Tuning epitaxial graphene sensitivity to water by hydrogen intercalation

TL;DR

This study demonstrates that hydrogen intercalation enhances the water sensitivity of epitaxial graphene by increasing carrier concentration responsiveness and lowering hydrophobicity, making it promising for humidity sensor applications.

Contribution

It reveals that hydrogen intercalation improves humidity sensitivity and preserves carrier mobility in epitaxial graphene, advancing its use in sensor technology.

Findings

Increased humidity sensitivity in hydrogen-intercalated graphene

Retention of high carrier mobility at high humidity

Higher water sensitivity in monolayer graphene compared to bilayer

Abstract

The effects of humidity on the electronic properties of quasi-free standing one layer graphene (QFS 1LG) are investigated via simultaneous magneto-transport in the van der Pauw geometry and local work function measurements in a controlled environment. QFS 1LG on 4H-SiC(0001) is obtained by hydrogen intercalation of the interfacial layer. In this system, the carrier concentration experiences a two-fold increase in sensitivity to changes in relative humidity as compared to the as-grown epitaxial graphene. This enhanced sensitivity to water is attributed to the lowering of the hydrophobicity of QFS 1LG, which results from spontaneous polarization of 4H-SiC(0001) strongly influencing the graphene. Moreover, the superior carrier mobility of the QFS 1LG system is retained even at the highest humidity. The work function maps constructed from Kelvin probe force microscopy also revealed higher sensitivity to water for 1LG compared to 2LG in both QFS 1LG and as-grown systems. These results point to a new field of applications for QFS 1LG, i.e., as humidity sensors, and the corresponding need for metrology in calibration of graphene-based sensors and devices.