二维半导体及其异质结的电子学和边缘重构研究

寻求超越传统硅基器件的半导体材料，有利于解决我国在芯片领域的卡脖子问题。欧洲微电子研究中心（IMEC）在2020年指出，在芯片进一步小型化的道路上，除了二维材料别无选择。二维材料因其柔性、超薄、无表面悬键、层数可调等优点，展示出在（光、自旋）电子器件领域的潜在应用。然而，二维材料在实际应用中也面临一些挑战。一方面，实际制备的二维材料，总会存在边界或边缘（可类比于三维材料的表面）。边界的存在会极大地改变和影响二维半导体材料的本征性质，如半导体-金属转变、带隙减小或关闭、边界磁性、电荷密度波和自旋密度波等。另一方面，二维半导体和金属电极形成异质结用于电子器件时，在金属-半导体界面处会产生接触电阻，接触电阻大和缺少p型接触是典型二维半导体（MoS₂）器件应用中所面临的严峻问题。

本论文通过理论分析和模拟计算，揭示出新型二维材料MSi₂N₄的单层及异质结在自旋（光）电子器件中的应用潜力；针对合成MSi₂N₄和TMDCs家族时的边缘重构问题，给出了新的重构模型和对重构机理更深刻的微观物理解释；最后，为了促进二维材料在互补逻辑器件中的应用，提出一种降低金属-MoS₂结p型肖特基势垒的新方法，并实现欧姆接触。具体如下：

首先，研究了单层H相和T相MSi₂N₄（M=Ti，Zr，Hf，V，Nb，Ta, Cr，Mo，W）的电子结构，通过晶体场和交换场引起的d能级劈裂以及电子轨道填充来理解不同单层的电子结构。基于第V-B族（M=V，Nb，Ta）单层和异质结展示出的丰富电子性质（如磁性半金属、磁性半导体和双极磁性半导体等，并且具有高的居里温度），模拟了在自旋电子器件方面的应用。MSi₂N₄半导体组成的异质结的能带排布类型和动量空间匹配，展示出在光电子器件方面的应用潜力。这一部分的研究揭示了MSi₂N₄家族在高温（室温）自旋（光）电子器件方面的应用潜力。

其次，研究了MoSi₂N₄单层两种典型边界（扶手椅形和锯齿形纳米带）的本征性质，探究了锯齿形纳米带的边缘重构及重构后对金属化和电子结构的影响，提出3倍单胞的N重构模型可以打开一个小的带隙。这一部分的研究建立了MoSi₂N₄边缘重构的理论基础和重构模型。

再次，为进一步理解边缘重构微观机理，针对实验和理论上已有大量数据和模型可参考的H-MoX₂（X=S，Se）锯齿形纳米带Mo边缘的重构进行了深入研究。分析了常规的电子计数规则在边缘重构上的不足，并采用不同的赝氢钝化模型研究边缘重构机理。提出了新的边缘重构机制，即：边缘上的原子不仅发生结构重构，也会发生电子重构，尤其是价态的升高和降低。提出新的重构模型，其边缘带隙数值与相关实验测量到的边缘带隙大小相当，验证了新模型的合理性。

最后，针对二维半导体用于电子器件的瓶颈问题（金属-半导体结界面电阻），初步研究了降低金属-半导体结接触电阻的方法，提出采用具有较弱金属性的二元化合物（CuS）作为电极与典型二维半导体材料（MoS₂）连接。模拟了不同的CuS表面与MoS₂的接触类型，发现CuS不同表面可分别实现n型和p型欧姆接触，并对p型肖特基势垒公式进行了修正，为以后的p型欧姆连接实验提供了理论基础和新的设计思路。

[1] Sri S. Towards atomic channels and deconstructed chips [EB/OL]. (2021-01-12)
[2023-04-18]. http://community.cadence.com/cadence_blogs_8/b/breakfast-bytes/posts/iedm20-1.
[2] Shen P. C., Su C., Lin Y. X., Chou A. S., Cheng C. C., Park J. H., Chiu M. H., Lu A. Y., Tang H. L., Tavakoli M. M., Pitner G., Ji X., Cai Z. Y., Mao N. N., Wang J. T., Tung V., Li J., Bokor J., Zettl A., Wu C. I., Palacios T., Li L. J., Kong J. Ultralow contact resistance between semimetal and monolayer semiconductors [J]. Nature, 2021, 593(7858): 211-217.
[3] Chen T. A., Chuu C. P., Tseng C. C., Wen C. K., Wong H. S. Philip, Pan S. Y., Li R. T., Chao T. A., Chueh W. C., Zhang Y. F., Fu Q., Yakobson B. I., Chang W. H., Li L. J. Wafer-scale single-crystal hexagonal boron nitride monolayers on Cu (111) [J]. Nature, 2020, 579(7798): 219-223.
[4] Novoselov K. S., Geim A. K., Morozov S. V., Jiang D., Zhang Y., Dubonos S. V., Grigorieva I. V., Firsov A. A. Electric field effect in atomically thin carbon films [J]. Science, 2004, 306(5696): 666-669.
[5] Zhang H. Ultrathin two-dimensional nanomaterials [J]. ACS Nano, 2015, 9(10): 9451-9469.
[6] Liu C. C., Feng W. X., Yao Y. G. Quantum spin hall effect in silicene and two-dimensional germanium [J]. Physical Review Letters, 2011, 107(7): 076802.
[7] Liu C. C., Jiang H., Yao Y. G. Low-energy effective Hamiltonian involving spin-orbit coupling in silicene and two-dimensional germanium and tin [J]. Physical Review B, 2011, 84(19): 195430.
[8] Osada M., Sasaki T. Two-dimensional dielectric nanosheets: novel nano-electronics from nanocrystal building blocks [J]. Advanced Materials, 2012, 24(2): 210-228.
[9] Wang Q. H., Kourosh K. Z., Kis A., Coleman J. N., Strano M. S. Electronics and optoelectronics of two-dimensional transition metal dichalcogenides [J]. Nature Nanotechnology, 2012, 7(11): 699-712.
[10] Dean C. R., Young A. F., Meric I., Lee C., Wang L., Sorgenfrei S., Watanabe K., Taniguchi T., Kim P., Shepard K. L., Hone J. Boron nitride substrates for high-quality graphene electronics [J]. Nature Nanotechnology, 2010, 5(10): 722-726.
