Abstract
C. Melios et al. Nanoscale, 2017,9, 3440-3448 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.