Functional properties of transparent Al, Mg-doped and Al-Mg co-doped ZnO nanostructures grown by electrochemical and chemical bath deposition: a comparative study

Undoped (ZnO), Al, Mg-doped (AZO, MZO), and Al–Mg co-doped ZnO (AZMO) nanostructures with different concentrations ratios of Al/Mg were deposited on conductive FTO substrate via two methods of deposition in solution: electrodeposition (ED) and chemical bath deposition (CBD). The effect of varied amounts of Al/Mg was characterized via electrochemical, Mott–Schottky (M-S), field-emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), and optical transmittance techniques. Experimental results revealed that, M–S plots of conductivity n-type were observed for all samples. An increase in the density of the charge carriers (N D ) from 10 19 to 10 20 cm −3 , is clearly observed with the amounts of Al/Mg for both deposition methods. According to the FE-SEM observations, when the amount of Al/Mg is increased in the solution, the grains size decreases. AFM morphological analysis indicated that the surface morphology and the roughness were significantly influenced by the amounts of Al/Mg and the elaboration process. XRD patterns revealed that all nanostructures of deposits have a hexagonal wurtzite structure and polycrystalline nature with a (002) and (100) preferential orientation for ED and CBD, respectively. The values of crystallite size were 29 and 27 nm for the ZnO nanostructures synthesized via electrodeposition and chemical bath deposition, respectively. Interestingly, for both doped and co-doped samples; the values were small indicating poor crystallization. From optical measurements, band gaps obtained for ZnO nanostructures deposited by ED and CBD are 3.28 and 3.20 eV, respectively. In addition, an increase in the visible transmission and optical gap of doped nanostructures was observed for both processes (> 89 %), suggesting larger prospects for its use in optoelectronic devices.