[11] Knobloch T., Illarionov Y. Y., Ducry F., Schleich C., Wachter S., Watanabe K., Taniguchi T., Mueller T., Waltl M., Lanza M., Vexler M. I., Luisier M., Grasser T. The performance limits of hexagonal boron nitride as an insulator for scaled CMOS devices based on two-dimensional materials [J]. Nature Electronics, 2021, 4(2): 98-108.
[12] Kim B. K., Kim T. H., Choi D. H., Kim H., Watanabe K., Taniguchi T., Rho H., Kim J. J., Kim Y. H., Bae M. H. Origins of genuine Ohmic van der Waals contact between indium and MoS2 [J]. npj 2D Materials and Applications, 2021, 5(1): 9.
[13] Petkov V., Ren Y. T. Local structure memory effects in the polar and nonpolar phases of MoTe2 [J]. Physical Review B, 2021, 103(9): 094101.
[14] Chege S., Ning’i P., Sifuna J., Amolo G. O. Origin of band inversion in topological Bi2Se3 [J]. AIP Advances, 2020, 10(9): 095018.
[15] Zhang E., Xu X., Zou Y., Ai L. F., Dong X., Huang C., Leng P. L., Liu S. Q., Zhang Y., Jia Z. H., Peng X. Y., Zhao M. H., Yang Y. K., Li Z. H., Guo H. W., Haigh S., Nagaosa N., Shen J., Xiu F. Nonreciprocal superconducting NbSe2 antenna [J]. Nature Communications, 2020, 11(1): 5634.
[16] Sahoo D., Senapati S., Naik R. Progress and prospects of 2D VS2 transition metal dichalcogenides [J]. FlatChem, 2022, 36(10): 100455.
[17] Kang J. H., Liu W., Sarkar D., Jena D., Banerjee K. Computational study of metal contacts to monolayer transition-metal dichalcogenide semiconductors [J]. Physical Review X, 2014, 4(3): 031005.
[18] Geim A. K., Novoselov K. S. The rise of graphene [J]. Nature Materials, 2007, 6(3): 183-191.
[19] Meyer J. C., Geim A. K., Katsnelson M. I., Novoselov K. S., Booth T. J., Roth S. The structure of suspended graphene sheets [J]. Nature, 2007, 446(7131): 60-63.
[20] Novoselov K. S. Discovery of 2D van der Waals layered MoSi2N4 family [J]. National Science Review, 2020, 7(12): 1842-1844.
[21] Castro Neto A. H., Guinea F., Peres N. M. R., Novoselov K. S., Geim A. K. The electronic properties of graphene [J]. Reviews of Modern Physics, 2009, 81(1): 109-162.
[22] Zhu Y. W., Murali S., Cai W. W., Li X. S., Suk J. W., Potts J. R., Ruoff R. S. Graphene and graphene oxide: synthesis, properties, and applications [J]. Advanced Materials, 2010, 22(35): 3906-3924.
[23] Li L. K., Yu Y. J., Ye G. J., Ge Q. Q., Ou X. D., Wu H., Feng D. L., Chen X. H., Zhang Y. B. Black phosphorus field-effect transistors [J]. Nature Nanotechnology, 2014, 9(5): 372-377.
[24] Churchill H. O. H., Pablo J. H. Phosphorus joins the family [J]. Nature Nanotechnology, 2014, 9(5): 330-331.
[25] Zhu J. X. , Liu X. D., Xue M. Z., Chen C. X. Phosphorene: Synthesis, structure, properties and device applications [J]. Acta Physico-Chimica Sinica, 2017, 33(11): 2153-2172.
[26] Scotognella F., Kriegel I., Sassolini S. Covalent functionalized black phosphorus quantum dots [J]. Optical Materials, 2018, 75(10): 521-524.
[27] Li X. F., Zhang Z. F., Gao T. T., Shi X. H., Gu C. R., Wu Y. Q. Van der Waals epitaxial trilayer MoS2 crystals for high-speed electronics [J]. Advanced Functional Materials, 2022, 32(46): 2208091.
[28] Voiry D., Mohite A., Chhowalla M. Phase engineering of transition metal dichalcogenides [J]. Chemical Society Reviews, 2015, 44(9): 2702-2712.
[29] Lv X. H., Wu M. Q., Ren Y. T., Wang R. N., Zhang H., Jin C. D., Lian R. Q., Gong P. L., Shi X. Q., Wang J. L. Hole- and electron-injection driven phase transitions in transition metal dichalcogenides and beyond: A unified understanding [J]. Physical Review B, 2022, 105(2): 024108.
[30] Tan C. L., Zhang H. Two-dimensional transition metal dichalcogenide nanosheet-based composites [J]. Chemical Society Reviews, 2015, 44(9): 2713-2731.
[31] Mak K. F., Lee C. G., Hone J., Shan J., Heinz T. F. Atomically thin MoS2: A new direct-gap semiconductor [J]. Physical Review Letters, 2010, 105(13): 136805.
[32] Splendiani A., Sun L. , Zhang Y. B., Li T., Kim J. W., Chim C. Y., Galli G. L., Wang F. Emerging photoluminescence in monolayer MoS2 [J]. Nano Letters, 2010, 10(4): 1271-1275.
[33] Li Y. Z., Xu H. Y., Liu W. Z., Yang G. C., Shi J., Liu Z., Liu X. F., Wang Z. Q., Tang Q. X., Liu Y. C. Enhancement of exciton emission from multilayer MoS2 at high temperatures: Intervalley transfer versus interlayer decoupling [J]. Small, 2017, 13(17): 1700157.
[34] Hong Y. L., Liu Z. B., Wang L., Zhou T. Y., Ma W., Xu C., Feng S., Chen L., Chen M. L., Sun D. M., Chen X. Q., Cheng H. M., Ren W. C. Chemical vapor deposition of layered two-dimensional MoSi2N4 materials [J]. Science, 2020, 369(6504): 670-674.
[35] Wang Q. Q., Cao L. M., Liang S. J., Wu W. K., Wang G. Z., Lee C. H., Ong W. L., Yang H. Y., Ang L. K., Yang S. Y., Ang Y. S. Efficient Ohmic contacts and built-in atomic sublayer protection in MoSi2N4 and WSi2N4 monolayers [J]. npj 2D Materials and Applications, 2021, 5(1): 71.
