Controlled wrinkling of single-layer graphene (1-LG) at nanometer scale was achieved by introducing monodisperse nanoparticles (NPs), with size comparable to the strain coherence length, underneath the 1-LG. Typical fingerprint of the delaminated fraction is identified as substantial contribution to the principal Raman modes of the 1-LG (G and G’). Correlation analysis of the Raman shift of the G and G’ modes clearly resolved the 1-LG in contact and delaminated from the substrate, respectively. Intensity of Raman features of the delaminated 1-LG increases linearly with the amount of the wrinkles, as determined by advanced processing of atomic force microscopy data. Our study thus offers universal approach for both fine tuning and facile quantification of the graphene topography up to ~60% of wrinkling.
Topography of nanoparticle-treated substrate (NPs) and graphene monolayers transferred to SiO2 / Si substrate; shown by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Bottom left: detail of the graphene monolayer topography transferred to the nanoparticle substrate, showing the AFM and the associated Fourier image, which shows the preferential orientation of the wrinkles. Bottom right: A general correlation between the wrinkled graphene fraction (Aw) and the relative intensity of the pivotal Ramansian active mode of the graphene associated with the wrinkled layer. In detail, the G mode decomposition into a wrinkled (G2) and smooth (G1) fraction is shown.