The Effect of Humidity on the Interlayer Interaction of Bi-layer Graphene

TL;DR

This study investigates how environmental humidity influences the interlayer interactions in bi-layer graphene, revealing that water intercalation affects vibrational properties and potentially alters layered material behavior.

Contribution

It provides new insights into the role of humidity and intercalated water molecules in modifying interlayer interactions in bi-layer graphene.

Findings

Intercalated water causes an additional vibrational peak in Raman spectra.

Monolayer water coverage increases with humidity up to 50% RH.

Humidity significantly influences interlayer interactions in layered materials.

Abstract

The lubricating ability of graphite largely depends on the environmental humidity, essentially the amount of water in between its layers. In general, intercalated molecules in layered materials modify their extraordinary properties by interacting with the layers. To understand the interaction of intercalated water molecules with graphene layers, we performed Raman measurements on bi-layer graphene at various humidity levels and observed an additional peak close to that of the low-frequency layer breathing mode between two graphene layers. The additional peak is attributed to the vibration between an intercalated water layer and the graphene layers. We further propose that the monolayer coverage of water increases between bilayer graphene with increasing environmental humidity while the interaction between the water layer and graphene layers remains approximately unchanged, until too much water is intercalated to keep the monolayer structure, at just over 50\% relative humidity. Notably, the results suggest that unexpectedly humidity could be an important factor affecting the properties of layered materials, as it significantly modifies the interlayer interaction.