Stacked AA graphite has been synthesized using a high-density dc plasma in hydrogen-methane mixtures. Graphene layers have been grown epitaxially with 2-1 registration between the AA graphitic edges and the (111) surface of diamond. In addition, a new graphite crystal structure containing AA(') graphene layers, where alternate planes are translated by half the hexagon width, is formed by 1-1 registry. The resulting interplanar distances of the AA graphite at the interface range from 2.20 A for the 1-1 registration to 4.40 A for the 2-1 registration and have been measured directly by high-resolution transmission electron microscopy (TEM). The appearance of the characteristic d-spacings, 3.55, 2.15, 1.80, 1.75 (not fully resolved), and 1.25 A in the selective area diffraction patterns from the TEM, are consistent with reflections from the (001), (100), (102), (002), and (110) planes of the AA graphite. Simulation of the diffraction patterns, employing the structural factors of graphene, confirms the existence of AA graphite.

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Herein a method is proposed for engineering the electronic properties of diamond via surface hybridization with graphene.

The structure of multi-wall carbon nanotubes has been attributed previously to disordered stacking of the graphene planes. Evidence is presented that the nanotubes analyzed in this paper occur with stacked graphene layers in the sequence of AA′, where alternate graphene planes are translated by half the hexagon width. We further present proof that the crystalline materials comprise graphene helices (∼5 nm in width), rather than in the form of a perfect tube. We also show that the structural model proposed here may be a common structure for multi-wall carbon nanotubes.

Raman spectra of single-wall carbon nanotubes (SWNTs) exhibit a unique radial breathing mode (RBM) band (∼100−300 cm −1 ) and a G − peak (∼1570 cm −1 ), along with a D band (∼1350 cm −1 ). We show that the typical Raman signals for SWNTs are the signature of their helical structure determined using density functional theory simulation and structural analysis for hydrogenated and dehydrogenated SWNT samples. We demonstrate that the G − mode at ∼1570 cm −1 is unique to opened tubular graphene structures of ∼2 nm diameter. We also demonstrate that the D mode of ∼1350 cm −1 is originated from edge defects of opened SWNTs, revealing strong eigenvectors, which is absent in concentric tubes. We also report a radial−tangential mode (RTM) for concentric and opened SWNTs, which appears following RBM. We also interpret the low-energy Raman signal, reported as an RBM band, to be convolution of "localized RBM" (∼170 cm −1 ) and RTM (∼190 cm −1 ) for helical SWNTs. We also show that the analysis of the Raman spectra of SWNTs is consistent with general understanding on Raman analysis of carbon materials.