A microwave-assisted solvothermal process to synthesize Al-doped ZnO powders and its optical and electrical properties

Aluminum-doped ZnO (AZO) nanoparticles with different Al doping levels were synthesized using a microwave-assisted method. The synthesized AZO crystal structure and shape were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD results show that the produced nanoparticles can be fully assigned to the hexagonal wurtzite ZnO crystalline structure. SEM results showed that the morphologies of the AZO samples were spherical-like structure, and the crystalline size of the samples decreased with the increasing Al doping levels. The doping level of the synthesized nanoparticles were analyzed by Energy Dispersive X-ray Detector (EDX), and the result showed that Al element was successfully incorporated into ZnO crystal lattice. The optical properties and electrical properties of AZO samples were researched by UV-Vis spectroscopy and four-point probe, respectively. The optical spectra show that the band of the samples are affected by Al doping levels. The resistivity of the AZO samples first decreased and then increased with increasing the Al doping content due to the changes in the electron and dopant concentrations. AZO exhibited the smallest electrical resistivity with Al doping content at 3.0 at.%,