單層過度金屬硫族化合物因其多元的電子結構與光學特性在次世代的電子元件應用以及基礎科學研究中具有無窮的潛力。隨著凡德瓦異質結構概念的提出，不同特性的二維材料能夠輕易地互相結合並產生更多元的材料特性以用於拓展材料的應用範疇。本論文藉由掃描探針顯微術研究化學氣相沉積法所合成之二維材料以及其異質結構的表面特徵與電子結構。
基於良好的材料轉移技術，透過去離子水作為材料轉移的媒介將合成後的單層二維材料轉移至特定基板上，且得到乾淨以及良好介面的試片以用於超高真空的掃描探針顯微鏡中進行研究。我們成功的搭起材料生長與超高真空分析系統的連結以用於更多基礎科學的研究。
再者，不同的材料堆疊結構也成功地透過掃描探針顯微術成功的被解析出來，這些不同的材料堆疊結構透過不同的電子結構耦合情形能夠創造出各式各樣的物理特性，像是超導現象、電子自旋谷耦合能態、層間量子化激子等物理現象都與材料堆疊的耦合情形具有高度關聯性。掃描電子顯微術具有同時解析材料表面結構以及其對應電子結構的能力，像是應變、點缺陷、以及異質介面能帶偏移的特性。藉由理論的推導，不同的材料堆疊結構所對應的堆疊情形能夠清楚地被解析出來。材料堆疊所形成的耦合的電子結構也能藉由掃圖過程中參數的調控形成不同的影像對比可用來了解材料間的電子結構交互作用情形。
最後，藉由探測側向二維異質結構的材料介面，我們成功的解析了其晶體結構以及電子結構，也首度證實了二硫化鉬二硫化鎢側向異質接面為無應變的理想材料介面以及第二型的能帶偏移特徵。

Monolayer two-dimensional (2D) transition metal dichalcogenides (TMDs) have demonstrate great potential for future applications and fundamental physics studies because of wide variety of its electronic and optical properties. With the emergence of van der Waals (vdW) heterostructures, the applications of 2D materials has been extended by the combination of different kinds monolayers without the consideration of lattice mismatch or process feasibility. This dissertation focuses on the electronic properties of the transferred as-grown monolayer TMDs and its heterostructures by scanning tunneling microscopy and spectroscopy (STM/STS).
We begin with the study of clean transferring techniques of the as-grown monolayer synthesized by chemical vapor deposition (CVD) process. We find that the water is an ideal media for clean transferring process of CVD-grown sample. With this technique, the as-grown 2D lattices are successfully integrated into the ultra-high vacuum system for STM/STS study.
Then, multiple Moiré of different kinds of stacking configurations are observed and characterized by STM imaging. The modulated periodic potential of Moiré patterns is due to the twisting between stacked layers which offers an extra degree of freedom to tailor materials property. Such as unconventional superconductivity, coupled spin-valley states and quantized interlayer excitons are highly related to the electronic couplings between stacked monolayers. The STM/STS has the ability to provide the direct evidence of the Moiré superlattice and correlate coupled parameters among local electronic structures, strains, defects and band alignment at atomic scale. Diverse stacking configurations of the TMDs heterostructures are demonstrated with our theoretical predictions. The tunable coupled electronic structures of stacked monolayers are also presented to demonstrate the electronic structure difference under different imaging conditions.
Finally, we probe the geometric and electronic structures at the vicinity of lateral stitched MoS2-WS2 heterostructures. By the identification of its lattice structures and spatially resolved electronic structures at both sides of the boundary, a strain free signature of lateral stitched boundary is evidenced. Drawing from all the research presented, we arrive at a favorable conclusion about the viability of STM/STS study on transferred 2D lattices.

