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Sci Adv. 2017 May 12;3(5):e1601724. doi: 10.1126/sciadv.1601724. eCollection 2017 May.

Backside absorbing layer microscopy: Watching graphene chemistry.

Author information

1
Laboratoire d'Innovation en Chimie des Surfaces et Nanosciences (LICSEN), Nanosciences et Innovation pour les Matériaux, la Biomédecine et l'Énergie, CEA, CNRS, Université Paris-Saclay, CEA Saclay, 91191 Gif-sur-Yvette cedex, France.
2
Institut Universitaire de Technologie de Saida, Université Libanaise, Saida, Lebanon.
3
Aix-Marseille Université, CNRS, Centrale Marseille, Institut Fresnel, F-13013 Marseille, France.
4
Institut des Molécules et Matériaux du Mans (UMR 6283), Equipe "Paysages Moléculaires, Horizons Biophotoniques," Université du Maine, Avenue Olivier Messiaen, F-72000 Le Mans, France.

Abstract

The rapid rise of two-dimensional nanomaterials implies the development of new versatile, high-resolution visualization and placement techniques. For example, a single graphene layer becomes observable on Si/SiO2 substrates by reflected light under optical microscopy because of interference effects when the thickness of silicon oxide is optimized. However, differentiating monolayers from bilayers remains challenging, and advanced techniques, such as Raman mapping, atomic force microscopy (AFM), or scanning electron microscopy (SEM) are more suitable to observe graphene monolayers. The first two techniques are slow, and the third is operated in vacuum; hence, in all cases, real-time experiments including notably chemical modifications are not accessible. The development of optical microscopy techniques that combine the speed, large area, and high contrast of SEM with the topological information of AFM is therefore highly desirable. We introduce a new widefield optical microscopy technique based on the use of previously unknown antireflection and absorbing (ARA) layers that yield ultrahigh contrast reflection imaging of monolayers. The BALM (backside absorbing layer microscopy) technique can achieve the subnanometer-scale vertical resolution, large area, and real-time imaging. Moreover, the inverted optical microscope geometry allows its easy implementation and combination with other techniques. We notably demonstrate the potentiality of BALM by in operando imaging chemical modifications of graphene oxide. The technique can be applied to the deposition, observation, and modification of any nanometer-thick materials.

KEYWORDS:

Chemistry; absorbing anti-reflection coating; functionalization; graphene; optical microscopy; real time imaging

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