Impurities and Electronic Property Variations of Natural MoS2 Crystal Surfaces.

Room temperature X-ray photoelectron spectroscopy (XPS), inductively coupled plasma mass spectrometry (ICPMS), high resolution Rutherford backscattering spectrometry (HR-RBS), Kelvin probe method, and scanning tunneling microscopy (STM) are employed to study the properties of a freshly exfoliated surface of geological MoS2 crystals. Our findings reveal that the semiconductor 2H-MoS2 exhibits both n- and p-type behavior, and the work function as measured by the Kelvin probe is found to vary from 4.4 to 5.3 eV. The presence of impurities in parts-per-million (ppm) and a surface defect density of up to 8% of the total area could explain the variation of the Fermi level position. High resolution RBS data also show a large variation in the MoSx composition (1.8 < x < 2.05) at the surface. Thus, the variation in the conductivity, the work function, and stoichiometry across small areas of MoS2 will have to be controlled during crystal growth in order to provide high quality uniform materials for future device fabrication.

[1]  Scott Anderson,et al.  Monitoring wafer cleanliness and metal contamination via VPD ICP-MS: Case studies for next generation requirements , 2010 .

[2]  W. Spicer,et al.  Photoemission studies of layered transition metal dichalcogenides , 1977 .

[3]  S. Sanvito,et al.  Possible doping strategies for MoS 2 monolayers: An ab initio study , 2013 .

[4]  M. T. Martínez,et al.  Preparation of a TiO 2 -MoS 2 nanoparticle-based composite by solvothermal method with enhanced photoactivity for the degradation of organic molecules in water under UV light , 2011 .

[5]  D. Beauchemin.  Inductively coupled plasma mass spectrometry. , 2006, Analytical chemistry.

[6]  Yang,et al.  Raman study and lattice dynamics of single molecular layers of MoS2. , 1991, Physical review. B, Condensed matter.

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

[8]  M. Batzill,et al.  Direct observation of interlayer hybridization and Dirac relativistic carriers in graphene/MoS₂ van der Waals heterostructures. , 2015, Nano letters.

[9]  Mietek Jaroniec,et al.  Synergetic effect of MoS2 and graphene as cocatalysts for enhanced photocatalytic H2 production activity of TiO2 nanoparticles. , 2012, Journal of the American Chemical Society.

[10]  R. H. Williams,et al.  Electronic properties of cleaved molybdenum disulphide surfaces , 1974 .

[11]  F. Wypych,et al.  1T‐MoS2, A New Metallic Modification of Molybdenum Disulfide. , 1993 .

[12]  R. Powell.  Interface Barrier Energy Determination from Voltage Dependence of Photoinjected Currents , 1970 .

[13]  Moon J. Kim,et al.  Atomically thin heterostructures based on single-layer tungsten diselenide and graphene. , 2014, Nano letters.

[14]  R. Lieth,et al.  Transition Metal Dichalcogenides , 1977 .

[15]  S. Ciraci,et al.  Dissociation of H 2 O at the vacancies of single-layer MoS 2 , 2012 .

[16]  Kaustav Banerjee,et al.  Functionalization of transition metal dichalcogenides with metallic nanoparticles: implications for doping and gas-sensing. , 2015, Nano letters.

[17]  R. Haasch,et al.  2-D Material Molybdenum Disulfide Analyzed by XPS , 2014 .

[18]  Textured MoS2 thin films obtained on tungsten: Electrical properties of the W/MoS2 contact , 2000 .

[19]  D. Tsai,et al.  Monolayer MoS2 heterojunction solar cells. , 2014, ACS nano.

[20]  John Robertson,et al.  Sulfur vacancies in monolayer MoS2 and its electrical contacts , 2013 .

[21]  M. Kamaratos,et al.  Adsorption studies on Ar+ -sputtered MoS2(0001) , 1986 .

[22]  Joshua J. Golden,et al.  Rhenium variations in molybdenite (MoS2): Evidence for progressive subsurface oxidation , 2013 .

[23]  H. Skriver,et al.  Surface energy and work function of elemental metals. , 1992, Physical review. B, Condensed matter.

[24]  Wolfram Jaegermann,et al.  Band lineup of layered semiconductor heterointerfaces prepared by van der Waals epitaxy: Charge transfer correction term for the electron affinity rule , 1999 .

[25]  Moon J. Kim,et al.  Transition metal dichalcogenide and hexagonal boron nitride heterostructures grown by molecular beam epitaxy , 2015 .

[26]  J. Appenzeller,et al.  High performance multilayer MoS2 transistors with scandium contacts. , 2013, Nano letters.

[27]  R. Wallace,et al.  Surface Defects on Natural MoS2. , 2015, ACS applied materials & interfaces.

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

[29]  Wilford N. Hansen,et al.  Standard reference surfaces for work function measurements in air , 2001 .