Contents

Abstract I
摘要 III
Acknowledgement IV
1 Introduction 1
1.1 Introduction to TMDs 1
1.2 Vertically Stacked van der Waal Heterostructures 5
1.3 Electronic Structures of TMDs 11

2 Experimental Methods and Techniques 16
2.1 Preparation of Monolayer TMDs via CVD Synthesis 16
2.1.1 Growth of Individual MoS2 and WS2¬ 17
2.1.2 Growth of MoS2-WS2 Lateral Heterostructure 17
2.2 Ultra-clean transfer of CVD-grown TMDs for STM study 19
2.2.1 Water-mediated Transferring Process 19
2.2.2 PDMS-assisted Water-mediated Transferring Process 20
2.3 Characterization of the transferred TMDs monolayer 22
2.4 Scanning Tunneling Microscopy and Spectroscopy 25
2.4.1 STM Imaging 26
2.4.2 Scanning Tunneling Spectroscopy 27
2.4.3 Electrochemical Etching Process for Tip Preparation. 28
2.4.4 Experimental Data Processing 29

3 Scanning Tunneling Microscopy and Spectroscopy of TMDs 30
3.1 Surface Topography of Transferred Monolayers 30
3.2 Atomic and Electronic Structures of Monolayer TMDs 38
3.3 Surface Features Characterized by STM/STS 41
3.3.1 The Correlation of Point Defect and Step Edge of MoS2 41
3.3.2 Boundary of the 2D lattices 50
3.4 Conclusions 52

4 STM Imaging of TMDs Vertical Heterostructures 54
4.1 STM Imaging of Hetero-Interface Moiré Superstructures 54
4.2 STM Imaging of Homo-Interface Moiré Superstructures 58
4.3 Identification of Moiré with Theoretical Predictions 61
4.4 Coherent Stacking and Twist Stacking of Homo-interface 70
4.5 Moiré – atomic Contrast transition with Bias Tuning 71
4.5.1 Experimental Observations 71
4.5.2 Intensity Ratio 73
4.5.3 Electrons Tunneling Model 75
4.6 Conclusions 79

5 STM/S of MoS2-WS2 Lateral Heterostructures 81
5.1 Samples 82
5.2 STM Results 83
5.3 Lattice Coherency Across the Boundary 85
5.4 Spatially Resolved Electronic Structure Across the Boundary 88
5.5 Conclusions 89

6 Conclusions & Future Prospect 91
6.1 Conclusions 91
6.2 Future Prospect 92

References 95

Reference

[1] K.S. Novoselov, A.K. Geim, S.V. Morozov, D. Jiang, Y. Zhang, S.V. Dubonos, I.V. Grigorieva, A.A. Firsov. “Electric Field Effect in Atomically Thin Carbon Films“. Science, 2004, 306, 666-669.

[2] C. Gong, H. Zhang, W. Wang, L. Colombo, R.M. Wallace, K. Cho. “Band alignment of two-dimensional transition metal dichalcogenides: Application in tunnel field effect transistors“. Appl. Phys. Lett., 2013, 103, 053513.

[3] M. Chhowalla, H.S. Shin, G. Eda, L.-J. Li, K.P. Loh, H. Zhang. “The chemistry of two-dimensional layered transition metal dichalcogenide nanosheets“. Nat. Chem., 2013, 5, 263-275.

[4] A.K. Geim, I.V. Grigorieva. “Van der Waals heterostructures“. Nature, 2013, 499, 419-425.

[5] K.S. Novoselov, D. Jiang, F. Schedin, T.J. Booth, V.V. Khotkevich, S.V. Morozov, A.K. Geim. “Two-dimensional atomic crystals“. Proc. Natl. Acad. Sci. U.S.A., 2005, 102, 10451-10453.

[6] A. Splendiani, L. Sun, Y. Zhang, T. Li, J. Kim, C.-Y. Chim, G. Galli, F. Wang. “Emerging Photoluminescence in Monolayer MoS2“. Nano Lett., 2010, 10, 1271-1275.

[7] K.F. Mak, C. Lee, J. Hone, J. Shan, T.F. Heinz. “Atomically Thin MoS2: A New Direct-Gap Semiconductor“. Phys. Rev. Lett., 2010, 105, 136805.

[8] Q.H. Wang, K. Kalantar-Zadeh, A. Kis, J.N. Coleman, M.S. Strano. “Electronics and optoelectronics of two-dimensional transition metal dichalcogenides“. Nat. Nanotechnol., 2012, 7, 699–712.

