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Register a new userSize dependence of the Graphene Islands Moving on Cu (111) Surface during the CVD Growth
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The graphene islands, formed as different sizes, are crucial for the final quality of the formed graphene during the CVD growth either as the nucleation seeds or as the build blocks for larger graphene domains. Extensive efforts had been devoted to the size or the morphology control while fewer works were reported on the moving dynamics of these graphene islands as well as the associate influences to their coalescence during the CVD Growth of graphene. In this study, based on the self-developed C-Cu empirical potential, we performed systematic molecular dynamics simulations on the surface moving of three typical graphene islands CN (N = 24, 54 and 96) on the Cu (111) surface and discovered their different behaviors in sinking, lateral translation and rotation at the atomic scale owning to their different sizes, which were proved to bring forth significant impacts to their coalescences and the final quality of the as-formed larger domains of graphene. This study would deepen our atomistic insights into the mechanisms of the graphene CVD growth and provide significant theoretical guidelines to its controlled synthesis.
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We present a study of graphene/substrate interactions on UHV-grown graphene islands with minimal surface contamination using emph{in situ} low-temperature scanning tunneling microscopy (STM). We compare the physical and electronic structure of the sample surface with atomic spatial resolution on graphene islands versus regions of bare Cu(111) substrate. We find that the Rydberg-like series of image potential states is shifted toward lower energy over the graphene islands relative to Cu(111), indicating a decrease in the local work function, and the resonances have a much smaller linewidth, indicating reduced coupling to the bulk. In addition, we show the dispersion of the occupied Cu(111) Shockley surface state is influenced by the graphene layer, and both the band edge and effective mass are shifted relative to bare Cu(111).
We present a scanning tunneling microscopy (STM) study of native defects in graphene islands grown by ultra-high vacuum (UHV) decomposition of ethylene on Cu(111). We characterize these defects through a survey of their apparent heights, atomic-resolution imaging, and detailed tunneling spectroscopy. Bright defects that occur only in graphene regions are identified as C site point defects in the graphene lattice and are most likely single C vacancies. Dark defect types are observed in both graphene and Cu regions, and are likely point defects in the Cu surface. We also present data showing the importance of bias and tip termination to the appearance of the defects in STM images and the ability to achieve atomic resolution. Finally, we present tunneling spectroscopy measurements probing the influence of point defects on the local electronic landscape of graphene islands.
This paper has been withdrawn by first author KM Seemann.
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