Polarized absorption spectra of (2,2) carbon nanotubes aligned in channels of an AEL crystal

Abstract We report polarized absorption spectra for the (2,2) tubes arrayed in the one-dimensional channels of an AlPO 4 -11 (AEL) single crystal. Strong polarization dependence is observed indicating a preferential optical dipole along the axis of carbon nanotubes. By correlating with the absorption spectra and First-principles local density function (LDA) calculation, the absorption peak at 2.95 eV is uniquely assigned to semiconducting type (2,2) tubes, and peaks at 2.67 and 2.40 eV are corresponding to metallic type (2,2) tubes.