[36] Wang L., Shi Y. P., Liu M. F., Zhang A., Hong Y. L., Li R. H., Gao Q., Chen M. X., Ren W. C., Cheng H. M., Li Y. Y., Chen X. Q. Intercalated architecture of MA2Z4 family layered van der Waals materials with emerging topological, magnetic and superconducting properties [J]. Nature Communications, 2021, 12(1): 2361.
[37] Cao L. M., Zhou G. H., Wang Q. Q., Ang L. K., Ang Y. S. Two-dimensional van der Waals electrical contact to monolayer MoSi2N4 [J]. Applied Physics Letters, 2021, 118(1): 013106.
[38] Guo S. D., Zhu Y. T., Mu W. Q., Wang L., Chen X. Q. Structure effect on intrinsic piezoelectricity in septuple-atomic-layer MSi2N4 (M=Mo and W) [J]. Computational Materials Science, 2021, 188(10): 110223.
[39] Guo S. D., Zhu Y. T., Mu W. Q., Ren W. C. Intrinsic piezoelectricity in monolayer MSi2N4 (M=Mo, W, Cr, Ti, Zr and Hf) [J]. Europhysics Letters, 2020, 132(5): 57002.
[40] Guo S. D., Mu W. Q., Zhu Y. T., Han R. Y., Ren W. C. Predicted septuple-atomic-layer Janus MSiGeN4 (M=Mo and W) monolayers with Rashba spin splitting and high electron carrier mobilities [J]. Journal of Materials Chemistry C, 2021, 9(7): 2464-2473.
[41] Kang L., Lin Z. S. Second harmonic generation of MoSi2N4-type layers [J]. Physical Review B, 2021, 103(19): 195404.
[42] Ding Y., Wang Y. L. Computational exploration of stable 4d/5d transition-metal MSi2N4 (M=Y-Cd and Hf-Hg) nanosheets and their versatile electronic and magnetic properties [J]. The Journal of Physical Chemistry C, 2021, 125(35): 19580-19591.
[43] Yang C., Song Z. G., Sun X. T., Lu J. Valley pseudospin in monolayer MoSi2N4 and MoSi2As4 [J]. Physical Review B, 2021, 103(3): 035308.
[44] Cui Q. R., Zhu Y. M., Liang J. H., Cui P., Yang H. X. Spin-valley coupling in a two-dimensional VSi2N4 monolayer [J]. Physical Review B, 2021, 103(8): 085421.
[45] Li Si, Wang Q. Q., Zhang C. M., Guo P., Yang S. Y. Correlation-driven topological and valley states in monolayer VSi2P4 [J]. Physical Review B, 2021, 104(8): 085149.
[46] Zhong H. X., Xiong W. Q., Lv P. F., Yu J., Yuan S. J. Strain-induced semiconductor to metal transition in MA2Z4 bilayers (M=Ti, Cr, Mo; A=Si; Z=N, P) [J]. Physical Review B, 2021, 103(8): 085124.
[47] Zang Y. M., Wu Q., Du W. H., Dai Y., Huang B. B., Ma Y. D. Activating electrocatalytic hydrogen evolution performance of two-dimensional MSi2N4 (M=Mo, W): A theoretical prediction [J]. Physical Review Materials, 2021, 5(4): 045801.
[48] Tian M., Wei C. H., Zhang J. L., Wang J., Yang R. Z. Electronic, optical, and water solubility properties of two-dimensional layered SnSi2N4 from first principles [J]. Physical Review B, 2021, 103(19): 195305.
[49] Zhou X. D., Zhang R. W., Zhang Z. Y., Feng W. X., Mokrousov Y., Yao Y. G. Sign-reversible valley-dependent Berry phase effects in 2D valley-half-semiconductors [J]. npj Computational Materials, 2021, 7(1): 160.
[50] Wu Q. Y., Cao L. M., Ang Y. S., Ang L. K. Semiconductor-to-metal transition in bilayer MoSi2N4 and WSi2N4 with strain and electric field [J]. Applied Physics Letters, 2021, 118(11): 113102.
[51] Zhou L. X., Ren Y. T., Chen Y. T., Lv X. H., Jin C. D., Zhang H., Gong P. L., Lian R. Q., Wang R. N., Wang J. L., Shi X. Q. Quasi-bonding-induced gap states in metal/two-dimensional semiconductor junctions: Route for Schottky barrier height reduction [J]. Physical Review B, 2022, 105(22): 224105.
[52] Luo R. C., Xu W. W., Zhang Y. Z., Wang Z. Q., Wang X. D., Gao Y., Liu P., Chen M. W. Van der Waals interfacial reconstruction in monolayer transition-metal dichalcogenides and gold heterojunctions [J]. Nature Communications, 2020, 11(1): 1011.
[53] Liu Y., Shang X., Zhuang J., Li D., Cui T. Recent progress in the edge reconstruction of two-dimensional materials [J]. Journal of Physics D: Applied Physics, 2022, 55(41): 414003.
[54] Helveg S., Lauritsen J. V., Lægsgaard E., Stensgaard I., Nørskov J. K., Clausen B. S., Topsøe H., Besenbacher F. Atomic-scale structure of single-layer MoS2 nanoclusters [J]. Physical Review Letters, 2000, 84(5): 951-954.
[55] Chen Y. X., Cui P., Ren X. B., Zhang C. D., Jin C. H., Zhang Z. Y., Shih C. K. Fabrication of MoSe2 nanoribbons via an unusual morphological phase transition [J]. Nature Communications, 2017, 8(1): 15135.
[56] Zhao X. X., Fu D., Ding Z. J., Zhang Y. Y., Wan D. Y., Tan J. R., Chen Z. X., Leng K., Dan J. D., Fu W., Geng D. C., Song P., Du Y. H., Venkatesan T., Pantelides Sokrates T., Pennycook Stephen J., Zhou W., Loh K. P. Mo-terminated edge reconstructions in nanoporous molybdenum disulfide film [J]. Nano Letters, 2018, 18(1): 482-490.
[57] Cheng F., Xu H., Xu W. T., Zhou P. J., Martin J., Loh K. P. Controlled growth of 1D MoSe2 nanoribbons with spatially modulated edge states [J]. Nano Letters, 2017, 17(2): 1116-1120.
[58] Bollinger M. V., Lauritsen J. V., Jacobsen K. W., Nørskov J. K., Helveg S., Besenbacher F. One-dimensional metallic edge states in MoS2 [J]. Physical Review Letters, 2001, 87(19): 196803.
