Water Affinity to Epitaxial Graphene: The Impact of Layer Thickness

Abstract

The sensitivity to water vapour of one-, two-, and three-layer epitaxial graphene (1, 2, and 3LG) is examined in this study. It is unambiguously shown that graphene's response to water, as measured by changes in work function and carrier density, is dependent on its thickness, with 1LG being the most sensitive to water adsorption and environmental concentration changes. This is furthermore substantiated by surface adhesion measurements, which bring evidence that 1LG is less hydrophobic than 2LG. Yet, surprisingly, it is found that other contaminants commonly present in ambient air have a greater impact on graphene response than water vapor alone. This study indicates that graphene sensor design and calibration to minimize or discriminate the effect of the ambient, in which it is intended to operate, are necessary to insure the desired sensitivity and reliability of sensors. The present work will aid in developing models for realistic graphene sensors and establishing protocols for molecular sensor design and development.

Probing exciton species in atomically thin WS2–graphene heterostructures

“…The two components are associated with the emission from neutral exciton states at 1.93 eV, with the peak FWHM of 30 meV, and from charged exciton states (trions) at 1.9 eV and peak FWHM of 50 meV. The formation of trions requires an electron-or hole-rich environment, which is provided for WS 2 /2LG by the interaction with graphene, and owing to the higher carrier density in 2LG compared to 1LG, as confirmed by previous transport experiments and calculations [17,23].…”

In-situ terahertz optical Hall effect measurements of ambient effects on free charge carrier properties of epitaxial graphene

“…The intrinsic electron doping of pristine monolayer epitaxial graphene on Si-face SiC was found to be on the order of 10 13 cm −2   6 . The polarity of the Si-face SiC also gives rise to high hydrophilicity, which is relatively unchanged with addition of a graphene monolayer 15 .…”

Excitonic Effects in Tungsten Disulfide Monolayers on Two-Layer Graphene

“…Refs. [25,26,27,36]. The surface potential map of bare graphene probed by SKPM shows regions with two main distinct contrast levels: a bright one, given by small patches formed at the edge of the terraces, associated with 2LG, superimposed on a dark contrast background of onelayer graphene (1LG) ( Figure 1d).…”