▎ 摘　　要

Graphene flakes with various sizes are prepared directly on SiO2/Si substrate using a remote catalytic method. The flakes are characterized by Raman spectra, and the peak of the 2D band shows a drastic blue shift due to the in-plane compressive strain induced by the different coefficients of thermal expansion between the graphene and the substrate. More importantly, the compressive strain of the flake is found to increase with flake size. The behavior can be understood by the strain releasing through the defects and the edge of graphene flakes. Additionally, we find that the defects contribute more than 75% of strain relaxation for all graphene samples, and the width of the edge region for the strain relaxation increases from similar to 50 to similar to 110 nm for 2 and 5 h grown flakes. Our finding indicates that the compressive strain inevitably exists in the as-grown graphene on SiO2/Si, which may be eliminated through a new preparation method.