[30]  K. Kimura,et al.  Improvement of sensitivity in high-resolution Rutherford backscattering spectroscopy. , 2011, The Review of scientific instruments.

[31]  C. Nordling,et al.  Electron spectroscopic determination of the chemical valence state , 1964 .

[32]  K. Kalantar-zadeh,et al.  Characterization of metal contacts for two-dimensional MoS2 nanoflakes , 2013 .

[33]  M. Batzill,et al.  Wet-transfer of CVD-grown graphene onto sulfur-protected W(110) , 2015 .

[34]  S. Sze,et al.  Physics of Semiconductor Devices: Sze/Physics , 2006 .

[35]  Moon J. Kim,et al.  HfSe2 thin films: 2D transition metal dichalcogenides grown by molecular beam epitaxy. , 2015, ACS nano.

[36]  R. Wallace,et al.  Surface oxidation energetics and kinetics on MoS2 monolayer , 2015 .

[37]  P. Ye,et al.  Channel length scaling of MoS2 MOSFETs. , 2012, ACS nano.

[38]  R. Wallace.  In-Situ Studies on 2D Materials , 2014 .

[39]  K. Banerjee,et al.  Correction to MoS2 Field-Effect Transistor for Next-Generation Label-Free Biosensors , 2014 .

[40]  Stephen McDonnell,et al.  Defect-dominated doping and contact resistance in MoS2. , 2014, ACS nano.

[41]  Phong Nguyen,et al.  Controlled, defect-guided, metal-nanoparticle incorporation onto MoS2 via chemical and microwave routes: electrical, thermal, and structural properties. , 2013, Nano letters.

[42]  H. Tributsch,et al.  The Role of Carrier Diffusion and Indirect Optical Transitions in the Photoelectrochemical Behavior of Layer Type d‐Band Semiconductors , 1980 .

[43]  D. Jena,et al.  Charge Scattering and Mobility in Atomically Thin Semiconductors , 2013, 1310.7157.

[44]  Marco Bernardi,et al.  Extraordinary sunlight absorption and one nanometer thick photovoltaics using two-dimensional monolayer materials. , 2013, Nano letters.

[45]  H. Michaelson.  The work function of the elements and its periodicity , 1977 .

[46]  H. Itoh,et al.  Scanning tunneling microscopy observation of MoS2 surface and gold clusters deposited on MoS2 surface , 1990 .

[47]  Deji Akinwande,et al.  High-performance, highly bendable MoS2 transistors with high-k dielectrics for flexible low-power systems. , 2013, ACS nano.

[48]  N. McIntyre,et al.  Effects of argon ion bombardment on basal plane and polycrystalline MoS2 , 1990 .

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

[50]  K. Ng,et al.  The Physics of Semiconductor Devices , 2019, Springer Proceedings in Physics.

[51]  R. Prins,et al.  Scanning Tunneling Microscopic Investigation of 1T-MoS2 , 1998 .

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

[53]  R. Wallace,et al.  Impact of intrinsic atomic defects on the electronic structure of MoS2 monolayers , 2014, Nanotechnology.

[54]  C. Battaglia,et al.  Hole contacts on transition metal dichalcogenides: interface chemistry and band alignments. , 2014, ACS nano.

[55]  Hisato Yamaguchi,et al.  Photoluminescence from chemically exfoliated MoS2. , 2011, Nano letters.

[56]  J. Wilson,et al.  The transition metal dichalcogenides discussion and interpretation of the observed optical, electrical and structural properties , 1969 .

[57]  P. D. Fleischauer,et al.  Summary Abstract: Noble gas ion bombardment of the basal plane surface of MoS2 , 1987 .

[58]  R. Frindt,et al.  Single Crystals of MoS2 Several Molecular Layers Thick , 1966 .

[59]  Peide D. Ye,et al.  Contact research strategy for emerging molybdenum disulfide and other two-dimensional field-effect transistors , 2014 .

[60]  R. R. Haering,et al.  Structural destabilization induced by lithium intercalation in MoS2 and related compounds , 1983 .

[61]  W. Jaegermann,et al.  Li intercalation across and along the van der Waals surfaces of MoS2(0001) , 1995 .

[62]  P. Ye,et al.  (Invited) Fundamentals in MoS2 Transistors: Dielectric, Scaling and Metal Contacts , 2013 .

[63]  W. 0. Winer.  Molybdenum disulfide as a lubricant: A review of the fundamental knowledge , 1967 .

[64]  M. Batzill,et al.  Interface properties of CVD grown graphene transferred onto MoS2(0001). , 2014, Nanoscale.

[65]  W. Sachtler,et al.  The work function of gold , 1966 .

[66]  Gautam Gupta,et al.  Phase-engineered low-resistance contacts for ultrathin MoS2 transistors. , 2014, Nature materials.

[67]  B. Parkinson,et al.  Detailed photocurrent spectroscopy of the semiconducting group VIB transition metal dichalcogenides , 1982 .