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Self-Standing Graphene Sheets Prepared with Chemical Vapor Deposition and Chemical Etching 13 With decreasing the incident electron energy, the atomic vibration amplitudes became larger due to the high sensitivity of the graphite surface. This indicates that the thermal vibrational amplitudes of surface atoms are larger than that of the bulk crystal interior. However, the surface phonon dispersion curves of graphite measured with HREELS are almost the same in bulk. Hence, only the origin of the large vibrational ampulitude indicated by LEED is attributed to the phonons at long wavelength as comapred with atomic distance. These phonons cannot be detected by HREELS because their wave vectors are too small around Γ point, and their vibrational energires are too low . That is to say, whole the surface sheet moves largely, which is in good agreement with the direct observations of wrinkle motion. We concluded that the second-layer seems to grow at the interface, vibrating and stretching the wrinkles. In addition, if there are many grain boundaries in the second-layer, the wrinkle stretch easily stops at the boundaries. Since the wrinkle motion continued during the growth of the second layer, the single-domain second layer might grow in large scale. Fig. 11. The effective mean-square atomic vibration amplitudes of graphite(0001) surface as a function of electron energy (see Wu et al., 1985). 3. Self-standing graphene sheets Additional chemically etching the Ni substrate made it possible to separate macroscopic self-standing graphene sheets with a few tenth mm in size (Odahara et al., 2009). Self- standing sheets could be the ideal sample support of organic materials for TEM observations. Low-energy electron microscope together with holder made of graphene sheets seems to be promising for observation of organic- and/or bio-materials. Fig. 12 shows a typical TEM images (a) of the carbon aggregates at 100 kV. Because we detected only the spots of graphene sheets in diffraction patterns, we concluded that the observed materials are composed of multi-folding graphene sheets. In Fig. 12 (a), thePDF Image | GRAPHENE SYNTHESIS CHARACTERIZATION PROPERTIES
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