Effects of Π-electron in humidity sensing of artificially stacked graphene bilayers modified with carboxyl and hydroxyl groups

In this study, we investigate humidity sensing performance of an artificially stacked graphene bilayers (ASGBs). Compared with non-modified ASGBs, the humidity sensing response of the ASGBs modified by a low-damage plasma (LD-plasma) can be improved by 40% and sensing selectivity to ethanol can be enhanced by 35% in our experimental results. Under examinations of Raman and XPS, these improvements can be attributed to carboxyl and hydroxyl groups bonding on the ASGBs surface after LD-plasma treatments. As a consequence, the ASGBs π-electron characteristic, which offers the main sensing mechanism, are also modified by the bonding groups. Therefore, these modifications not only help adsorptions of water molecules but also improve humidity selectivity to ethanol and IPA. Based on these developments and characterizations, this work developed a LD-plasma modified ASGBs sensing material for humidity sensing applications.