Author(s)

Bridinette Thiodjio Sendja^1*, Rolant Eba Medjo², Jeannot Mane Mane¹, Germain Hubert Ben-Bolie³, Pierre Owono Ateba³

¹Ecole Nationale Supérieure Polytechnique (National Advanced School of Engineering), Department of Mathematics and Physical Sciences, University of Yaoundé I, Yaounde, Cameroon.
²Physics Department, Faculty of Science, University of Douala, Douala, Cameroon.
³Physics Department, Faculty of Science, University of Yaoundé I, Yaounde, Cameroon.

Carbon nanotubes (CNTs) grown on plain substrates SiO2/Si(100) by a direct current and hot filaments catalytic chemical vapor deposition process have been studied by synchrotron X-ray absorption near edge spectroscopy (XANES) technique to theoretically investigate the angular-dependence of carbone (C) K-edge π* and σ* transitions. Experimental XANES spectra show that π* resonance increases with the incidence angle from normal to grazing incidence angle while σ* resonance decreases. This has been explained by the sine-square and cosine-square dependencies of π* and σ* intensities, respectively. These results were confirmed by theoretical XANES curves of highly oriented pyrolytic graphite (HOPG) and CNTs plotted versus incidence angle. It has been shown that π* and σ* transitions strongly depend on the nature of polarized light (linearly or circularly). At the linear polarized light, π* resonance is a preference as well as at right-circular polarized. At the left-circular polarized light, σ* resonance is a preference. The π* intensities are high at parallel orientation and the σ* intensities are low at normal orientation. The smallest π* intensity is noticed at normal orientation, where the π* orbitals are supposed to be lying parallel to the surface plane for perfectly aligned HOPG or CNTs. This explains the incomplete extinction of π* intensity. We noticed at parallel orientation a region where any π* and σ* transitions did not expect because of the lack of polarization light.

Angular Dependence, XANES, Normal Incidence, Grazing Incidence, Carbon Nanotubes, Intensity

Sendja, B. , Medjo, R. , Mane, J. , Ben-Bolie, G. and Ateba, P. (2015) Theoretical Investigation of X-Ray Absorption near Edge Spectroscopy (XANES) Angular Dependence of Aligned Carbon Nanotubes Grown by DC HF CVD Process. Materials Sciences and Applications, 6, 373-390. doi: 10.4236/msa.2015.65043.