[9] D. Lembke, S. Bertolazzi, A. Kis. “Single-Layer MoS2 Electronics“. Acc. Chem. Res., 2015, 48, 1, 100-110

[10] Y. Cao, V. Fatemi, A. Demir, S. Fang, S.L. Tomarken, J.Y. Luo, J.D. Sanchez-Yamagishi, K. Watanabe, T. Taniguchi, E. Kaxiras, R.C. Ashoori, P. Jarillo-Herrero. “Correlated insulator behaviour at half-filling in magic-angle graphene superlattices“. Nature, 2018, 556, 80-84.

[11] Y. Cao, V. Fatemi, S. Fang, K. Watanabe, T. Taniguchi, E. Kaxiras, P. Jarillo-Herrero. “Unconventional superconductivity in magic-angle graphene superlattices“. Nature, 2018, 556, 43-50.

[12] S. Carr, S. Fang, P. Jarillo-Herrero, E. Kaxiras. “Pressure dependence of the magic twist angle in graphene superlattices“. Phys. Rev. B, 2018, 98, 085144.

[13] M. Yankowitz, S. Chen, H. Polshyn, Y. Zhang, K. Watanabe, T. Taniguchi, D. Graf, A.F. Young, C.R. Dean. “Tuning superconductivity in twisted bilayer graphene“. Science, 2019, 363, 1059-1064.

[14] M. Yankowitz, J. Xue, D. Cormode, J.D. Sanchez-Yamagishi, K. Watanabe, T. Taniguchi, P. Jarillo-Herrero, P. Jacquod, B.J. LeRoy. “Emergence of superlattice Dirac points in graphene on hexagonal boron nitride“. Nat. Phys., 2012, 8, 382-386.

[15] C.R. Dean, L. Wang, P. Maher, C. Forsythe, F. Ghahari, Y. Gao, J. Katoch, M. Ishigami, P. Moon, M. Koshino, T. Taniguchi, K. Watanabe, K.L. Shepard, J. Hone, P. Kim. “Hofstadter’s butterfly and the fractal quantum Hall effect in moiré superlattices.“ Nature, 2013, 497, 598-602.

[16] H. Terrones, F. López-Urías, M. Terrones. “Novel hetero-layered materials with tunable direct band gaps by sandwiching different metal disulfides and diselenides“. Sci. Rep., 2013, 3, 1549.

[17] K. Tran, G. Moody, F. Wu, X. Lu, J. Choi, K. Kim, A. Rai, D.A. Sanchez, J. Quan, A. Singh, J. Embley, A. Zepeda, M. Campbell, T. Autry, T. Taniguchi, K. Watanabe, N. Lu, S.K. Banerjee, K.L. Silverman, S. Kim, E. Tutuc, L. Yang, A.H. MacDonald, X. Li. “Evidence for moiré excitons in van der Waals heterostructures“. Nature, 2019, 567, 71-75.

[18] K.L. Seyler, P. Rivera, H. Yu, N.P. Wilson, E.L. Ray, D.G. Mandrus, J. Yan, W. Yao, X. Xu. “Signatures of moiré-trapped valley excitons in MoSe2/Wse2 heterobilayers“. Nature, 2019, 567, 66-70.

[19] Z. Zhang, P. Chen, X. Duan, K. Zang, J. Luo, X. Duan. “Robust epitaxial growth of two-dimensional heterostructures, multiheterostructures, and superlattices“. Science, 2017, 357, 788-792.

[20] C. Zhang, C.-P. Chuu, X. Ren, M.-Y. Li, L.-J. Li, C. Jin, M.-Y. Chou, C.-K. Shih. “Interlayer couplings, Moiré patterns, and 2D electronic superlattices in MoS2/WSe2 hetero-bilayers“. Sci. Adv., 2017, 3: e1601459

[21] Y. Gong, J. Lin, X. Wang, G. Shi, S. Lei, Z. Lin, X. Zou, G. Ye, R. Vajtai, B.I. Yakobson, H. Terrones, M. Terrones, Beng K. Tay, J. Lou, S.T. Pantelides, Z. Liu, W. Zhou, P.M. Ajayan. “Vertical and in-plane heterostructures from WS2/MoS2 monolayers“. Nat. Mater., 2014, 13, 1135-1142.

