New Concepts for Production of Scalable Single Layer Oxidized Regions by Local Anodic Oxidation of Graphene

• Published in: Small (Weinheim an der Bergstrasse, Germany) Germany), 2019-10, Vol.15 (40), p.e1902817-n/a
• Main Authors: Quesada, Sergio J., Borrás, Fernando, García‐Vélez, Miguel, Coya, Carmen, Climent, Esteban, Munuera, Carmen, Villar, Ignacio, la Peña O'Shea, Víctor A., Andrés, Alicia, Álvarez, Ángel L.
• Format: Article
• Language: English
• Subjects: Anodizing; Carrier mobility; Electric bridges; Electrical measurement; Faradaic current; First principles; Graphene; graphene oxide; local anodic oxidation; Micrometers; Monolayers; Nanotechnology; Oxidation; Photoelectrons; Transient current; Two dimensional materials
• ISSN: 1613-6810; 1613-6829
• DOI: 10.1002/smll.201902817

A deep comprehension of the local anodic oxidation process in 2D materials is achieved thanks to an extensive experimental and theoretical study of this phenomenon in graphene. This requires to arrange a novel instrumental device capable to generate separated regions of monolayer graphene oxide (GO) over graphene, with any desired size, from micrometers to unprecedented mm2, in minutes, a milestone in GO monolayer production. GO regions are manufactured by overlapping lots of individual oxide spots of thousands µm2 area. The high reproducibility and circular size of the spots allows not only an exhaustive experimental characterization inside, but also establishing an original model for oxide expansion which, from classical first principles, overcomes the traditional paradigm of the water bridge, and is applicable to any 2D‐material. This tool predicts the oxidation behavior with voltage and exposure time, as well as the expected electrical current along the process. The hitherto unreported transient current is measured during oxidation, gaining insight on its components, electrochemical and transport. Just combining electrical measurements and optical imaging estimating carrier mobility and degree of oxidation is possible. X‐ray photoelectron spectroscopy reveals a graphene oxidation about 30%, somewhat lower to that obtained by Hummers' method. This work presents a method to manufacture 2D graphene/graphene oxide monolayer structures of unprecedented size (>mm2) using an innovative equipment. This size allows the exhaustive chemical characterization of the new material and the theoretical modeling of both its expansion and the generated electric current. These contributions constitute actual milestones in the field of local oxidation of 2D materials.