Aram Mailian1,2, Zhozef Panosyan2, Yeremia Yengibaryan2, Manuel Mailian3 1 Institute for Informatics, 1 P. Sevak str., 0014, Yerevan, Armenia 2 State Engineering University, 105, Teryan str. Yerevan, Armenia 3 LTX-Credence Armenia, 2 Adonts str., 0014, Yerevan, Armenia ![]() The optical absorption in as-obtained CTL exposes a resonance in ultraviolet (at 4.8 eV), which refers to excitonic transitions and is assumed to be a fingerprint of sp2 structure [1]. With step-by-step removal (peeling) of topmost layers of CTL the peak in absorption fades out whereas the absorption above ~5 eV progressively dominates the optical absorption spectrum. The latter is characteristic to sp3 carbon allotrope. X-ray diffraction (XRD) study also reveals a crystalline structure on the CTL surface. The XRD pattern has a (002) diffraction peak at 2=26.5510 emerging over a broad noise background. No additional feature is observed. Such a pattern is characteristic of two-layer graphene [2]. With the removal of surface layer of CTL the peak on XRD pattern disappears leaving only the flat background. Evidently X-ray diffraction is enabled by a periodical crystalline structure on the CTL surface. In Raman spectra, the width and symmetrical line shape of 2D band, the equal peak intensity of G and 2D peaks, reveal that the observed features are characteristic to the crystal lattice of turbostratic sp2 carbon [3]. Observed features in combination with other observations testify that the CTL is morphologically anisotropic through the layer thickness; sp2 phase of turbostratic bi-layer grapheme is formed at the top, and thicker sp3 allotrope sub-layer is formed beneath it. [1] K.F. Mak, et al. Sol. St. Comms. 152 (2012) 1341-1349. [2] Z. Q. Li et al. Carbon 45, 8, (2007) 1686–1695. [3] M. S. Dresselhaus et al. Phil. Trans. R. Soc. A (2010) 368, 5355–5377. ![]() |
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