Fyzikální ústav Akademie věd ČR

Electronic structure of graphene is closely related to the mechanical deformation and interactions with surroundings (i.e. with the supporting substrate). From a general point of view, it is driven by the intrinsic topography of the layer itself. We proposed a unique approach for custom modification of the graphene topography based on shaping of the single-layer graphene using monodisperse magnetic nanoparticles [1, 2]. Advanced processing of the atomic force microscopy (AFM) data revealed a linear dependence of the level of wrinkling on the concentration of the nanoparticles on the substrate. We also observed a distinctive fingerprint of the wrinkles in Raman spectra, which enables facile quantification of the wrinkling. We further discovered that for a specific particle geometry, tri-axial strain can be generated, which is a prerequisite for creation of giant magnetic pseudofields. The results are significant for various areas of graphene and 'beyond graphene' research, where the control of topography with nm precision is a crucial task, e.g. local chemical functionalisation, plasmonic localization, simulation of behaviour of the Dirac fermions in extreme regimes or development of nanosensors of harmful gases or biomolecules.

Fig.1.: Left: Topography of the substrate decorated with nanoparticles and single-layer graphene transferred over the substrate; visualized using atomic force microscopy (AFM) and scanning electron microscopy (SEM). Right: General correlation of the wrinkle graphene fraction (A_w) and the relative intensity of the principal Raman active mode related to the wrinkles. The decomposition of the G mode to the wrinkled (G2) and flat (G1) fraction is shown in inset.

References:
[1] J. Vejpravova, B. Pacakova, J. Endres, A. Mantlikova, T. Verhagen, V. Vales, O. Frank, M. Kalbac Graphene wrinkling induced by monodisperse nanoparticles: facile control and quantification, Sci. Rep. 5 (2015) 15061.
[2] B. Pacakova, J. Vejpravova, A. Repko, A. Mantlikova, M.Kalbac, Formation of wrinkles on graphene induced by nanoparticles: Atomic force microscopy study, Carbon 95 (2015) 537.

Research team: J.Vejpravová, B.Pacáková, T. Verhagen, A.Mantlíková