Temperature-tuned optical bandgap of Al-doped ZnO spin coated nanostructured thin films

Abstract

Al-doped ZnO (AZO) nanostructured thin films were produced by spin coating of AZO ink. The structural characteristics were determined by x-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. XRD plot showed well-defined and intensive diffraction peaks belonging to hexagonal crystal structure. AZO thin films were observed in the form of nanostructure with size varying generally between 20 and 30 nm in the SEM image. The room temperature bandgap energies of undoped and Al-doped ZnO nanostructured films were obtained as 3.32(7) and 3.35(3) eV, respectively. Temperature-tuned bandgap energy characteristics of AZO films were revealed applying transmission experiments by varying the sample temperature. The temperature-bandgap energy dependency was studied by Varshni and Bose-Einstein expressions and optical parameters of AZO films were revealed.