Variation in the c-axis conductivity of multi-layer graphene due to H2 exposure.

The variation of the c-axis conductivity of a multilayer graphene (MLG) as a function of H2 pressure from vacuum to 20 bar has been investigated. MLG was connected to the electrodes vertically using a wet transfer process. After exposure to H2 gas pressure up to 20 bar, the chemisorption of dissociated atomic hydrogen on MLG affects its electrical and structural properties. The formation of C-H bonds causes a decoupling of graphene layers, and then interferes with charge transfer through the out of plane. As a result, the c-axis conductivity decreases. Furthermore, the electron doping effect and the decoupling of the layers were confirmed using Raman spectroscopy. Hydrogenated carbons induce a defect structure of MLG which results in the expansion of layers. We observed a 43.54% increase in the thickness of the MLG after H2 exposure using atomic force microscopy.