Local Mapping of the Thickness-Dependent Dielectric Constant of MoS2

The dielectric constant (ε) is a key parameter to consider when determining the fundamental electrical properties of the charging and screening of charges in optoelectronic devices based on two-dimensional (2D) layered materials with van der Waals interactions. In this study, we report a direct local mapping of the thickness-dependent ε of MoS 2 nanoflakes using a nondestructive electrostatic force microscopy (EFM) imaging technique. EFM is used to simultaneously probe the thickness and local ε value of regions with different thicknesses by detecting a cantilever deflection while applying DC bias voltage between the conducting tip and the substrate. The measured ε increases with the thickness and saturates to the bulk value, consistent with previous theoretical and experimental results of dielectric constants for MoS 2 at different thicknesses. Our works provide quantitative information pertaining to the thickness-dependent electric permittivity, which can be useful in quantitative design of high-performance and multifunctional nanoelectronic devices based on layered 2D materials.