Impurities and Electronic Property Variations of Natural MoS<inf>2</inf> Crystal Surfaces

Rafik Addou, Stephen McDonnell, Diego Barrera, Zaibing Guo, Angelica Azcatl, Jian Wang, Hui Zhu, Christopher L. Hinkle, Manuel Quevedo-Lopez, Husam N. Alshareef, Luigi Colombo, Julia W.P. Hsu, Robert M. Wallace

Research output: Contribution to journalArticlepeer-review


© 2015 American Chemical Society. 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 MoS<inf>2</inf> crystals. Our findings reveal that the semiconductor 2H-MoS<inf>2</inf> 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 MoS<inf>x</inf> composition (1.8 < x < 2.05) at the surface. Thus, the variation in the conductivity, the work function, and stoichiometry across small areas of MoS<inf>2</inf> will have to be controlled during crystal growth in order to provide high quality uniform materials for future device fabrication.
Original languageAmerican English
Pages (from-to)9124-9133
Number of pages10
JournalACS Nano
StatePublished - 22 Sep 2015
Externally publishedYes

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