[59] Lucking M. C., Bang J., Terrones H., Sun Y. Y., Zhang S. B. Multivalency-induced band gap opening at MoS2 edges [J]. Chemistry of Materials, 2015, 27(9): 3326-3331.
[60] Davelou D., Kopidakis G., Kaxiras E., Remediakis I. N. Nanoribbon edges of transition-metal dichalcogenides: Stability and electronic properties [J]. Physical Review B, 2017, 96(16): 165436.
[61] Hu G. X., Fung V., Sang X. H., Unocic R. R., Ganesh P. Predicting synthesizable multi-functional edge reconstructions in two-dimensional transition metal dichalcogenides [J]. npj Computational Materials, 2020, 6(1): 44.
[62] Yuman S. A., Ewels C. P. Stability, structure and reconstruction of 1H-edges in MoS2 [J]. Chemistry-A European Journal, 2020, 26(29): 6686-6693.
[63] Güller F., Llois A. M., Goniakowski J., Noguera C. Prediction of structural and metal-to-semiconductor phase transitions in nanoscale MoS2, WS2, and other transition metal dichalcogenide zigzag ribbons [J]. Physical Review B, 2015, 91(7): 075407.
[64] Li Y. F., Zhou Z., Zhang S. B., Chen Z. F. MoS2 nanoribbons: High stability and unusual electronic and magnetic properties [J]. Journal of the American Chemical Society, 2008, 130(49): 16739-16744.
[65] Cui P., Choi J. H., Chen W., Zeng J., Shih C. K., Li Z. Y., Zhang Z. Y. Contrasting structural reconstructions, electronic properties, and magnetic orderings along different edges of zigzag transition metal dichalcogenide nanoribbons [J]. Nano Letters, 2017, 17(2): 1097-1101.
[66] Cui P., Zeng J., Peng H. W., Choi J. H., Li Z. Y., Zeng C. G., Shih C. K., Perdew J. P., Zhang Z. Y. Predictive design of intrinsic half-metallicity in zigzag tungsten dichalcogenide nanoribbons [J]. Physical Review B, 2019, 100(19): 195304.
[67] Deng X. H., Li Z. Y., Yang J. L. One-dimensional magnetic order stabilized in edge-reconstructed MoS2 nanoribbon via bias voltage [J]. The Journal of Physical Chemistry Letters, 2020, 11(18): 7531-7535.
[68] Cao D., Shen T., Liang P., Chen X. S., Shu H. B. Role of chemical potential in flake shape and edge properties of monolayer MoS2 [J]. The Journal of Physical Chemistry C, 2015, 119(8): 4294-4301.
[69] Deng Q. M., Thi Q. H., Zhao J., Yun S. J., Kim H., Chen G., Ly T. H. Impact of polar edge terminations of the transition metal dichalcogenide monolayers during vapor growth [J]. The Journal of Physical Chemistry C, 2018, 122(6): 3575-3581.
[70] Li D., Ding F. Environment-dependent edge reconstruction of transition metal dichalcogenides: A global search [J]. Materials Today Advances, 2020, 8(10): 100079.
[71] Chen K. Y., Deng J. K., Ding X. D., Sun J., Yang S., Liu J. Z. Ferromagnetism of 1T′-MoS2 nanoribbons stabilized by edge reconstruction and its periodic variation on nanoribbons width [J]. Journal of the American Chemical Society, 2018, 140(47): 16206-16212.
[72] Liu Y. Y., Stradins P., Wei S. H. Van der Waals metal-semiconductor junction: Weak Fermi level pinning enables effective tuning of Schottky barrier [J]. Science Advances, 2016, 2(10): e1600069.
[73] Tran R., Li X. G., Montoya J. H., Winston D., Persson K., Ong S. P. Anisotropic work function of elemental crystals [J]. Surface Science, 2019, 687(6): 48-55.
[74] Chou A. S., Cheng C. C., Liew S. L., Ho P. H., Wang S. Y., Chang Y. C., Chang C. K., Su Y. C., Huang Z. D., Fu F. Y., Hsu C. F., Chung Y. Y., Chang W. H., Li L. J., Wu C. I. High on-state current in chemical vapor deposited monolayer MoS2 nFETs with Sn Ohmic contacts [J]. IEEE Electron Device Letters, 2021, 42(2): 272-275.
[75] Wang Q., Deng B., Shi X. Q. A new insight for ohmic contacts to MoS2: By tuning MoS2 affinity energies but not metal work-functions [J]. Physical Chemistry Chemical Physics, 2017, 19(38): 26151-26157.
[76] Wang Q., Shao Y. F., Gong P. L., Shi X. Q. Metal–2D multilayered semiconductor junctions: Layer number dependent Fermi-level pinning [J]. Journal of Materials Chemistry C, 2020, 8(9): 3113-3119.
[77] Sutcliffe B. T., Woolley R. G. On the quantum theory of molecules [J]. The Journal of Chemical Physics, 2012, 137(22): 22544.
[78] Hartree D. R. The wave mechanics of an atom with a non-Coulomb central field. part III. term values and intensities in series in optical spectra [J]. Mathematical Proceedings of the Cambridge Philosophical Society, 1928, 24(6): 426 - 437.
[79] Slater J. C. A simplification of the Hartree-Fock method [J]. Physical Review, 1951, 81(3): 385-390.
[80] Thomas L. H. The calculation of atomic fields [J]. Mathematical Proceedings of the Cambridge Philosophical Society, 2008, 23(5): 542-548.
[81] Hohenberg P., Kohn W. Inhomogeneous electron gas [J]. Physical Review, 1964, 136(3B): B864-B871.
[82] Kohn W., Sham L. J. Self-consistent equations including exchange and correlation effects [J]. Physical Review, 1965, 140(4A): A1133-A1138.
[83] Perdew J. P., Burke K., Ernzerhof M. Generalized gradient approximation made simple [J]. Physical Review Letters, 1996, 77(18): 3865-3868.
[84] Perdew J. P., Chevary J. A., Vosko S. H., Jackson K. A., Pederson M. R., Singh D. J., Fiolhais C. Atoms, molecules, solids, and surfaces: Applications of the generalized gradient approximation for exchange and correlation [J]. Physical Review B, 1992, 46(11): 6671-6687.
[85] Paier J., Marsman M., Hummer K., Kresse G., Gerber I. C., Ángyán J. G. Screened hybrid density functionals applied to solids [J]. The Journal of Chemical Physics, 2006, 124(15): 154709.
