The effects of surface morphology on optical and electrical properties of nanostructured AZO thin films: Fractal and phase imaging analysis

Abstract

Highly transparent aluminum-doped ZnO (AZO) thin films were prepared by using sol–gel dip coating (SGDC) technique. The effects of Al dopant concentrations on the electrical, optical and structural properties of the AZO films were studied comprehensively. XRD results showed that all the prepared AZO films were polycrystalline and had the hexagonal wurtzite structure. As it is indicated by AFM analysis results, the enhancement of the both surface smoothness and autosimilarity of the films with increasing Al incorporation makes them suitable for optoelectronic applications. The negative surface skewness of pure and 1 at.% AZO thin films indicate porous morphology and low kurtosis while the positive skewness and higher kurtosis value of the 3 at.% sample make it favorable for nanotribological applications. The AFM phase contrast images of AZO thin films revealed the segregation of Al dopant in the grain boundaries. The optical transparency and electrical conductivity of samples enhanced with Al doping and the 1 at.% AZO thin films have the best electrical conductivity with average transmittance of 88.5% in visible region. The optical characteristics such as light absorbing and refractive index were studied based on fractal feature of AZO thin films.