Vertically Grown Carbon Nanostructure Alignment: An Investigation by Using X-Ray Absorption Spectroscopy

This paper describes XRay Absorption Spectroscopy (XAS) on the carbon K edge of carbon nanostructures (nanotubes, nanofibers, and nanowalls). They are grown using a Plasma and Hot Filamentsenhanced Catalytic Chemical Vapor Deposition (PE HF CCVD) process on plain SiO2(8 nm thick)/Si(100) substrates. The XAS spectra are extremely sensitive to prior thermal treatment, as intense adsorption on the outer wall of the nanotubes can significantly affect the absorption transitions. SEM, TEM, and Raman spectroscopy are used to characterize the morphology and nature of these carbon nanostructures. Carbon nanotubes are formed based on the conditions of catalyst preparation and the DC HF CCVD process (CNTs), The angular dependence of incident light and the geometrical morphology of the nanostructures cause wide variations in the C Kedge intensity of transitions to the empty and states. A full lineshape analysis of the XAS spectra was performed using homemade software, allowing the relative proportion of and transitions to be estimated. A geometrical model of the angular dependence of light incidence angle and morphology of carbon nanostructures is developed. With reference to the HOPG (Highly Oriented Pyrolytic Graphite) case, A degree of alignment that is representative of the localized orientation of the graphitic carbon bonds can be extracted, accounting not only for the overall orientation, but also for local defects such as impurities incorporation, structural defects, and so on. This level of agreement is consistent with SEM observations. Thus, CNT films exhibit degrees of alignment of around 50%, depending on the occurrence of defects during the growth process, whereas no special alignment can be detected with CNFs and CNPs, and a weak one (around 20%) is detected with CNWs.

Author (S) Details

Jeannot Mane Mane
IPCMS, UMR 7504 CNRS, Strasbourg, France and Ecole Nationale Supérieure Polytechnique (National Advanced School of Engineering), Department of Mathematics and Physical Sciences, The University of Yaoundé I, Yaounde, Cameroon.

François Le Normand
IPCMS, UMR 7504 CNRS, Strasbourg, France.

Rolant Eba Medjo
Physics Department, Faculty of Science, University of Yaoundé I, Yaounde, Cameroon and Physics Department, Faculty of Science, University of Douala, Douala, Cameroon.

Costel Sorin Cojocaru
IPCMS, UMR 7504 CNRS, Strasbourg, France.

Ovidiu Ersen
IPCMS, UMR 7504 CNRS, Strasbourg, France.

Antoine Senger
IPCMS, UMR 7504 CNRS, Strasbourg, France.

Carine Laffon
LURE, UMR CNRS, Centre Universitaire Paris Sud, Orsay, France.

Bridinette Thiodjio Sendja
Ecole Nationale Supérieure Polytechnique (National Advanced School of Engineering), Department of Mathematics and Physical Sciences, The University of Yaoundé I, Yaounde, Cameroon and Physics Department, Faculty of Science, University of Yaoundé I, Yaounde, Cameroon.

César Mbane Biouele
Physics Department, Faculty of Science, University of Yaoundé I, Yaounde, Cameroon.

Germain Hubert Ben-Bolie
Physics Department, Faculty of Science, University of Yaoundé I, Yaounde, Cameroon.

Pierre Owono Ateba
Physics Department, Faculty of Science, University of Yaoundé I, Yaounde, Cameroon.

Philippe Parent
LURE, UMR CNRS, Centre Universitaire Paris Sud, Orsay, France.

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