[86] Hamann D. R., Schlüter M., Chiang C. Norm-conserving pseudopotentials [J]. Physical Review Letters, 1979, 43(20): 1494-1497.
[87] Vanderbilt D. Soft self-consistent pseudopotentials in a generalized eigenvalue formalism [J]. Physical Review B, 1990, 41(11): 7892-7895.
[88] Blöchl P. E. Projector augmented-wave method [J]. Physical Review B: Condens Matter, 1994, 50(24): 17953-17979.
[89] Kresse G., Joubert D. From ultrasoft pseudopotentials to the projector augmented-wave method [J]. Physical Review B, 1999, 59(3): 1758-1775.
[90] Hafner J. Ab-initio simulations of materials using VASP: Density-functional theory and beyond [J]. Journal of Computational Chemistry, 2008, 29(13): 2044-2078.
[91] Kresse G., Furthmüller J. Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis [J]. Physical Review B, 1996, 54(16): 11169-11186.
[92] Giannozzi P., Baroni S., Bonini N., Calandra M., Car R., Cavazzoni C., Ceresoli D., Chiarotti G. L. QUANTUM ESPRESSO: a modular and open-source software project for quantum simulations of materials [J]. Journal of Physics: Condensed Matter, 2009, 21(39): 395502.
[93] Momma K., Izumi F. VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data [J]. Journal of Applied Crystallography, 2011, 44(6): 1272-1276.
[94] Krishnamurthi S., Farmanbar M., Brocks G. One-dimensional electronic instabilities at the edges of MoS2 [J]. Physical Review B, 2020, 102(16): 165142.
[95] Togo A., Tanaka I. First principles phonon calculations in materials science [J]. Scripta Materialia, 2015, 108(6): 1-5.
[96] Ding Y., Wang Y. L. Density functional theory study of the silicene-like SiX and XSi3 (X=B, C, N, Al, P) honeycomb lattices: The various buckled structures and versatile electronic properties [J]. The Journal of Physical Chemistry C, 2013, 117(35): 18266-18278.
[97] Dudarev S. L., Botton G. A., Savrasov S. Y., Humphreys C. J., Sutton A. P. Electron-energy-loss spectra and the structural stability of nickel oxide: An LSDA+U study [J]. Physical Review B, 1998, 57(3): 1505-1509.
[98] Wang V., Xu N., Liu J. C., Tang G., Geng W. T. VASPKIT: A user-friendly interface facilitating high-throughput computing and analysis using VASP code [J]. Computer Physics Communications, 2021, 267(6): 108033.
[99] Thakuria N., Schulman D., Das S., Gupta S. K. 2D strain FET (2D-SFET) based SRAMs-part I: Device-circuit Interactions [J]. IEEE Transactions on Electron Devices, 2020, 67(11): 4866-4874.
[100] Thakuria N., Schulman D., Das S., Gupta S. K. 2D strain FET (2D-SFET)-based SRAMs-part II: Back voltage-enabled designs [J]. IEEE Transactions on Electron Devices, 2020, 67(11): 4875-4883.
[101] Quhe R. G., Xu L., Liu S. Q., Yang C. , Wang Y. Y., Li H., Yang J., Li Q. H., Shi B., Li Y., Pan Y. Y., Sun X. T., Li J. Z., Weng M. Y., Zhang H., Guo Y., Xu L. Q., Tang H., Dong J. C., Yang J. B., Zhang Z. Y., Lei M., Pan F., Lu J. Sub-10 nm two-dimensional transistors: Theory and experiment [J]. Physics Reports, 2021, 938(6): 1-72.
[102] Wolf S. A., Awschalom D. D., Buhrman R. A., Daughton J. M., Von Molnár S., Roukes M. L., Chtchelkanova A. Y., Treger D. M. Spintronics: A spin-based electronics vision for the future [J]. Science, 2001, 294(5546): 1488.
[103] Li X. X., Yang J. L. First-principles design of spintronics materials [J]. National Science Review, 2016, 3(3): 365-381.
[104] Gong C., Li L., Li Z. L., Ji H. W., Stern A., Xia Y., Cao T., Bao W., Wang C. Z., Wang Y., Qiu Z. Q., Cava R. J., L. Steven G., Xia J., Zhang X. Discovery of intrinsic ferromagnetism in two-dimensional van der Waals crystals [J]. Nature, 2017, 546(7657): 265-269.
[105] Lee J. U., Lee S. M., Ryoo J. H., Kang S. M., Kim T. Y., Kim P., Park C. H., Park J. G., Cheong H. Ising-type magnetic ordering in atomically thin FePS3 [J]. Nano Letters, 2016, 16(12): 7433-7438.
[106] Huang B. , Clark G., Navarro M., Klein D. R., Cheng R., Seyler K. L., Zhong D., Schmidgall E., Mcguire M. A., Cobden D. H., Yao W., Xiao D., Pablo J. H., Xu X. D. Layer-dependent ferromagnetism in a van der Waals crystal down to the monolayer limit [J]. Nature, 2017, 546(7657): 270-273.
[107] Bonilla M., Kolekar S., Ma Y. D., Diaz H. C., Kalappattil V., Das R., Eggers T., Gutierrez H. R., Phan M. H., Batzill M. Strong room-temperature ferromagnetism in VSe2 monolayers on van der Waals substrates [J]. Nature Nanotechnology, 2018, 13(4): 289-293.
[108] Ma Y. D., Dai Y., Guo M., Niu C. W., Zhu Y. T., Huang B. B. Evidence of the existence of magnetism in pristine VX2 monolayers (X=S, Se) and their strain-induced tunable magnetic properties [J]. ACS Nano, 2012, 6(2): 1695-1701.
[109] Zhuang H. L., H. Richard G. Stability and magnetism of strongly correlated single-layer VS2 [J]. Physical Review B, 2016, 93(5): 054429.
[110] Zhang F., Kong Y. C., Pang R., Hu L., Gong P. L., Shi X. Q., Tang Z. K. Super-exchange theory for polyvalent anion magnets [J]. New Journal of Physics, 2019, 21(5): 053033.
[111] Ren Y. T., Hu L., Shao Y. F., Hu Y. J., Huang L., Shi X. Q. Magnetism of elemental two-dimensional metals [J]. Journal of Materials Chemistry C, 2021, 9(13): 4554-4561.
