CUR - The Council on Undergraduate Research

Electrostatic Doping of 2-Dimensional Material with Organic Molecules

Bukuru Anaclet, Qunfei Zhou, Pierre Darancet Materials Research Science and Engineering Center, Northwestern University 633 Clark St, Evanston, IL 60208

Two-dimensional (2D) materials, such as graphene, hexagonal boron nitride and transition metal
dichalcogenides (TMDs) have shown remarkable electronic and optical properties making them
appealing in a wide range of optical-electronic devices. Most of those applications rely on
properties of the p-n junctions that are achieved by doping. The most widely used doping method
is chemical doping which usually introduces uncontrollable defects. In this work, we propose a
new strategy to dope 2D materials by surface adsorption of organic molecules, which have large
multipole moments that are also tunable by functional groups and orientation. Using first-
principles calculations based on density functional theory, we study the impact of C8-BTBT
molecular layer on electronic properties of graphene and 2D InSe. Our results show that the
organic molecular layer induce a electrostatic potential difference of about 0.8eV in different
regions of the 2D surfaces, which indicates that work function and electron affinity can be
significantly modified, creating in-plane P-N junctions modulable by the assembly of molecules.
Our work demonstrate that surface doping of polar organic molecules provides further
modulation on the functionality of 2D materials for high performance devices.

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