First-principles Raman spectra of MoS2, WS2 and their heterostructures.

Raman spectra of MoS2, WS2, and their heterostructures are studied by density functional theory. We quantitatively reproduce existing experimental data and present evidence that the apparent discrepancy between intensity ratios observed experimentally can be explained by the high sensitivity of the Raman-active modes to laser polarization. Furthermore, MoS2/WS2 heterostructures up to four layers are considered in every possible combination and stacking order. Each heterostructure configuration possesses a unique Raman spectrum in both frequency and intensity that can be explained by changes in dielectric screening and interlayer interaction. The results establish a set of guidelines for the practical experimental identification of heterostructure configurations.

[1]  C. Kloc,et al.  Effects of lower symmetry and dimensionality on Raman spectra in two-dimensional WSe2 , 2013 .

[2]  P. Ajayan,et al.  Temperature-dependent phonon shifts in monolayer MoS2 , 2013, 1307.2447.

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

[4]  Hugen Yan,et al.  Anomalous lattice vibrations of single- and few-layer MoS2. , 2010, ACS nano.

[5]  G. Kresse,et al.  From ultrasoft pseudopotentials to the projector augmented-wave method , 1999 .

[6]  Soon Cheol Hong,et al.  Thickness and strain effects on electronic structures of transition metal dichalcogenides: 2H- M X 2 semiconductors ( M = Mo, W; X = S, Se, Te) , 2012 .

[7]  Quantitative Raman spectrum and reliable thickness identification for atomic layers on insulating substrates. , 2012, ACS nano.

[8]  Yoshiyuki Kawazoe,et al.  First-Principles Determination of the Soft Mode in Cubic ZrO 2 , 1997 .

[9]  E. Aktürk,et al.  A Comparative Study of Lattice Dynamics of Three- and Two-Dimensional MoS2 , 2011 .

[10]  V. Meunier,et al.  Electronic and thermoelectric properties of assembled graphene nanoribbons with elastic strain and structural dislocation , 2013 .

[11]  Andre K. Geim,et al.  Electric Field Effect in Atomically Thin Carbon Films , 2004, Science.

[12]  D. Basko,et al.  Raman spectroscopy as a versatile tool for studying the properties of graphene. , 2013, Nature nanotechnology.

[13]  M. Dresselhaus,et al.  Synthesis and transfer of single-layer transition metal disulfides on diverse surfaces. , 2013, Nano letters.

[14]  H. Monkhorst,et al.  SPECIAL POINTS FOR BRILLOUIN-ZONE INTEGRATIONS , 1976 .

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

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

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

[18]  Christian Kloc,et al.  Lattice dynamics in mono- and few-layer sheets of WS2 and WSe2. , 2013, Nanoscale.

[19]  Alfredo Pasquarello,et al.  Raman scattering intensities in α-quartz: A first-principles investigation , 2001 .

[20]  Lin-wang Wang,et al.  Electronic structural Moiré pattern effects on MoS2/MoSe2 2D heterostructures. , 2013, Nano letters.

[21]  Georg Kresse,et al.  Ab initio calculation of the lattice dynamics and phase diagram of boron nitride , 1999 .

[22]  Jiaguo Yu,et al.  Preparation and photocatalytic behavior of MoS2 and WS2 nanocluster sensitized TiO2. , 2004, Langmuir : the ACS journal of surfaces and colloids.

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

[24]  Jean-Christophe Charlier,et al.  Identification of individual and few layers of WS2 using Raman Spectroscopy , 2013, Scientific Reports.

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

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

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

[28]  L. Wirtz,et al.  Phonons in single-layer and few-layer MoS2 , 2011 .

[29]  Jeroen van den Brink,et al.  Substrate-induced band gap in graphene on hexagonal boron nitride: Ab initio density functional calculations , 2007 .

[30]  G. Kresse,et al.  Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set , 1996 .

[31]  Georg Kresse,et al.  Ab initio Force Constant Approach to Phonon Dispersion Relations of Diamond and Graphite , 1995 .

[32]  Dominique Baillargeat,et al.  From Bulk to Monolayer MoS2: Evolution of Raman Scattering , 2012 .

[33]  Fabio Pietrucci,et al.  Ab initio study of the vibrational properties of crystalline TeO2: The alpha, beta, and gamma phases , 2006, 0803.4056.

[34]  Anomalous frequency trends in MoS 2 thin films attributed to surface effects , 2013, 1308.6393.

[35]  Wang Yao,et al.  Optical signature of symmetry variations and spin-valley coupling in atomically thin tungsten dichalcogenides , 2012, Scientific Reports.

[36]  Vincent Meunier,et al.  Enhanced thermoelectric figure of merit in assembled graphene nanoribbons , 2012 .