Electrical and structural properties of Aligned Aluminum-doped zinc oxide nanorod arrays via a novel sonicated sol-gel immersion

Aligned Aluminum (Al)-doped zinc oxide (ZnO) nanorod arrays were prepared on seeded catalyst-coated glass substrates using a novel technique of sonicated sol-gel immersion method at different annealing temperatures. The diameter sizes of synthesized hexagonal-shaped nanorods are found to be in the range between 50 nm to 150 nm. The annealing treatment up to 500°C did not give any significance effects on the nanorods morphology as observed by field emission scanning electron microscopy (FESEM). The micro-Raman spectra reveal that the crystallinity of the nanorod arrays were improved at higher annealing temperature as shown by the E₂ (high) peak intensity enhancement. This result was supported by XRD spectra where the XRD peak intensity for annealed nanorods is higher than as-grown nanorods. XRD spectra reveal Al-doped ZnO nanorod arrays grew preferentially along the (002) plane or the c-axis, indicating high quality of the ZnO crystal. Al forms Ohmic contacts with Al-doped ZnO nanorod arrays that are shown through a linear current-voltage (I-V) characteristic. The conductivity of nanorod arrays increased with annealing temperatures up to 500°C with a maximum conductivity ~1.72 × 10^-2 Scm^-1.