Where is the water? Nanoscale Mapping of Intercalated Water in Graphene Using Torsional Resonance Atomic Force Microscopy

Session

Poster Session Two

Authors

Mr. Sanket Jugade (1), Dr. Prosenjit Sen (1), Dr. Akshay Naik (1)

Affiliations

1. Indian Institute of Science

Keywords

graphene, intercalated water, TR AFM, TR phase, screening

Abstract text

Exfoliation of graphene in an ambient environment leads to trapping of liquid between graphene and a hydrophilic substrate [1]. The interfacial ice-like water layer significantly modifies graphene's tribological [2] and electronic properties [3]. The confined water also governs several other properties like adhesion, surface chemistry, conductance, and local strain in graphene. Visualizing micron-scale islands of trapped liquid is possible through topography in Atomic Force Microscopy (AFM). However, localized mapping of the sub-surface liquid regions is not easy. In this work, we show Torsional Resonance AFM phase-contrast as a simple tool to enable nanoscale mapping of intercalated water in graphene. TR phase remains nearly the same on SiO₂ and graphene with intercalated water, while it it ∼1°-3° less on graphene without intercalated water. This technique probes the graphene-liquid interface in non-invasive way nonetheless extremely sensitive to near-field lateral forces. The TR phase-contrast most likely arises due to the screening ability of graphene. Variation in phase-contrast with tip-sample distance shows the opacity of graphene to tip and SiO₂ van der Waals interaction, whereas its transparency to tip and hydrogen-bonded water interaction. Furthermore, we utilize this TR phase mapping technique to study the effect of moisture intrusion and thermal processing on the intercalated water in graphene. This work would help in performing further experimental studies to probe various interesting properties of the intercalated liquid in graphene and other 2D materials.

References

[1] Ochedowski, O. et al. Sci Rep (2014)

[2] Lee et al. J. Phys. Chem. Lett. (2017)

[3] Shim J. et al. Nano Lett. (2012)