Atmospheric Pressure Chemical Vapor Deposition Grown One-Dimensional ZnO Nanostructures

Abstract

One-dimensional (1D) zinc oxide (ZnO) nanostructures (NSs) as nanowires (NWs) and columnar nanoflakes (NFs) were prepared by atmospheric pressure chemical vapor deposition (APCVD) system. The effect of different thermal treatment times (0, 1, 2, and 3 h) on the physical properties of the grown ZnO NWs was methodically investigated. Further, the surface morphology of such 1D ZnO NSs was studied under different substrates (glass and silicon (Si)). The samples revealed that the synthesized ZnO NWs strongly depended on the thermal treatment time. Prepared samples were well characterized using ultraviolet visible (UV-Vis) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), and energy-dispersive X-ray (EDX) spectroscopy. The optical band gap (E_g) widened from 3.2 to 3.3 eV as the thermal treatment time increased and the transmittance of the NWs improved to approximately 75%, accompanied by a blue-shift at the UV absorption edge. FTIR results disclosed that ZnO absorption bands in the region between 445.5 and 478.3 cm^–1 have appeared from interatomic vibrations owing to the stretching of the Zn–O bond. XRD findings of the studied samples disclosed the polycrystalline hexagonal wurtzite structure with preferred orientation along the c-axis. According to the FESEM images, the morphological transition of the hierarchical ZnO NWs to individual NWs architectures was accomplished by increasing the treatment time from 0 to 3 h. Also, FESEM images indicated that the substrate type played a crucial role in determining the morphologies of 1D ZnO NSs. EDX outcomes showed a little Zn deficiency in the prepared samples with slightly different stoichiometric ratios between Zn and O atoms. Our current work could form the foundation for fabricating future nano-optoelectronic devices.