[22] M.-Y. Li, Y. Shi, C.-C. Cheng, L.-S. Lu, Y.-C. Lin, H.-L. Tang, M.-L. Tsai, C.-W. Chu, K.-H. Wei, J.-H. He, W.-H. Chang, K. Suenaga, L.-J. Li. “Epitaxial growth of a monolayer WSe2-MoS2 lateral p-n junction with an atomically sharp interface.“ Science, 2015, 349, 524-528.

[23] A.M. van der Zande, J. Kunstmann, A. Chernikov, D.A. Chenet, Y. You, X. Zhang, P.Y. Huang, T.C. Berkelbach, L. Wang, F. Zhang, M.S. Hybertsen, D.A. Muller, D.R. Reichman, T.F. Heinz, J.C. Hone. “Tailoring the Electronic Structure in Bilayer Molybdenum Disulfide via Interlayer Twist“. Nano Lett., 2014, 14, 3869-3875.

[24] R. Frisenda, E. Navarro-Moratalla, P. Gant, D. Pérez De Lara, P. Jarillo-Herrero, R.V. Gorbachev. “A. Castellanos-Gomez. “Recent progress in the assembly of nanodevices and van der Waals heterostructures by deterministic placement of 2D materials“. Chem. Soc. Rev., 2018, 47, 53-68.

[25] Y.-H. Lee, X.-Q. Zhang, W. Zhang, M.-T. Chang, C.-T. Lin, K.-D. Chang, Y.-C. Yu, J.T.-W. Wang, C.-S. Chang, L.-J. Li, T.-W. Lin.“ Synthesis of Large-Area MoS2 Atomic Layers with Chemical Vapor Deposition.“ Adv. Mater., 2012, 24, 2320-2325.

[26] K.-K. Liu, W. Zhang, Y.-H. Lee, Y.-C. Lin, M.-T. Chang, C.-Y. Su, C.-S. Chang, H. Li, Y. Shi, H. Zhang, C.-S. Lai, L.-J. Li. “Growth of Large-Area and Highly Crystalline MoS2 Thin Layers on Insulating Substrates.“ Nano Lett., 2012, 12, 1538-1544.

[27] X. Ling, Y.-H. Lee, Y. Lin, W. Fang, L. Yu, M.S. Dresselhaus. “J. Kong, Role of the Seeding Promoter in MoS2 Growth by Chemical Vapor Deposition“. Nano Lett., 2014, 14, 464-472.

[28] X.-Q. Zhang, C.-H. Lin, Y.-W. Tseng, K.-H. Huang, Y.-H. Lee. “Synthesis of Lateral Heterostructures of Semiconducting Atomic Layers.“ Nano Lett., 2015,15, 410-415.

[29] X. Duan, C. Wang, J.C. Shaw, R. Cheng, Y. Chen, H. Li, X. Wu, Y. Tang, Q. Zhang, A. Pan, J. Jiang, R. Yu, Y. Huang, X. Duan. “Lateral epitaxial growth of two-dimensional layered semiconductor heterojunctions“. Nat. Nanotechnol., 2014, 9, 1024-1030.

[30] C. Huang, S. Wu, A.M. Sanchez, J.J.P. Peters, R. Beanland, J.S. Ross, P. Rivera, W. Yao, D.H. Cobden, X. Xu. “Lateral heterojunctions within monolayer MoSe2–WSe2 semiconductors“. Nat. Mater., 2014, 13, 1096-1101.

[31] K.-C. Chiu, K.-H. Huang, C.-A. Chen, Y.-Y. Lai, X.-Q. Zhang, E.-C. Lin, M.-H. Chuang, J.-M. Wu, Y.-H. Lee. “Synthesis of In-Plane Artificial Lattices of Monolayer Multijunctions“. Adv. Mater., 2018, 30, 1704796.

[32] C. Zhang, M.-Y. Li, J. Tersoff, Y. Han, Y. Su, L.-J. Li, D.A. Muller, C.-K. Shih. “Strain distributions and their influence on electronic structures of WSe2–MoS2 laterally strained heterojunctions“. Nat. Nanotechnol., 2018, 13, 152-158.

