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Backside absorbing layer microscopy: Watching Graphene chemistry

Abstract : The rapid rise of 2-dimensional nanomaterials implies the development of new versatile, high-resolution visualization and placement techniques. For example a single graphene layer becomes observable on Si/SiO$_2$ 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 like Raman mapping, atomic force microscopy (AFM) or scanning electron microscopy (SEM) are more suitable to observe graphene monolayers. The two first are slow and the third one is operated in vacuum so that in all cases real-time experiments including notably chemical modifications are not accessible. Here, we introduce a new wide-field optical microscopy technique: Backside Absorbing Layer Microscopy (BALM), which uses Anti-Reflection and Absorbing (ARA) layers to achieve extreme contrast at an interface. It combines the vertical sub-nm sensitivity of an AFM with the versatility and real-time imaging capabilities of an optical microscope. We demonstrate that this technique allows imaging very easily 2D materials like graphene oxide and MoS$_2$ , both in air and in water, with extremely high resolution (see Figure). In addition, it also provides chemical contrast: we are notably able to clearly differentiate GO flakes from reduced graphene oxide flakes (r-GO) even though they only differ by the density of oxygen functions. BALM also permits to monitor surface reactions in situ. As examples, we followed the deposition of nanoparticles on GO and we took advantage of the high-resolution and real-time imaging of BALM to study the dynamics of the adsorption of small molecules on GO. Finally we show that, thanks to its favorable geometry, the BALM technique can be naturally combined with other techniques, notably electrochemistry and that its use is not limited to 2D materials.
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https://hal-cea.archives-ouvertes.fr/cea-02341727
Contributor : Serge Palacin <>
Submitted on : Thursday, October 31, 2019 - 3:05:21 PM
Last modification on : Wednesday, March 25, 2020 - 9:21:05 AM
Long-term archiving on: : Saturday, February 1, 2020 - 6:00:04 PM

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  • HAL Id : cea-02341727, version 1

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Stéphane Campidelli, R Abou Khachfe, K Jaouen, R. Cornut, Bruno Jousselme, et al.. Backside absorbing layer microscopy: Watching Graphene chemistry. GRD-I Graphene & Co, Oct 2017, Aussois, France. ⟨cea-02341727⟩

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