-Lopez, N., Terrones, M., Yakobson, B.I., and Alem, N.: Atomic-scale observation of grains and grain boundary in monolayers of WS2 . Microsc. Microanal. 20(S3), 1084 (2014).
60. Ferrari, A.C., Meyer, J.C., Scardaci, V., Casiraghi, C., Lazzeri, M., Mauri, F., Piscanec, S., Jiang, D., Novoselov, K.S., Roth, S., and Geim, A.K.: Raman spectrum of graphene and graphene layers. Phys. Rev. Lett. 97(18), 187401 (2006).
61. Li, H., Zhang, Q., Yap, C.C.R., Tay, B.K., Edwin, T.H.T., Olivier, A., and Baillargeat, D.: From bulk to monolayer MoS2: Evolution of raman scattering. Adv. Funct. Mat. 22(7), 1385 (2012).
62. Lee, C., Yan, H., Brus, L.E., Heinz, T.F., Hone, J., and Ryu, S.: Anomalous lattice vibrations of single- and few-layer MoS2 . ACS Nano 4(5), 2695 (2010).
63. Ni, Z.H., Yu, T., Lu, Y.H., Wang, Y.Y., Feng, Y.P., and Shen, Z.X.: Uniaxial strain on graphene: Raman spectroscopy study and band-gap opening. ACS Nano 2(11), 2301 (2008).
64. Mohiuddin, T.M.G., Lombardo, A., Nair, R.R., Bonetti, A., Savini, G., Jalil, R., Bonini, N., Basko, D.M., Galiotis, C., Marzari, N., Novoselov, K.S., Geim, A.K., and Ferrari, A.C.: Uniaxial strain in graphene by raman spectroscopy: G peak splitting, Gruneisen parameters, and sample orientation. Phys. Rev. B 79(20), 205433 (2009).
65. Rice, C., Young, R.J., Zan, R., Bangert, U., Wolverson, D., Georgiou, T., Jalil, R., and Novoselov, K.S.: Raman-scattering measurements and first-principles calculations of strain-induced phonon shifts in monolayer MoS2 . Phys. Rev. B 87(8), 081307(R) (2013).
66. Conley, H.J., Wang, B., Ziegler, J.I., Haglund, R.F. Jr., Pantelides, S.T., and Bolotin, K.I.: Bandgap engineering of strained monolayer and bilayer MoS2 . Nano Lett. 13(8), 3626 (2013).
67. Desai, S.B., Seol, G., Kang, J.S., Fang, H., Battaglia, C., Kapadia, R., Ager, J.W., Guo, J., and Javey, A.: Strain-induced indirect to direct bandgap transition in multi layer WSe2 . Nano Lett. 14(8), 4592 (2014).
68. Ferrari, A.C.: Raman spectroscopy of graphene and graphite: Disorder, electron-phonon coupling, doping and nonadiabatic effects. Solid State Commun. 143(1–2), 47 (2007).
69. Das, A., Pisana, S., Chakraborty, B., Piscanec, S., Saha, S.K., Waghmare, U.V., Novoselov, K.S., Krishnamurthy, H.R., Geim, A.K., Ferrari, A.C., and Sood, A.K.: Monitoring dopants by Raman scattering in an electrochemically top-gated graphene transistor. Nat. Nanotechnol. 3(4), 210 (2008).
70. Mak, K.F., He, K.L., Lee, C., Lee, G.H., Hone, J., Heinz, T.F., and Shan, J.: Tightly bound trions in monolayer MoS2 . Nat. Mater. 12(3), 207 (2013).
71. Terrones, H., Del Corro, E., Feng, S., Poumirol, J.M., Rhodes, D.R., Smirnov, D., Pradhan, N.R., Lin, Z., Nguyen, M.A.T., Elias, A.L., Mallouk, T.E.M., Balicas, L., Pimenta, M.A., and Terrones, M.: New first order Raman-active modes in few layered transition metal dichalcogenides. Sci. Rep. 4, 4215 (2014).