[33] D. Wong, J. Velasco Jr, L. Ju, J. Lee, S. Kahn, H.-Z. Tsai, C. Germany, T. Taniguchi, K. Watanabe, A. Zettl, F. Wang, M.F. Crommie. “Characterization and manipulation of individual defects in insulating hexagonal boron nitride using scanning tunnelling microscopy“. Nat. Nanotechnol., 2015, 10, 949-953.

[34] C. Zhang, C. Wang, F. Yang, J.-K. Huang, L.-J. Li, W. Yao, W. Ji, C.-K. Shih. “Engineering Point-Defect States in Monolayer Wse2“. ACS Nano, 2019, 13, 1595-1602.

[35] C. Zhang, A. Johnson, C.-L. Hsu, L.-J. Li, C.-K. Shih. “Direct Imaging of Band Profile in Single Layer MoS2 on Graphite: Quasiparticle Energy Gap, Metallic Edge States, and Edge Band Bending.“ Nano Lett., 2014, 14, 2443-2447.

[36] R. Addou, C.M. Smyth, J.-Y. Noh, Y.-C. Lin, Y. Pan, S.M. Eichfeld, S. Fölsch, J.A. Robinson, K. Cho, R.M. Feenstra, R.M. Wallace. “One dimensional metallic edges in atomically thin WSe2 induced by air exposure“. 2D Mater. 2018, 5, 025017.

[37] Y.L. Huang, Y. Chen, W. Zhang, S.Y. Quek, C.-H. Chen, L.-J. Li, W.-T. Hsu, W.-H. Chang, Y.J. Zheng, W. Chen, A.T.S. Wee. “Bandgap tunability at single-layer molybdenum disulphide grain boundaries“. Nat. Commun., 2015, 6, 6298.

[38] S. Barja, S. Wickenburg, Z.-F. Liu, Y. Zhang, H. Ryu, Miguel M. Ugeda, Z. Hussain, Z.-X. Shen, S.-K. Mo, E. Wong, Miquel B. Salmeron, F. Wang, M.F. Crommie, D.F. Ogletree, Jeffrey B. Neaton, A. Weber-Bargioni. “Charge density wave order in 1D mirror twin boundaries of single-layer MoSe2“. Nat. Phys., 2016, 12, 751-756.

[39] J. Xue, J. Sanchez-Yamagishi, D. Bulmash, P. Jacquod, A. Deshpande, K. Watanabe, T. Taniguchi, P. Jarillo-Herrero, B.J. LeRoy. “Scanning tunnelling microscopy and spectroscopy of ultra-flat graphene on hexagonal boron nitride“. Nat. Mater., 2011, 10, 282-285.

[40] R. Decker, Y. Wang, V.W. Brar, W. Regan, H.-Z. Tsai, Q. Wu, W. Gannett, A. Zettl, M.F. Crommie. “Local Electronic Properties of Graphene on a BN Substrate via Scanning Tunneling Microscopy“. Nano Lett., 2011, 11, 2291-2295.


[41] H.M. Hill, A.F. Rigosi, K.T. Rim, G.W. Flynn, T.F. Heinz. “Band Alignment in MoS2/WS2 Transition Metal Dichalcogenide Heterostructures Probed by Scanning Tunneling Microscopy and Spectroscopy“. Nano Lett., 2016, 16, 4831-4837.

[42] C. Zhang, Y. Chen, J.-K. Huang, X. Wu, L.-J. Li, W. Yao, J. Tersoff, C.-K. Shih. “Visualizing band offsets and edge states in bilayer–monolayer transition metal dichalcogenides lateral heterojunction“. Nat. Commun., 2016, 7, 10349.

[43] X. Lin, J.C. Lu, Y. Shao, Y.Y. Zhang, X. Wu, J.B. Pan, L. Gao, S.Y. Zhu, K. Qian, Y.F. Zhang, D.L. Bao, L.F. Li, Y.Q. Wang, Z.L. Liu, J.T. Sun, T. Lei, C. Liu, J.O. Wang, K. Ibrahim, D.N. Leonard, W. Zhou, H.M. Guo, Y.L. Wang, S.X. Du, S.T. Pantelides, H.J. Gao. “Intrinsically patterned two-dimensional materials for selective adsorption of molecules and nanoclusters“. Nat. Mater., 2017, 16, 717-721.

