Imaging of edge inactive layer in micro-patterned graphene monolayer

An electrically inactive layer (EIL) near the edge of micro-patterned graphene lines was investigated using both scanning microwave microscopy (SMM) and Raman spectroscopy. Monolayer graphene sheets grown by chemical vapor deposition (CVD) were transferred from the copper foil growth substrate to different substrates, and structured into periodic lines using lithography and oxygen plasma etching. SMM images were recorded at half- and quarter- wavelength resonances showing distinguished imaging contrast of the EIL from the center of the graphene lines. The width of the EIL is determined around 0.17 μm. Correlation of the SMM imaging contrast indicates that the local electrical conductivity of the EIL is significantly reduced, which agrees with Raman spectroscopic images.