We investigated the surface potential (Vsurf) of exfoliated MoS2 flakes on bare and Au-coated SiO2/Si substrates using Kelvin probe force microscopy. The Vsurf of MoS2 single layers was larger on the Au-coated substrates than on the bare substrates; our theoretical calculations indicate that this may be caused by the formation of a larger electric dipole at the MoS2/Au interface leading to a modified band alignment. Vsurf decreased as the thickness of the flakes increased until reaching the bulk value at a thickness of a20 nm (a30 layers) on the bare and a80 nm (a120 layers) on the Au-coated substrates, respectively. This thickness dependence of Vsurf was attributed to electrostatic screening in the MoS2 layers. Thus, a difference in the thickness at which the bulk Vsurf appeared suggests that the underlying substrate has an effect on the electric-field screening length of the MoS2 flakes. This work provides important insights to help understand and control the electrical properties of metal/MoS2 contacts.
Bibliographical noteFunding Information:
This work was supported by Priority Research Center Program (2010-0020207), International Collaboration Program (NRF-2016K2A9A1A03905001), and Basic Science Research Program (NRF-2016R1D1A1B01009032, NRF-2016R1D1A1A09917491, and NRF-2017R1A2B2010123) through the National Research Foundation of Korea (NRF).
© 2017 American Chemical Society.