Fabrication and properties evaluation of aluminum and ruthenium co-doped zinc oxide thin films

Aluminum and ruthenium co-doped zinc oxide transparent conducting thin films were grown on polyethylene terephthalate substrate at 20 °C by RF magnetron sputtering method. The structural and physical properties of the films were investigated with respect to variation of discharge power density. The XRD and FESEM results show that the film with 3.6 W/cm2 power density has the best crystallinity and larger pyramid-like grains, therefore the resistivity reached to lowest value of 8.6 × 10−4 Ω cm. The low carrier mobilities of the films (3.6–8.9 cm2 V−1 s−1) not only were limited by ionized impurity scattering since the carrier concentrations were ranged from 2.0 × 1020 to 8.2 × 1020 cm−3, but chemisorption of oxygen on the film surface and grain boundary has to be taken into account. The transmittances of the films in the visible range are greater than 80%, while the optical band gaps are in the order of 3.337–3.382 eV.