72. Mignuzzi, S., Pollard, A.J., Bonini, N., Brennan, B., Gilmore, I.S., Pimenta, M.A., Richards, D., and Roy, D.: Effects of disorder on Raman scattering of single-layer MoS2 . Phys. Rev. B 91(19), 195411 (2015).
73. Pisoni, A., Jacimovic, J., Barisic, O.S., Walter, A., Nafradi, B., Bugnon, P., Magrez, A., Berger, H., Revay, Z., and Forro, L.: The role of transport agents in MoS2 single crystals. J. Phys. Chem. C 119(8), 3918 (2015).
74. Legma, J.B., Vacquier, G., and Casalot, A.: Chemical-vapor transport of molybdenum and tungsten diselenides by various transport agents. J. Crystal Growth 130(1–2), 253 (1993).
75. Peimyoo, N., Shang, J., Cong, C., Shen, X., Wu, X., Yeow, E.K.L., and Yu, T.: Nonblinking, intense two-dimensional light emitter: Mono layer WS2 triangles. ACS Nano 7(12), 10985 (2013).
76. Mouri, S., Miyauchi, Y., and Matsuda, K.: Tunable photoluminescence of monolayer MoS2 via chemical doping. Nano Lett. 13(12), 5944 (2013).
77. Sercombe, D., Schwarz, S., Del Pozo-Zamudio, O., Liu, F., Robinson, B.J., Chekhovich, E.A., Tartakovskii, I.I., Kolosov, O., and Tartakovskii, A.I.: Optical investigation of the natural electron doping in thin MoS2 films deposited on dielectric substrates. Sci. Rep. 3, 3489 (2013).
78. Najmaei, S., Liu, Z., Zhou, W., Zou, X.L., Shi, G., Lei, S.D., Yakobson, B.I., Idrobo, J.C., Ajayan, P.M., and Lou, J.: Vapour phase growth and grain boundary structure of molybdenum disulphide atomic layers. Nat. Mater. 12(8), 754 (2013).
79. Jones, A.M., Yu, H., Ross, J.S., Klement, P., Ghimire, N.J., Yan, J., Mandrus, D.G., Yao, W., and Xu, X.: Spin-layer locking effects in optical orientation of exciton spin in bilayer WSe2 . Nat. Phys. 10(2), 130 (2014).
80. Ross, J.S., Wu, S.F., Yu, H.Y., Ghimire, N.J., Jones, A.M., Aivazian, G., Yan, J.Q., Mandrus, D.G., Xiao, D., Yao, W., and Xu, X.D.: Electrical control of neutral and charged excitons in a monolayer semiconductor. Nat. Commun. 4, 1474 (2013).
81. Lin, J.D., Han, C., Wang, F., Wang, R., Xiang, D., Qin, S., Zhang, X-A., Wang, L., Zhang, H., Wee, A.T.S., and Chen, W.: Electron-Doping-enhanced trion formation in mono layer molybdenum disulfide functionalized with cesium carbonate. ACS Nano 8(5), 5323 (2014).
82. Tongay, S., Suh, J., Ataca, C., Fan, W., Luce, A., Kang, J.S., Liu, J., Ko, C., Raghunathanan, R., Zhou, J., Ogletree, F., Li, J., Grossman, J.C., and Wu, J.: Defects activated photoluminescence in two-dimensional semiconductors: Interplay between bound, charged, and free excitons. Sci. Rep. 3, 2657 (2013).
83. Chow, P.K., Jacobs-Gedrim, R.B., Gao, J., Lu, T-M., Yu, B., Terrones, H., and Koratkar, N.: Defect-induced photoluminescence in mono layer semiconducting transition metal dichalcogenides. ACS Nano 9(2), 1520 (2015).
