First-principles studies of water adsorption on graphene: The role of the substrate

TL;DR

This study uses first-principles calculations to explore how water molecules affect the electronic properties of graphene, especially when supported on a SiO2 substrate, revealing substrate-dependent doping effects.

Contribution

It demonstrates that the substrate significantly influences water-induced doping in graphene, highlighting the importance of substrate properties in graphene-water interactions.

Findings

Water has minimal effect on suspended graphene's electronic properties.

On defective SiO2 substrates, water can induce doping by shifting impurity bands.

Substrate properties critically determine water's impact on graphene's electronic behavior.

Abstract

We investigate the electronic properties of graphene upon water adsorption and study the influence of the SiO2 substrate in this context using density functional calculations. Perfect suspended graphene is rather insensitive to H2O adsorbates, as doping requires highly oriented H2O clusters. For graphene on a defective SiO2 substrate, we find a strongly different behavior: H2O adsorbates can shift the substrate's impurity bands and change their hybridization with the graphene bands. In this way, H2O can lead to doping of graphene for much lower adsorbate concentrations than for free hanged graphene. The effect depends strongly on the microscopic substrate properties.