Thickness-Dependent Dielectric Screening in Few-Layer Phosphorus.

The dielectric screening plays a critical role in determining the fundamental electronic properties in semiconductor devices. In this work, we report a noncontact and spatially resolved method, based on Kelvin probe force microscopy (KPFM), to obtain the inherent dielectric screening of black phosphorus (BP) and violet phosphorus (VP) as a function of the thickness. Interestingly, the dielectric constant of VP and BP flakes increases monotonically and then saturates to the bulk value, which is consistent with our first-principles calculations. The dielectric screening in VP has a much weaker dependence on the number of layers. This could be ascribed to a strong electron orbital overlap between two adjacent layers of VP, resulting in a strong interlayer coupling. The findings of our work are significant both for fundamental studies of dielectric screening and for more technical applications in nanoelectronic devices based on layered 2D materials.