Abstract

The band-edge excitonic transitions of vertically aligned and tilted $\mathrm{ZnO}$ nanorods on sapphire have been characterized using thermoreflectance (TR) measurements in the temperature range between 30 and $300\mathrm{K}$. The TR spectra of the nanorods with largely $\left\{0001\right\}$ planes show considerable difference in energy and line shape with respect to those of the other sample with largely side planes of $\left\{10\overline{1}0\right\}$. The TR result at each temperature clearly indicates the band-edge excitons (A, B, and C) measured from the largely $\left\{0001\right\}$ planes of the rods are lower in energy with respect to those obtained from the other sample dominated by the side planes of $\left\{10\overline{1}0\right\}$. Optical anisotropy in the transition amplitudes of the TR spectra for the vertically aligned and tilted $\mathrm{ZnO}$ nanorods is observed. The TR is shown to be very sensitive to the detection of the $\mathrm{ZnO}$ nanorods’ alignment.

© 2007 Optical Society of America

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