Uniform doping of graphene close to the charge neutrality point by polymer-assisted spontaneous assembly of molecular dopants

Hans He, Kyung Ho Kim, Andrey Danilov, Domenico Montemurro, Liyang Yu, Yung Woo Park, Floriana Lombardi, Thilo Bauch, Kasper Moth-Poulsen, Tihomir Iakimov, Rositsa Yakimova, Per Malmberg, Christian Müller, Sergey Kubatkin, Samuel Lara-Avila

Published 2018-05-15Version 1

Tuning the charge carrier density of two-dimensional (2D) materials by incorporating dopants into the crystal lattice is a challenging task. An attractive alternative is the surface transfer doping by adsorption of molecules on 2D crystals, which can lead to ordered molecular arrays. However, such systems, demonstrated in ultra-high vacuum conditions (UHV), are often unstable in ambient conditions. Here we show that air-stable doping of epitaxial graphene on SiC - achieved by spin-coating deposition of 2,3,5,6-tetrafluoro-tetracyano-quino-dimethane (F4TCNQ) incorporated in poly (methyl-methacrylate) - proceeds via the spontaneous accumulation of dopants at the graphene-polymer interface and by the formation of a charge-transfer complex that yields low-disorder, charge-neutral graphene with carrier mobilities ~70,000 cm2/Vs at cryogenic temperatures. The assembly of dopants on 2D materials assisted by a polymer matrix, demonstrated by spin coating wafer-scale substrates in ambient conditions, opens up a scalable technological route towards expanding the functionality of 2D materials.