[44] M.M. Ugeda, A.J. Bradley, S.-F. Shi, F.H. da Jornada, Y. Zhang, D.Y. Qiu, W. Ruan, S.-K. Mo, Z. Hussain, Z.-X. Shen, F. Wang, S.G. Louie, M.F. Crommie. “Giant bandgap renormalization and excitonic effects in a monolayer transition metal dichalcogenide semiconductor“. Nat. Mater., 2014, 13, 1091-1095.

[45] J. Shi, M. Liu, J. Wen, X. Ren, X. Zhou, Q. Ji, D. Ma, Y. Zhang, C. Jin, H. Chen, S. Deng, N. Xu, Z. Liu, Y. Zhang. “All Chemical Vapor Deposition Synthesis and Intrinsic Bandgap Observation of MoS2/Graphene Heterostructures“. Adv. Mater., 2015, 27, 7086–7092.

[46] B. Schuler, D.Y. Qiu, S. Refaely-Abramson, C. Kastl, C.T. Chen, S. Barja, R.J. Koch, D.F. Ogletree, S. Aloni, A.M. Schwartzberg, J.B. Neaton, S.G. Louie, A. Weber-Bargioni. “Large Spin-Orbit Splitting of Deep In-Gap Defect States of Engineered Sulfur Vacancies in Monolayer WS2“. Phys. Rev. Lett., 2019, 123, 076801.

[47] Y.L. Huang, Z. Ding, W. Zhang, Y.-H. Chang, Y. Shi, L.-J. Li, Z. Song, Y.J. Zheng, D. Chi, S.Y. Quek, A.T.S. Wee. “Gap States at Low-Angle Grain Boundaries in Monolayer Tungsten Diselenide.“ Nano Lett., 2016, 16, 3682-3688.

[48] M.M. Ugeda, A. Pulkin, S. Tang, H. Ryu, Q. Wu, Y. Zhang, D. Wong, Z. Pedramrazi, A. Martín-Recio, Y. Chen, F. Wang, Z.-X. Shen, S.-K. Mo, O.V. Yazyev, M.F. Crommie. “Observation of topologically protected states at crystalline phase boundaries in single-layer Wse2“. Nat. Commun. 2018, 9, 3401.

[49] J. Hong, Z. Hu, M. Probert, K. Li, D. Lv, X. Yang, L. Gu, N. Mao, Q. Feng, L. Xie, J. Zhang, D. Wu, Z. Zhang, C. Jin, W. Ji, X. Zhang, J. Yuan, Z. Zhang. “Exploring atomic defects in molybdenum disulphide monolayers“. Nat. Commun., 2015, 6, 6293.

[50] W. Zhou, X. Zou, S. Najmaei, Z. Liu, Y. Shi, J. Kong, J. Lou, P.M. Ajayan, B.I. Yakobson, J.-C. Idrobo. “Intrinsic Structural Defects in Monolayer Molybdenum Disulfide“. Nano Letters, 2013, 13, 2615-2622.

[51] H.-P. Komsa, A.V. Krasheninnikov. “Native defects in bulk and monolayer MoS2 from first principles“. Phys. Rev. B, 2015, 91, 125304.

[52] Z. Lin, B.R. Carvalho, E. Kahn, R. Lv, R. Rao, H. Terrones, M.A. Pimenta, M. Terrones. “Defect engineering of two-dimensional transition metal dichalcogenides“. 2D Mater., 2016, 3, 022002.

[53] H. Qiu, T. Xu, Z. Wang, W. Ren, H. Nan, Z. Ni, Q. Chen, S. Yuan, F. Miao, F. Song, G. Long, Y. Shi, L. Sun, J. Wang, X. Wang. “Hopping transport through defect-induced localized states in molybdenum disulphide“. Nat. Commun., 2013, 4, 2642.

[54] J.V. Lauritsen, J. Kibsgaard, S. Helveg, H. Topsøe, B.S. Clausen, E. Lægsgaard, F. Besenbacher. “Size-dependent structure of MoS2 nanocrystals“. Nat. Nanotech., 2007, 2, 53-58.

