Engineering the Electronic Structure of Two-Dimensional Materials with Near-Field Electrostatic Effects of Self-Assembled Organic Layers

We compute the electronic structure of two-dimensional (2D) materials decorated with self-assembled organic monolayers using density functional theory. We find that 2D materials are strongly impacted by near-field electrostatic effects resulting from high multipoles of the organic layer electronic density. We show that this effect can lead to significant (~0.5V) modulation of the in-plane potential experienced by electrons in 2D materials within ~4\AA from the molecular layer, with a transition between near- and far-field depending on the lateral extent of the molecules. We develop a theory of this effect, showing that the electrostatic potential of the molecular layer can be approximated by a discretized planar charge density derived from the molecular structure and multipoles. Solving this model computationally and analytically, we propose implementations of this effect to generate novel electronic properties for electrons in 2D materials, such as band gap opening and anisotropic group velocity modulation for monolayer graphene from experimentally achievable molecular assemblies.