[112] Li L. F., Wang Y. L., Xie S. G., Li X. B., Wang Y. Q., Wu R. T., Sun H. B., Zhang S. B., Gao H. J. Two-dimensional transition metal honeycomb realized: Hf on Ir(111) [J]. Nano Letters, 2013, 13(10): 4671-4674.
[113] Zhao J., Deng Q. M., Bachmatiuk A., Sandeep G., Popov A., Eckert J., Rümmeli M. H. Free-standing single-atom-thick iron membranes suspended in graphene pores [J]. Science, 2014, 343(6176): 1228.
[114] Grimme S. Semiempirical GGA-type density functional constructed with a long-range dispersion correction [J]. Journal of Computational Chemistry, 2006, 27(15): 1787-1799.
[115] Yan S. M., Qiao W., He X. M., Guo X. B., Xi L., Zhong W., Du Y. W. Enhancement of magnetism by structural phase transition in MoS2 [J]. Applied Physics Letters, 2015, 106(1): 012408.
[116] Andrew R. C., Mapasha R. E., Ukpong A. M., Chetty N. Mechanical properties of graphene and boronitrene [J]. Physical Review B, 2012, 85(12): 125428.
[117] Yang J. S., Zhao L. Z., Li S. Q., Liu H. S., Wang L., Chen M. D., Gao J. F., Zhao J. J. Accurate electronic properties and non-linear optical response of two-dimensional MA2Z4 [J]. Nanoscale, 2021, 13(10): 5479-5488.
[118] Enyashin A. N., Yadgarov L., Houben L., Popov I., Weidenbach M., Tenne R., Bar M., Seifert G. New route for stabilization of 1T-WS2 and MoS2 phases [J]. The Journal of Physical Chemistry C, 2011, 115(50): 24586-24591.
[119] Kang Y. M., Najmaei S., Liu Z., Bao Y. J., Wang Y. M., Zhu X., Halas N., Nordlander P., Ajayan P. M., Lou J., Fang Z. Y. Plasmonic hot electron induced structural phase transition in a MoS2 monolayer [J]. Advanced Materials, 2014, 26(37): 6467-6471.
[120] Wang Z., Zhang T. Y., Ding M., Dong B. J., Li Y. X., Chen M. L., Li X. X., Huang J. Q., Wang H. W., Zhao X. H., Li Y., Li D., Jia C. K., Sun L. D., Guo H. H., Ye Y., Sun D. M., Chen Y. S., Yang T., Zhang J., Ono S. P., Han Z., Zhang Z. D. Electric-field control of magnetism in a few-layered van der Waals ferromagnetic semiconductor [J]. Nature Nanotechnology, 2018, 13(7): 554-559.
[121] Li X. X., Wu X. J., Li Z. Y., Yang J. L., Hou J. G. Bipolar magnetic semiconductors: a new class of spintronics materials [J]. Nanoscale, 2012, 4(18): 5680-5685.
[122] Dhoot A. S., Israel C., Moya X., Mathur N. D., Friend R. H. Large electric field effect in electrolyte-gated manganites [J]. Physical Review Letters, 2009, 102(13): 136402.
[123] Huang J. S., Li P., Ren X. X., Guo Z. X. Promising properties of a sub-5-nm monolayer MoSi2N4 transistor [J]. Physical Review Applied, 2021, 16(4): 044022.
[124] Davies F. H., Price C. J., Taylor N. T., Davies S. G., Hepplestone S. P. Band alignment of transition metal dichalcogenide heterostructures [J]. Physical Review B, 2021, 103(4): 045417.
[125] Ubrig N., Ponomarev E., Zultak J., Domaretskiy D., Zólyomi V., Terry D., Howarth J., Ignacio G. L., Zhukov A., Kudrynskyi Z. R., Kovalyuk Z. D., Patané A., Taniguchi T., Watanabe K., Gorbachev R. V., Fal’ko V. I., Morpurgo A. F. Design of van der Waals interfaces for broad-spectrum optoelectronics [J]. Nature Materials, 2020, 19(3): 299-304.
[126] Özçelik V. O., Azadani J. G., Yang C., Koester S. J., Low T. Band alignment of two-dimensional semiconductors for designing heterostructures with momentum space matching [J]. Physical Review B, 2016, 94(3): 035125.
[127] Bora M., Deb P. Magnetic proximity effect in two-dimensional van der Waals heterostructure [J]. Journal of Physics: Materials, 2021, 4(3): 034014.
[128] Zhu R., Zhang W., Shen W., Wong P. K. J., Wang Q. X., Liang Q. J., Tian Z., Zhai Y., Qiu C. W., Wee A. T. S. Exchange bias in van der Waals CrCl3/Fe3GeTe2 heterostructures [J]. Nano Letters, 2020, 20(7): 5030-5035.
[129] Pan J. B., Yu J. B., Zhang Y. F., Du S. X., Janotti A., Liu C. X., Yan Q. M. Quantum anomalous Hall effect in two-dimensional magnetic insulator heterojunctions [J]. npj Computational Materials, 2020, 6(1): 152.
[130] Akanda M. R. K., Lake R. K. Magnetic properties of NbSi2N4, VSi2N4, and VSi2P4 monolayers [J]. Applied Physics Letters, 2021, 119(5): 052402.
[131] Khan M. A., Erementchouk M., Hendrickson J., Leuenberger M. N. Electronic and optical properties of vacancy defects in single-layer transition metal dichalcogenides [J]. Physical Review B, 2017, 95(24): 245435.
[132] Kaasbjerg K., Low T., Jauho A. P. Electron and hole transport in disordered monolayer MoS2: Atomic vacancy induced short-range and Coulomb disorder scattering [J]. Physical Review B, 2019, 100(11): 115409.
[133] Shin D. H., Wang G., Han M. J., Lin Z. Y., O'hara A., Chen F. Y., Lin J. H., Pantelides S. T. Preferential hole defect formation in monolayer WSe2 by electron-beam irradiation [J]. Physical Review Materials, 2021, 5(4): 044002.
[134] Zhang Z. P., Gong Y., Zou X. L., Liu P., Yang P. F., Shi J. P., Zhao L. Y., Zhang Q., Gu L., Zhang Y. F. Epitaxial growth of two-dimensional metal–semiconductor transition-metal dichalcogenide vertical stacks (VSe2/MX2) and their band alignments [J]. ACS Nano, 2019, 13(1): 885-893.