[55] H. Xu, Z. Ding, C.T. Nai, Y. Bao, F. Cheng, S.J.R. Tan, K.P. Loh. “Controllable Synthesis of 2D and 1D MoS2 Nanostructures on Au Surface“. Adv. Func. Mater., 2017, 27, 1603887.

[56] A. Tuxen, J. Kibsgaard, H. Gøbel, E. Lægsgaard, H. Topsøe, J.V. Lauritsen, F. Besenbacher. “Size Threshold in the Dibenzothiophene Adsorption on MoS2 Nanoclusters“. ACS Nano, 2010, 4, 4677-4682.

[57] G. Li, D. Zhang, Q. Qiao, Y. Yu, D. Peterson, A. Zafar, R. Kumar, S. Curtarolo, F. Hunte, S. Shannon, Y. Zhu, W. Yang, L. Cao. “All The Catalytic Active Sites of MoS2 for Hydrogen Evolution“. J. Am. Chem. Soc., 2016, 138, 16632-16638.

[58] J. Bardeen. “Tunnelling from a Many-Particle Point of View“. Phys. Rev. Lett., 1961, 6, 57-59.

[59] J.P. Ibe, P.P. Bey, S.L. Brandow, R.A. Brizzolara, N.A. Burnham, D.P. DiLella, K.P. Lee, C.R.K. Marrian, R.J. Colton. “On the electrochemical etching of tips for scanning tunneling microscopy“. J. Vac. Sci. Technol. A, 1990, 8, 3570-3575.

[60] I. Horcas, R. Fernández, J.M. Gómez-Rodríguez, J. Colchero, J. Gómez-Herrero, A.M. Baro. “WSXM: A software for scanning probe microscopy and a tool for nanotechnology“. Rev. Sci. Instrum., 2007, 78, 013705.

[61] A. Kuc, N. Zibouche, T. Heine. “Influence of quantum confinement on the electronic structure of the transition metal sulfide TS2.“ Phys. Rev. B, 2011, 83, 245213.

[62] T. Cheiwchanchamnangij, W.R.L. Lambrecht. “Quasiparticle band structure calculation of monolayer, bilayer, and bulk MoS2.“ Phys. Rev. B, 2012, 85, 205302.

[63] J. Pető, T. Ollár, P. Vancsó, Z.I. Popov, G.Z. Magda, G. Dobrik, C. Hwang, P.B. Sorokin, L. Tapasztó. “Spontaneous doping of the basal plane of MoS2 single layers through oxygen substitution under ambient conditions“. Nat. Chem., 2018, 10, 1246-1251.

[64] S. Yuan, R. Roldán, M.I. Katsnelson, F. Guinea. “Effect of point defects on the optical and transport properties of MoS2 and WS2.“ Phys. Rev. B, 2014, 90, 041402.

[65] H. Nan, Z. Wang, W. Wang, Z. Liang, Y. Lu, Q. Chen, D. He, P. Tan, F. Miao, X. Wang, J. Wang, Z. Ni. “Strong Photoluminescence Enhancement of MoS2 through Defect Engineering and Oxygen Bonding“. ACS Nano, 2014, 8, 5738-5745.

[66] C. Ataca, H. Şahin, E. Aktürk, S. Ciraci. “Mechanical and Electronic Properties of MoS2 Nanoribbons and Their Defects“. J. Phys. Chem. C, 2011, 115, 3934-3941.

[67] Z. Ding, Q.-X. Pei, J.-W. Jiang, Y.-W. Zhang. “Manipulating the Thermal Conductivity of Monolayer MoS2 via Lattice Defect and Strain Engineering“. J. Phys. Chem. C, 2015, 119, 16358-16365.

[68] M. Bonilla, S. Kolekar, Y. Ma, H.C. Diaz, V. Kalappattil, R. Das, T. Eggers, H.R. Gutierrez, M.-H. Phan, M. Batzill. “Strong room-temperature ferromagnetism in VSe2 monolayers on van der Waals substrates“. Nat. Nanotechnol., 2018, 13, 289-293.

