Local Mapping Of The Thickness-Dependent Dielectric Constant Of Mos2

The dielectric constant (epsilon) 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 epsilon of MoS2 nanoflakes using a nondestructive electrostatic force microscopy (EFM) imaging technique. EFM is used to simultaneously probe the thickness and local epsilon 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 epsilon increases with the thickness and saturates to the bulk value, consistent with previous theoretical and experimental results of dielectric constants for MoS2 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.