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Zinc-oxide (ZnO) nanorod arrays were successfully prepared by using dual sonication sol–gel process. Field emission scanning electron microscopy revealed that the nanorods exhibited a hexagonal structure with a flat-end facet. The nanorods displayed similar surface morphologies and grew uniformly on the seed layer substrate, with the average diameter slightly increasing to the range of 65 to 80 nm after being immersed for varying growth times. Interestingly, thickness measurements indicated that the thicknesses of the samples increased as the growth time was extended. In addition, the X-ray diffraction spectra indicated that the prepared ZnO nanorods with a hexagonal wurtzite structure grew preferentially along the c-axis. Therefore, we can conclude that the diameter, length, and orientation of the ZnO nanorod arrays along the c-axis are controllable by adjusting the growth time, motivating us to further explore the growth mechanisms of ZnO nanorods.

Metal–semiconductor–metal (MSM) ultraviolet (UV) photoconductive sensors were fabricated using undoped and aluminium (Al)-doped zinc oxide (ZnO) nanorod arrays prepared via the sonicated sol–gel immersion method. Notably, the nanorod diameter decreased with Al-doping, varying in the size range of 30 to 70 nm, compared with undoped ZnO, which had a size range of 80–120 nm. The Al-doped nanorod arrays exhibited optical properties superior to those of the undoped ZnO, with an average transmittance of 85% in the visible region; the Al-doped arrays also showed good UV absorption properties. Photoluminescence measurements indicate that the suppression of defects was observed for the Al-doped ZnO nanorod, as shown by a bigger I UV/I vis of 1.24 compared to that of undoped ZnO (0.97). According to the experimental results, the UV responsivity was significantly improved by the Al-doping, with the highest value of 373 A/W obtained at an inter-electrode distance of 0.07 mm under UV light (365 nm, 750 µW/cm2) with a 10 V bias. In addition, the responsivity of the UV sensor also significantly improved when the inter-electrode distances were reduced from 2.00 to 0.07 mm.

Aluminium (Al)-doped zinc-oxide (ZnO) nanorod arrays have been successfully prepared using a novel and low-temperature sonicated sol–gel immersion method. The photoluminescence (PL) spectrum reveals the appearance of two emission peaks from the nanorod that are centred at 381 and 590 nm. The nanorod has a hexagonal structure with a flat-end facet, as observed using field-emission electron microscopy (FESEM). Interestingly, all samples have similar surface morphologies and diameter sizes of 40 to 150 nm after immersion in different precursor-solution volumes. The thickness-measurement results show that the thicknesses of the samples increase after immersion in higher precursor-solution volumes. We show for the first time that the growth of nanorod arrays along the c-axis can be controlled using different precursor volumes, and its growth mechanism is discussed. X-ray diffraction (XRD) spectra indicate that the prepared nanorods are ZnO with a hexagonal wurtzite structure that grows preferentially along the c-axis.

Novel vertically aligned carbon nanotubes (VACNTs) were successfully grown on Mg0.3Zn0.7O thin film template. Current–voltage (I–V) characteristics of both VACNTs and VACNTs/Mg0.3Zn0.7O were measured where it first demonstrates that highly conductive VACNTs with more than 1 ×105 S cm-1 were achieved using Mg0.3Zn0.7O thin film template, though both samples showing only a small difference in the micro-Raman spectroscopy. This suggested that the used of Mg0.3Zn0.7O thin film template is capable of promoting the growth of VACNTs to have a smaller diameter and blocked the electrons' penetration into silicon that leads to highly conductive sample.