Optical anisotropy of near band-edge transitions in zinc oxide nanostructures

Optical anisotropy of the below and above band-edge transitions in three samples of well-aligned and tilted ZnO nanorods has been characterized using thermoreflectance (TR) and photoluminescence (PL) measurements in the temperature range between 30 and 300 K. The TR and PL spectra of the well-aligned nanorods with the largely top planes of {0 0 01} show considerable difference in energy with respect to those of the other tilted nanorods with the largely side planes of {1 0 1¯ 0}. Optical-axial anisotropy of the defects and band-edge excitonic transitions in the well-aligned and tilted ZnO nanorods are observed. Temperature dependences of transition energies of the defect emissions and band-edge excitons for the ZnO are analyzed. The crystallinity for the as-deposited ZnO thin films is also discussed.