Optical Properties of Anatase and Rutile Phase TiO2 Nanotubes

• Author / Creator

  Zhang, Yun

• Nanofabricated optically anisotropic uniaxial thin films with deep submicron feature sizes are emerging as potential platforms for low-loss all-dielectric meta-materials and for Dyakonov surface wave-based sub-wavelength optical confinement and guiding at interfaces with isotropic media. In this context, we fabricated anatase and rutile phased titania nanotube arrays (TNTAs) and investigate the optical properties of one such uniaxial platform, namely self-organized TNTAs grown by the bottom-up nanofabrication process of electrochemical anodization on silicon wafer substrates. Transmittance spectra measurement was used to investigate the isotropic properties of TNTAs, refractive index was extracted from the spectra fringes. Variable angle spectroscopic ellipsometry was used to investigate the optical anisotropy in two phases of TNTAs. One phase is anatase and the other phase contains a mixture of anatase and rutile. Both kinds of TNTAs were found to have positive birefringence (n). The experimentally measured anisotropy in the refractive index of the TNTAs was compared with model-predictions of two different effective medium approximations incorporating the uniaxial geometry. The measured value of n for anatase-phase TNTAs exceeded that of bulk anatase single crystals, indicating the potential of nanostructured dielectrics to outperform dielectric crystals of the same material with respect to the magnitude of the achievable directional refractive index contrast.

• Subjects / Keywords

  • Nanotube arrays
  • Anisotropy
  • Ellipsometry
  • Titanium dioxide
  • Anatase
  • Polarized light
  • Rutile
  • Refractive index
  • Birefringence

• Graduation date

  Fall 2017

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R37P8TT2M

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.