84. Bhimanapati, G.R., Lin, Z., Meunier, V., Jung, Y., Cha, J., Das, S., Xiao, D., Son, Y., Strano, M.S., Cooper, V.R., Liang, L., Louie, S.G., Ringe, E., Zhou, W., Kim, S.S., Naik, R.R., Sumpter, B.G., Terrones, H., Xia, F., Wang, Y., Zhu, J., Akinwande, D., Alem, N., Schuller, J.A., Schaak, R.E., Terrones, M., and Robinson, J.: Recent advances in two-dimensional materials beyond graphene. ACS Nano 9(12), 11509 (2015).
85. Gong, Y., Liu, Z., Lupini, A.R., Shi, G., Lin, J., Najmaei, S., Lin, Z., Elias, A.L., Berkdemir, A., You, G., Terrones, H., Terrones, M., Vajtai, R., Pantelides, S.T., Pennycook, S.J., Lou, J., Zhou, W., and Ajayan, P.M.: Band gap engineering and layer-by-layer mapping of selenium-doped molybdenum disulfide. Nano Lett. 14(2), 442 (2014).
86. Gong, Y., Lin, J., Wang, X., Shi, G., Lei, S., Lin, Z., Zou, X., Ye, G., Vajtai, R., Yakobson, B.I., Terrones, H., Terrones, M., Tay, B.K., Lou, J., Pantelides, S.T., Liu, Z., Zhou, W., and Ajayan, P.M.: Vertical and in-plane heterostructures from WS2/MoS2 monolayers. Nat. Mater. 13(12), 1135 (2014).
87. Das, S., Robinson, J.A., Dubey, M., Terrones, H., and Terrones, M.: Beyond graphene: Progress in novel two-dimensional materials and van der waals solids. Annu. Rev. Mater. Res. 45, 1 (2015).
88. Lv, R., Robinson, J.A., Schaak, R.E., Sun, D., Sun, Y.F., Mallouk, T.E., and Terrones, M.: Transition metal dichalcogenides and beyond: Synthesis, properties, and applications of single- and few-layer nanosheets. Acc. Chem. Res. 48(1), 56 (2015).
89. Terrones, H., Lopez-Urias, F., and Terrones, M.: Novel hetero-layered materials with tunable direct band gaps by sandwiching different metal disulfides and diselenides. Sci. Rep. 3, 1549 (2013).
90. Ceballos, F., Bellus, M.Z., Chiu, H-Y., and Zhao, H.: Ultrafast charge separation and indirect exciton formation in a MoS2-MoSe2 van der Waals heterostructure. ACS Nano 8(12), 12717 (2014).
91. Bellus, M.Z., Ceballos, F., Chiu, H-Y., and Zhao, H.: Tightly bound trions in transition metal dichalcogenide heterostructures. ACS Nano 9(6), 6459 (2015).
92. Geim, A.K. and Grigorieval, I.V.: van der Waals heterostructures. Nature 499(7459), 419 (2013).
93. Lui, C.H., Ye, Z., Ji, C., Chiu, K-C., Chou, C-T., Andersen, T.I., Means-Shively, C., Anderson, H., Wu, J-M., Kidd, T., Lee, Y-H., and He, R.: Observation of interlayer phonon modes in van der Waals heterostructures. Phys. Rev. B 91(16), 165403 (2015).
94. Huo, N., Wei, Z., Meng, X., Kang, J., Wu, F., Li, S-S., Wei, S-H., and Li, J.: Interlayer coupling and optoelectronic properties of ultrathin two-dimensional heterostructures based on graphene, MoS2 and WS2 . J. Mater. Chem. C 3(21), 5467 (2015).
95. Huo, N., Tongay, S., Guo, W., Li, R., Fan, C., Lu, F., Yang, J., Li, B., Li, Y., and Wei, Z.: Novel optical and electrical transport properties in atomically thin WSe2/MoS2 p-n heterostructures. Adv. Electron. Mater. 1(5), 1400066 (2015).
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Journal of Materials Research
  • ISSN: 0884-2914
  • EISSN: 2044-5326
  • URL: /core/journals/journal-of-materials-research
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