The optical anisotropy are considered in this paper, and we have studied ϵ 2(ω) under parallel polarization only, which is named as ϵ 2(ω)p. In Figure 5a, the pure (8,0) ZnO nanotubes have four peaks located at about 2.6, 8.3, 11.1, and 15.0 eV. The first peak located at 2.6 eV is mainly due to the transition from O 2p states
to Zn 4s states. The second peak at 8.3 eV corresponds to transitions between the Zn 3d Selleck GF120918 states and O 2p states. The peaks at 11.1 and 15.0 eV are associated with the electron transition between Zn 3d states and O 2s states. For the Ag1 configuration, the peak in the range from 5.0- to 13.0-eV energy region originates from the Zn 3d states to O 2p states and BIBF 1120 chemical structure Zn 3d states to O 2s states. The peak in the low-energy region at about 0.1 eV mainly comes from the electronic interband transition between Ag 4d states and Zn 4s states in the conduction band. The peak positions of the Ag1N2, Ag1N2,3,4, and Ag1N3,4 configurations are similar to that of Ag1 configuration
except that the peaks are more intense because of higher N concentration. The peak at about 2.0 eV originates from the electronic transition from Ag 4d states to Zn 4s states for Ag1 configuration while it originates from the electronic transition from Ag 4d to N 2p for Ag1N2, Ag1N2,3,4, Ag1N3,4, Ag1N5, and Ag1N6 configurations. A red shift occurred for the peak at about 0.5- to 2.0-eV energy region for the Ag1N2, GSK2245840 concentration Ag1N2,3,4, (-)-p-Bromotetramisole Oxalate and Ag1N3,4 configurations with the increase of N concentration, because the electron transition energy from the occupied impurity states
to CBM has a red shift, and the gap of the occupied impurity states to CBM are 0.395, 0.366, and 0.201 eV, respectively. Figure 5b shows the dielectric function spectra of Ag1N2, Ag1N5, and Ag1N6 configurations. In Figure 5b, the peak at 1.0- to 5.0-eV energy regions has a red shift, and the volume of the peak increases with the increasing distance of Ag atom and N atom. Figure 5 Dielectric function spectra of pure and Ag-N-codoped (8,0) ZnO nanotubes. (a) Configurations of Ag1, Ag1N2, Ag1N2,3,4, and Ag1N3,4. (b) Configurations of Ag1N2, Ag1N5, and Ag1N6. Figure 6 shows the reflectivity and absorption spectra of pure and Ag-N-codoped (8,0) ZnO nanotubes. For the reflectivity of the pure ZnO nanotube, four peaks (located at 2.5, 6.0, 8.0, and 11.6 eV, respectively) can be observed, which correspond to the ones at 2.6, 8.3, 11.1, and 15.0 eV in ϵ 2(ω), respectively. For the Ag1 configuration, there is a new transition peak near the Fermi energy levels because Ag is doped into the ZnO nanotube, and it is associated with the electron transition between Ag 4d states and O 2s states. However, the peak at about 2.