Surface potential and interlayer screening effects of few-layer MoS2 nanoflakes

We report the interlayer screening effects of ultrathin MoS2 nanoflakes with different thicknesses by measuring their surface potential using Kelvin probe microscope. Surface potential of pristine MoS2 nanoflakes decreased with increasing thickness, while after annealing, the trend was opposite and the screening length became smaller. These results were qualitatively explained by a charge transfer model with the built-in electric field induced by trapped charges. The transport mechanism of MoS2 nanoflakes with different thicknesses was also studied by using conductive atomic force microscopy, and the thermonic emission and Fowler-Nordheim tunneling were effective in the forward bias and reverse bias, respectively.