Temperature-induced evolution of strain and doping in an isotopically labeled two-dimensional graphene - C^sub 70^ fullerene peapod

A two-dimensional peapod (2D-peapod) was engineered by sandwiching C70 fullerenes between two isotopically labeled graphene single-layers. Raman spectral mapping was used to investigate in-situ the evolution of strain and doping associated with topographic changes of the graphene layers in the temperature range 10-300 K. The isotope labeling of the top layer with 13C allowed us following the strain and doping in the bottom and top layer independently. The global behavior of the temperature dependence of the 12C (bottom) and 13C (top) graphene layer does not significantly deviates from that of an isotopically labeled graphene double layer. However, the presence of the C70 fullerenes give rise to the creation of specific networks of wrinkles in the top graphene layer, which significantly evolve with decreasing temperature. We propose that the C70 fullerenes adhered to the graphene layers act locally as a mutual mechanical coupler, and govern the local reconstruction of the topography of the 2D-peapod.