Growth of Al:ZnO nano-flowers by pulsed laser ablation deposition

Aluminium-doped (3%) zinc oxide thin films (AZO) were prepared, using pulsed laser deposition, with varying deposition times. The target was fabricated from compacted aluminium-doped zinc oxide nano-powder produced by sol-gel. The films had a growth consisting of nanostructures in the form of columns with sharp ends which, for certain deposition times, resemble nano-flowers or nano-leaves. The small spheroid-like particles created during columnar growth act as a seed for other AZO needles, resulting in the appearance of lotus-like flowers and even smaller needles growing from the petals. The deposition time was found to have a significant effect on the properties of the ZnO films. Specifically, the thickness of the films increased monotonically with deposition time until it reached a maximum value at 30 min. X-ray diffraction analysis revealed that the films were composed of polycrystalline ZnO with a hexagonal wurtzite structure. The preferred orientation and crystallite size also exhibited a similar trend with deposition time; thus, grain size shows a maximum at 30 min of deposition, where the preferred orientation changes from 103 to 002. Regarding optical properties, the bandgap energy of the ZnO films displayed a non-monotonic trend with deposition time, increasing for the sample deposited for 20 min but above this deposition time, although the obtained value exhibits a slight tendency to decrease, taking into account the confidence interval, the bandgap remains similar. This study demonstrates that careful control of deposition time is critical for achieving desirable properties of Al doped ZnO films. These observations have important implications for potential applications of the ZnO films in solar cells, antibacterial, and photocatalytic activities. The findings of this work pave the way for the design and optimization of ZnO-based materials for various applications.