Effect of aging under ambient conditions on the optical properties of Al-doped ZnO thin films deposited by direct current sputtering

Transparent and conductive Al-doped ZnO (AZO) thin films were deposited on a glass substrate by direct current sputtering. In a previous study, we noted the influence of time on structural and electrical characteristics of films. In the present paper, the effect of a two-year aging under ambient conditions on the optical properties was investigated. A global improvement of the optical properties of AZO thin films was observed. The optical transmittance spectra revealed a high transmittance more than 90% in the Vis-NIR regions and a high absorption in the ultraviolet range. It is assumed that the crystallinity segregation leads to the decrease of optical scattering. The results from the optical measurements showed a reorganization of the structure leading to the degradation of the structural homogeneity. Nevertheless, the evolution of the figure of merit shows that Al-doped ZnO is a good candidate for the manufacturing and the commercialization of transparent conducting oxide devices.