Influence of doping behavior of Al on nanostructure, morphology and optoelectronic properties of Al Doped ZnO thin film grown on FTO substrate

Al doped ZnO nanostructures deposited on FTO glass substrate by spray pyrolysis method with different Al doping levels (0-5 wt%). The structural, morphological, optical and electrical properties of fabricated samples were analyzed using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), photoluminescence (PL), four point probe, and UV-Vis spectroscopy. The results obtained from XRD analysis indicated that the growth preferred orientation of the ZnO thin films strongly depend on Al doping value. Also the crystalline plane distance and grain size decreased while free electron density and energy band gap enhanced as the Al doping value increased. PL analysis revealed the Near Band emission in PL spectra shifts to shorter wavelengths and Fermi surface shifts to conduction band with increasing the Al content. Electrical measurements illustrated that the resistivity reduces with doping Al into ZnO and reaches to minimum value for 3 % Al doped sample. Also the surface morphology and surface roughness of samples deposited by various Al doping values studied by FESEM and AFM analyzes.