Article: published in Advanced Functional Materials by Pilar Segovia, Cristina Díaz, Fernando Martín, Enrique G. Michel, Félix Zamora, Cristina Gómez-Navarro and Julio Gómez-Herrero, IFIMAC researchers.
Graphene is a wonder material that possesses many outstanding properties, including extraordinary strength, stiffness and high flexibility, which make it a very good candidate to withstand ultrahigh pressure. Nevertheless, the possibility of controlling graphene properties is crucial to promote its use in a variety of applications. In this work, we achieved fine tuning of graphene effective doping by applying ultrahigh pressures (> 10 GPa) using Atomic Force Microscopy (AFM) diamond tips. With this configuration, we irreversibly flattened specific areas against a SiO2 substrate creating p-doped graphene regions with nanometer precision. Importantly, the doping strength depends monotonically on the applied pressure, allowing a precise tuning of the doping level. Density Functional Theory (DFT) calculations point towards chemical bonding of graphene on the underlying substrate as the main/most relevant mechanism for the observed behavior. Through this doping effect, ultrahigh pressure modifications locally improved the contact resistance between graphene and a metal electrode. This is a paramount issue in the field of graphene electronics, since it might allow a remarkable reduction of the power consumption of future graphene-based electronic devices. Our results introduce local application of ultrahigh pressures with AFM as a very powerful tool to tune graphene properties. Thanks to its remarkable mechanical properties, it might also provide a unique platform to carry out chemical reactions of trapped molecules between graphene layers and a substrate at ultrahigh pressures, without the technical drawbacks characteristic of classical high pressure procedures. Moreover, this method can be generalized to other 2D materials, van der Waals heterostructures and related systems. [Full article]
Authors acknowledge financial support from the Spanish Ministry of Economy and Competitiveness, through The “María de Maeztu” Programme for Units of Excellence in R&D (MDM-2014-0377)”. The results described in the article have been obtained in the context of an internal collaboritive project supported by IFIMAC through MdM programme.