Facile synthesis of MoS2 and MoxW1-xS2 triangular monolayers

Single- and few-layered transition metal dichalcogenides, such as MoS2 and WS2, are emerging two-dimensional materials exhibiting numerous and unusual physico-chemical properties that could be advantageous in the fabrication of unprecedented optoelectronic devices. Here we report a novel and alternative route to synthesize triangular monocrystals of MoS2 and MoxW1-xS2 by annealing MoS2 and MoS2/WO3 precursors, respectively, in the presence of sulfur vapor. In particular, the MoxW1-xS2 triangular monolayers show gradual concentration profiles of W and Mo whereby Mo concentrates in the islands’ center and W is more abundant on the outskirts of the triangular monocrystals. These observations were confirmed by atomic force microscopy, and high-resolution transmission electron microscopy, as well as Raman and photoluminescence spectroscopy. The presence of tunable PL signals depending on the MoxW1-xS2 stoichiometries in 2D monocrystals opens up a wide range of applications in electronics and optoelectronics.

[1]  Hua Zhang,et al.  The chemistry of two-dimensional layered transition metal dichalcogenide nanosheets. , 2013, Nature chemistry.

[2]  P. Ajayan,et al.  Large Area Vapor Phase Growth and Characterization of MoS2 Atomic Layers on SiO2 Substrate , 2011, 1111.5072.

[3]  Andre K. Geim,et al.  Two-dimensional atomic crystals. , 2005, Proceedings of the National Academy of Sciences of the United States of America.

[4]  E. Johnston-Halperin,et al.  Progress, challenges, and opportunities in two-dimensional materials beyond graphene. , 2013, ACS nano.

[5]  Rajeev Kumar,et al.  Transport properties of monolayer MoS2 grown by chemical vapor deposition. , 2014, Nano letters.

[6]  T. Wieting,et al.  Infrared and Raman Studies of Long-Wavelength Optical Phonons in Hexagonal Mo S 2 , 1971 .

[7]  Zhiwen Liu,et al.  Extraordinary Second Harmonic Generation in Tungsten Disulfide Monolayers , 2014, Scientific Reports.

[8]  Jun Lou,et al.  CVD-grown monolayered MoS2 as an effective photosensor operating at low-voltage , 2014 .

[9]  R. Tenne,et al.  High-Rate, Gas-Phase Growth of MoS2 Nested Inorganic Fullerenes and Nanotubes , 1995, Science.

[10]  Jun Lou,et al.  Vapour phase growth and grain boundary structure of molybdenum disulphide atomic layers. , 2013, Nature materials.

[11]  A. Splendiani,et al.  Emerging photoluminescence in monolayer MoS2. , 2010, Nano letters.

[12]  Andras Kis,et al.  Ultrasensitive photodetectors based on monolayer MoS2. , 2013, Nature nanotechnology.

[13]  Xiaodong Xu,et al.  Vapor-solid growth of high optical quality MoS₂ monolayers with near-unity valley polarization. , 2013, ACS nano.

[14]  Ruitao Lv,et al.  Controlled synthesis and transfer of large-area WS2 sheets: from single layer to few layers. , 2013, ACS nano.

[15]  M. Terrones,et al.  Photosensor Device Based on Few‐Layered WS2 Films , 2013 .

[16]  M. Terrones,et al.  Ultrashort optical pulse characterization using WS₂ monolayers. , 2014, Optics letters.

[17]  Wang Yao,et al.  Spin and pseudospins in layered transition metal dichalcogenides , 2014, Nature Physics.

[18]  Zhiyuan Zeng,et al.  Metal dichalcogenide nanosheets: preparation, properties and applications. , 2013, Chemical Society reviews.

[19]  A. Radenović,et al.  Single-layer MoS2 transistors. , 2011, Nature nanotechnology.

[20]  Hongzheng Chen,et al.  Graphene-like two-dimensional materials. , 2013, Chemical reviews.

[21]  Yilei Li,et al.  Probing symmetry properties of few-layer MoS2 and h-BN by optical second-harmonic generation. , 2013, Nano letters.

[22]  Daniel Wolverson,et al.  Raman-scattering measurements and first-principles calculations of strain-induced phonon shifts in monolayer MoS2 , 2013 .

[23]  P. Ajayan,et al.  Nanomechanical cleavage of molybdenum disulphide atomic layers , 2014, Nature Communications.

[24]  Mauricio Terrones,et al.  Novel hetero-layered materials with tunable direct band gaps by sandwiching different metal disulfides and diselenides , 2013, Scientific Reports.

[25]  P. Ajayan,et al.  Band gap engineering and layer-by-layer mapping of selenium-doped molybdenum disulfide. , 2014, Nano letters.

[26]  SUPARNA DUTTASINHA,et al.  Van der Waals heterostructures , 2013, Nature.

[27]  Qing Hua Wang,et al.  Electronics and optoelectronics of two-dimensional transition metal dichalcogenides. , 2012, Nature nanotechnology.

[28]  M. Terrones,et al.  Electronic and vibrational properties of defective transition metal dichalcogenide Haeckelites: new 2D semi-metallic systems , 2014 .

[29]  Liying Jiao,et al.  Controlled synthesis of highly crystalline MoS2 flakes by chemical vapor deposition. , 2013, Journal of the American Chemical Society.

[30]  J. Shan,et al.  Atomically thin MoS₂: a new direct-gap semiconductor. , 2010, Physical review letters.

[31]  D. Smirnov,et al.  New First Order Raman-active Modes in Few Layered Transition Metal Dichalcogenides , 2014, Scientific Reports.

[32]  J. Coleman,et al.  Two-Dimensional Nanosheets Produced by Liquid Exfoliation of Layered Materials , 2011, Science.

[33]  K. Novoselov,et al.  Strong Light-Matter Interactions in Heterostructures of Atomically Thin Films , 2013, Science.

[34]  P. Ajayan,et al.  Second harmonic microscopy of monolayer MoS 2 , 2013, 1302.3935.

[35]  Yiming Zhu,et al.  Growth of Large‐Area 2D MoS2(1‐x)Se2x Semiconductor Alloys , 2014, Advanced materials.

[36]  Jing Kong,et al.  van der Waals epitaxy of MoS₂ layers using graphene as growth templates. , 2012, Nano letters.

[37]  Lain‐Jong Li,et al.  Large-area synthesis of highly crystalline WSe(2) monolayers and device applications. , 2014, ACS nano.

[38]  Lain‐Jong Li,et al.  Synthesis of Large‐Area MoS2 Atomic Layers with Chemical Vapor Deposition , 2012, Advanced materials.

[39]  Jing Kong,et al.  Electronic transport and device prospects of monolayer molybdenum disulphide grown by chemical vapour deposition. , 2014, Nature communications.

[40]  Dong Wang,et al.  Tunable band gap photoluminescence from atomically thin transition-metal dichalcogenide alloys. , 2013, ACS nano.

[41]  Timothy C. Berkelbach,et al.  Grains and grain boundaries in highly crystalline monolayer molybdenum disulphide. , 2013, Nature Materials.

[42]  Yi Liu,et al.  Controlled Scalable Synthesis of Uniform, High-Quality Monolayer and Few-layer MoS2 Films , 2013, Scientific Reports.

[43]  J. Myoung,et al.  Layer-controlled, wafer-scale, and conformal synthesis of tungsten disulfide nanosheets using atomic layer deposition. , 2013, ACS nano.

[44]  Ruitao Lv,et al.  Extraordinary room-temperature photoluminescence in triangular WS2 monolayers. , 2012, Nano letters.