[69] N. Gao, Y. Guo, S. Zhou, Y. Bai, J. Zhao. “Structures and Magnetic Properties of MoS2 Grain Boundaries with Antisite Defects“. J. Phys. Chem. C, 2017, 121, 12261-12269.

[70] J.H. Park, A. Sanne, Y. Guo, M. Amani, K. Zhang, H.C.P. Movva, J.A. Robinson, A. Javey, J. Robertson, S.K. Banerjee, A.C. Kummel. “Defect passivation of transition metal dichalcogenides via a charge transfer van der Waals interface“. Sci. Adv., 2017, 3, e1701661.

[71] M.V. Bollinger, J.V. Lauritsen, K.W. Jacobsen, J.K. Nørskov, S. Helveg, F. Besenbacher. “One-Dimensional Metallic Edge States in MoS2“. Phys. Rev. Lett., 2001, 87, 196803.

[72] M.V. Bollinger, K.W. Jacobsen, J.K. Nørskov. “Atomic and electronic structure of MoS2 nanoparticles“. Phys. Rev. B, 2003, 67, 085410.

[73] R.-L. Chu, G.-B. Liu, W. Yao, X. Xu, D. Xiao, C. Zhang. “Spin-orbit-coupled quantum wires and Majorana fermions on zigzag edges of monolayer transition-metal dichalcogenides“. Phys. Rev. B, 2014, 89, 155317.

[74] S. Kc, R.C. Longo, R. Addou, R.M. Wallace, K. Cho. “Impact of intrinsic atomic defects on the electronic structure of MoS2 monolayers“. Nanotechnology, 2014, 25, 375703.
[75] Z. Lin, B.R. Carvalho, E. Kahn, R. Lv, R. Rao, H. Terrones, M.A. Pimenta, M. Terrones. “Defect engineering of two-dimensional transition metal dichalcogenides“. 2D Mater., 2016, 3 022002.

[76] H. Qiu, T. Xu, Z. Wang, W. Ren, H. Nan, Z. Ni, Q. Chen, S. Yuan, F. Miao, F. Song, G. Long, Y. Shi, L. Sun, J. Wang, X. Wang. “Hopping transport through defect-induced localized states in molybdenum disulphide“. Nat. Commun., 2013, 4, 2642.

[77] J.-Y. Noh, H. Kim, Y.-S. Kim. “Stability and electronic structures of native defects in single-layer MoS¬2“. Phys. Rev. B, 2014, 89, 205417.

[78] H.S. Wong, C. Durkan. “Unraveling the rotational disorder of graphene layers in graphite.“ Phys. Rev. B, 2010, 81, 045403.

[79] K. Chen, X. Wan, J. Wen, W. Xie, Z. Kang, X. Zeng, H. Chen, J.-B. Xu. “Electronic Properties of MoS2–WS2 Heterostructures Synthesized with Two-Step Lateral Epitaxial Strategy“. ACS Nano, 2015, 9, 9868-9876.

[80] M.-L. Tsai, M.-Y. Li, J.R.D. Retamal, K.-T. Lam, Y.-C. Lin, K. Suenaga, L.-J. Chen, G. Liang, L.-J. Li, J.-H. He. “Single Atomically Sharp Lateral Monolayer p-n Heterojunction Solar Cells with Extraordinarily High Power Conversion Efficiency“. Adv. Mater., 2017, 29, 1701168.

[81] L. Liu, J. Park, D.A. Siegel, K.F. McCarty, K.W. Clark, W. Deng, L. Basile, J.C. Idrobo, A.-P. Li, G. Gu. “Heteroepitaxial Growth of Two-Dimensional Hexagonal Boron Nitride Templated by Graphene Edges“. Science, 2014, 343, 163-167.

[82] D.A. Cosma, J.R. Wallbank, V. Cheianov. V.I. Fal'ko. “Moiré pattern as a magnifying glass for strain and dislocations in van der Waals heterostructures“. Faraday Discuss., 2014, 173, 137-143.

[83] Y. Jiang, J. Mao, J. Duan, X. Lai, K. Watanabe, T. Taniguchi, E.Y. Andrei. “Visualizing Strain-Induced Pseudomagnetic Fields in Graphene through an hBN Magnifying Glass“. Nano Lett., 2017, 17, 2839-2843.