[135] Wang B. L., Luo H., Wang X. W., Wang E. , Sun Y. F., Tsai Y. C., Zhu H., Liu P., Jiang K. L., Liu K. Bifunctional NbS2-based ssymmetric heterostructure for lateral and vertical electronic devices [J]. ACS Nano, 2020, 14(1): 175-184.
[136] Fu Q. D., Wang X. W., Zhou J. D., Xia J., Zeng Q., Lv D. H., Zhu C., Wang X. L., Shen Y., Li X. M., Hua Y. N., Liu F. C., Shen Z. X., Jin C. H., Liu Z. One-step synthesis of metal/semiconductor heterostructure NbS2/MoS2 [J]. Chemistry of Materials, 2018, 30(12): 4001-4007.
[137] Wang Y., Kim J. C., Wu R. J., Martinez J., Song X. J., Yang J., Zhao F., Mkhoyan A., Jeong H. Y., Chhowalla M. Van der Waals contacts between three-dimensional metals and two-dimensional semiconductors [J]. Nature, 2019, 568(7750): 70-74.
[138] Zhang Y. B., Tan Y. W., Stormer H. L., Kim P. Experimental observation of the quantum Hall effect and Berry's phase in graphene [J]. Nature, 2005, 438(7065): 201-204.
[139] Berger C., Song Z. , Li X. B., Wu X. S., Brown N., Naud C., Mayou D., Li Ti., Hass J., Marchenkov Al. N., Conrad E. H., First P. N., De Heer W. A. Electronic confinement and coherence in patterned epitaxial graphene [J]. Science, 2006, 312(5777): 1191-1196.
[140] Son Y. W., Cohen M. L., L. Steven G. Erratum: Half-metallic graphene nanoribbons [J]. Nature, 2007, 446(7133): 342-342.
[141] Chhowalla M., Shin H. S., Eda G., Li L. J., Loh K. P., Zhang H. The chemistry of two-dimensional layered transition metal dichalcogenide nanosheets [J]. Nature Chemistry, 2013, 5(4): 263-275.
[142] Zhang Y., Zhang Y. F., Ji Q. Q., Ju J., Yuan H. T., Shi J. P., Gao T., Ma D. L., Liu M. X., Chen Y. B., Song X. J., Hwang H. Y., Cui Y., Liu Z. F. Controlled growth of high-quality monolayer WS2 Layers on sapphire and imaging its grain boundary [J]. ACS Nano, 2013, 7(10): 8963-8971.
[143] Tongay S., Fan W., Kang J., Park J. G., Koldemir U., Suh J., Narang D. S., Liu K., Ji J., Li J. B., Sinclair R., Wu J. Q. Tuning interlayer coupling in large-area heterostructures with CVD-grown MoS2 and WS2 monolayers [J]. Nano Letters, 2014, 14(6): 3185-3190.
[144] Shin G. H.Yuk, Park C. , Lee K. J., Jin H. J., Choi S. Y. Ultrasensitive phototransistor based on WSe2-MoS2 van der Waals heterojunction [J]. Nano Letters, 2020, 20(8): 5741-5748.
[145] Xiao D., Liu G. B., Feng W., Xu X., Yao W. Coupled spin and valley physics in monolayers of MoS2 and other group-VI dichalcogenides [J]. Physical Review Letters, 2012, 108(19): 196802.
[146] Azizi A., Dogan M., Long H., Cain J. D., Lee K. J., Eskandari R., Varieschi A., Glazer E. C., Cohen M. L., Zettl A. High-performance atomically-thin room-temperature NO2 sensor [J]. Nano Letters, 2020, 20(8): 6120-6127.
[147] Rani R., Yoshimura A., Das S., Sahoo M. R., Kundu A., Sahu K. K., Meunier V., Nayak S. K., Koratkar N., Hazra K. S. Sculpting artificial edges in monolayer MoS2 for controlled formation of surface-enhanced raman hotspots [J]. ACS Nano, 2020, 14(5): 6258-6268.
[148] Krishnamurthi S., Brocks G. Spin/charge density waves at the boundaries of transition metal dichalcogenides [J]. Physical Review B, 2020, 102(16): 161106(R).
[149] Zhang T. Y., Liu M. Z., Fujisawa K., Lucking M., Beach K., Zhang F., Shanmugasundaram M., Krayev A., Murray W., Lei Y., Yu Z. H., Sanchez D., Liu Z. W., Terrones H. , Elías A., Terrones M. Spatial control of substitutional dopants in hexagonal monolayer WS2: The effect of edge termination [J]. Small, 2023, 10(6): 2205800.
[150] Chowdhury T., Sadler E. C., Kempa T. J. Progress and prospects in transition-metal dichalcogenide research beyond 2D [J]. Chemical Reviews, 2020, 120(22): 12563-12591.
[151] Pulkin A., Yazyev O. V. Controlling the quantum spin hall edge states in two-dimensional transition metal dichalcogenides [J]. The Journal of Physical Chemistry Letters, 2020, 11(17): 6964-6969.
[152] Xu R. Z., Liu B. L., Zou X. L., Cheng H. M. Half-metallicity in Co-doped WSe2 nanoribbons [J]. ACS Applied Materials & Interfaces, 2017, 9(44): 38796-38801.
[153] Kresse G., Hafner J. Ab initio molecular dynamics for liquid metals [J]. Physical Review B: Condens Matter, 1993, 47(1): 558-561.
[154] Chen Q., Li H., Xu W. S., Wang S. S., Sawada H., Allen C. S., Kirkland A. I., Grossman J. C., Warner J. H. Atomically flat zigzag edges in monolayer MoS2 by thermal annealing [J]. Nano Letters, 2017, 17(9): 5502-5507.
[155] Rasmussen S. C. The 18-electron rule and electron counting in transition metal compounds: Theory and application [J]. ChemTexts, 2015, 1(1): 10.
[156] Pashley M. D. Electron counting model and its application to island structures on molecular-beam epitaxy grown GaAs(001) and ZnSe(001) [J]. Physical Review B, 1989, 40(15): 10481-10487.
[157] Lee W. J., Kim Y. S. Dimer-vacancy reconstructions of the GaN and ZnO(10-11) surfaces: Density functional theory calculations [J]. Physical Review B, 2011, 84(11): 115318.
