title: Impurities and Electronic Property Variations of Natural MoS2 Crystal Surfaces.
abstract: 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.
authors: Department of Materials Science and Engineering, The University of Texas at Dallas , 800 Campbell Road, Richardson, Texas 75080, Unites States.
authors: Rafik
authors: R
authors: Addou
authors: Department of Materials Science and Engineering, The University of Texas at Dallas , 800 Campbell Road, Richardson, Texas 75080, Unites States.
authors: Stephen
authors: S
authors: McDonnell
authors: Department of Materials Science and Engineering, The University of Texas at Dallas , 800 Campbell Road, Richardson, Texas 75080, Unites States.|Centro de Investigación en Materiales Avanzados, S.C. (CIMAV), Unidad Monterrey, Alianza Norte 202, 66600 Apodaca, Nuevo León México.
authors: Diego
authors: D
authors: Barrera
authors: Zaibing
authors: Z
authors: Guo
authors: Department of Materials Science and Engineering, The University of Texas at Dallas , 800 Campbell Road, Richardson, Texas 75080, Unites States.
authors: Angelica
authors: A
authors: Azcatl
authors: Department of Materials Science and Engineering, The University of Texas at Dallas , 800 Campbell Road, Richardson, Texas 75080, Unites States.
authors: Jian
authors: J
authors: Wang
authors: Department of Materials Science and Engineering, The University of Texas at Dallas , 800 Campbell Road, Richardson, Texas 75080, Unites States.
authors: Hui
authors: H
authors: Zhu
authors: Department of Materials Science and Engineering, The University of Texas at Dallas , 800 Campbell Road, Richardson, Texas 75080, Unites States.
authors: Christopher L
authors: CL
authors: Hinkle
authors: Department of Materials Science and Engineering, The University of Texas at Dallas , 800 Campbell Road, Richardson, Texas 75080, Unites States.
authors: Manuel
authors: M
authors: Quevedo-Lopez
authors: Husam N
authors: HN
authors: Alshareef
authors: Texas Instruments Incorporated, 13121 TI Boulevard, MS-365, Dallas, Texas 75243, Unites States.
authors: Luigi
authors: L
authors: Colombo
authors: Department of Materials Science and Engineering, The University of Texas at Dallas , 800 Campbell Road, Richardson, Texas 75080, Unites States.
authors: Julia W P
authors: JW
authors: Hsu
authors: Department of Materials Science and Engineering, The University of Texas at Dallas , 800 Campbell Road, Richardson, Texas 75080, Unites States.
authors: Robert M
authors: RM
authors: Wallace
keywords: Fermi level shift; MoS2; X-ray photoelectron spectroscopy; electron affinity; impurities; scanning tunneling microscopy; surface defects; work function