[158] Deng H. X., Li S. S., Li J. B., Wei S. H. Effect of hydrogen passivation on the electronic structure of ionic semiconductor nanostructures [J]. Physical Review B, 2012, 85(19): 195328.
[159] Wang Q., Shao Y., Shi X. Mechanism of charge redistribution at the metal-semiconductor and semiconductor-semiconductor interfaces of metal-bilayer MoS2 junctions [J]. Journal of Chemical Physics, 2020, 152(24): 244701.
[160] Guan X. X., Zhu G. J., Wei X. L., Cao J. X. Tuning the electronic properties of monolayer MoS2, MoSe2 and MoSSe by applying z-axial strain [J]. Chemical Physics Letters, 2019, 730(11): 191-197.
[161] Ataca C., Şahin H., Aktürk E., Ciraci S. Mechanical and electronic properties of MoS2 nanoribbons and their defects [J]. The Journal of Physical Chemistry C, 2011, 115(10): 3934-3941.
[162] Chen R. S., Ding G. L., Zhou Y., Han S. T. Fermi-level depinning of 2D transition metal dichalcogenide transistors [J]. Journal of Materials Chemistry C, 2021, 9(35): 11407-11427.
[163] Wu R. J., Udyavara S., Ma R., Wang Y., Chhowalla M., Birol T., Koester S. J., Neurock M., Mkhoyan K. A. Visualizing the metal-MoS2 contacts in two-dimensional field-effect transistors with atomic resolution [J]. Physical Review Materials, 2019, 3(11): 111001.
[164] Shao Y. F., Wang Q., Pan H., Shi X. Q. Van der Waals contact to 2D semiconductors with a switchable electric dipole: Achieving both n- and p-type Ohmic contacts to metals with a wide range of work functions [J]. Advanced Electronic Materials, 2020, 6(3): 1900981.
[165] Yu L. L., Zubair A., Santos E. J. G., Zhang X., Lin Y. X., Zhang Y. H., Palacios T. High-performance WSe2 complementary metal oxide semiconductor technology and integrated circuits [J]. Nano Letters, 2015, 15(8): 4928-4934.
[166] Zhang X. K., Liu B. S., Gao L., Yu H. H., Liu X. Z., Du J. L., Xiao J. K., Liu Y. H., Gu L., Liao Q. J., Kang Z., Zhang Z., Zhang Y. Near-ideal van der Waals rectifiers based on all-two-dimensional Schottky junctions [J]. Nature Communications, 2021, 12(1): 1522.
[167] Li H., Cheng M., Wang P., Du R. F., Song L. Y., He J., Shi J. P. Reducing contact resistance and boosting device performance of monolayer MoS2 by in situ Fe doping [J]. Advanced Materials, 2022, 34(18): 2200885.
[168] Singh A., Singh A. K. Origin of n-type conductivity of monolayer MoS2 [J]. Physical Review B, 2019, 99(12): 121201.
[169] Liu Y., Guo J., Zhu E. B., Liao L., Lee S. J., Ding M. N., Shakir I., Gambin V., Huang Y., Duan X. F. Approaching the Schottky–Mott limit in van der Waals metal–semiconductor junctions [J]. Nature, 2018, 557(7707): 696-700.
[170] Xia H., Luo M., Wang W. J., Wang H. L., Li T. X., Wang Z., Xu H. Y., Chen Y., Zhou Y., Wang F., Xie R. Z., Wang P., Hu W. D., Lu W. Pristine PN junction toward atomic layer devices [J]. Light: Science & Applications, 2022, 11(1): 170.
[171] Pak S., Jang S., Kim T. H., Lim J., Hwang J., Cho Y., Chang H., Jang A. R., Park K., Hong J., Cha S. N. Electrode-induced self-healed monolayer MoS2 for high performance transistors and phototransistors [J]. Advanced Materials, 2021, 33(41): 2102091.
[172] Gaspari R., Manna L., Cavalli A. A theoretical investigation of the (0001) covellite surfaces [J]. The Journal of Chemical Physics, 2014, 141(4): 044702.
[173] H. Fjellvag, F. Gronvold, S. Stolen, A. F. Andresen, R. Muellerkaefu, Simon A. Low-temperature structural distortion in CuS [J]. Zeitschrift für Kristallographie, 1988, 184(1-2): 111-121.
[174] Mazin I. I. Structural and electronic properties of the two-dimensional superconductor CuS with 4/3-valent copper [J]. Physical Review B, 2012, 85(11): 115133.
[175] Gainov R. R., Dooglav A. V., Pen’kov I. N., Mukhamedshin I. R., Mozgova N. N., Evlampiev I. A., Bryzgalov I. A. Phase transition and anomalous electronic behavior in the layered superconductor CuS probed by NQR [J]. Physical Review B, 2009, 79(7): 075115.
[176] Liang W., Whangbo M. H. Conductivity anisotropy and structural phase transition in covellite CuS [J]. Solid State Communications, 1993, 85(5): 405-408.
[177] Morales A., Dos E. C., De H. A., Duarte H. A. First-principles calculations and electron density topological analysis of covellite (CuS) [J]. The Journal of Physical Chemistry A, 2014, 118(31): 5823-5831.
[178] Zollner K., Junior P. E., Fabian J. Strain-tunable orbital, spin-orbit, and optical properties of monolayer transition-metal dichalcogenides [J]. Physical Review B, 2019, 100(19): 195126.
[179] Chen Y. T., Gong P. L., Ren Y. T., Hu L., Zhang H., Wang J. L., Huang L., Shi X. Q. Interlayer quasi-bonding interactions in 2D layered materials: A classification according to the occupancy of involved energy bands [J]. Journal of Physical Chemistry Letters, 2021, 12(50): 11998-12004.
[180] Zhao Y. D., Qiao J. S., Yu P., Hu Z. X., Lin Z. Y., Lau S. P., Liu Z., Ji W., Chai Y. Extraordinarily strong interlayer interaction in 2D layered PtS2 [J]. Advanced Materials, 2016, 28(12): 2399-2407.
[181] Padilha J. E., Peelaers H., Janotti A., Van De Walle C. G. Nature and evolution of the band-edge states in MoS2: From monolayer to bulk [J]. Physical Review B, 2014, 90(20): 205420.
[182] Farmanbar M., Brocks G. First-principles study of van der Waals interactions and lattice mismatch at lattice mismatch MoS2/metal interfaces [J]. Physical Review B, 2016, 93(8): 085304.