Investigation of ZnO:Al thin films sputtered at different deposition temperatures

ZnO:Al (AZO) thin films were prepared on glass substrates by using RF magnetron sputtering at various deposition temperature, and their properties were investigated. With increasing deposition temperature, the crystallinity was slightly improved, whereas the resistivity continuously deteriorated due to a decrease in the mobility and in the carrier concentration. From an X-ray photoelectron spectroscopy (XPS) analysis, the behaviors of the mobility and the carrier concentration were affected by impurity bonding such as oxygen species on the film surface. The mobility decreased due to an increase in the potential height and was the main factor at a low deposition temperature (200 °C). In addition, the carrier concentration decrease due to the trapping of electrons and to the reduction of oxygen vacancy and was dominant factor at a high deposition temperature (400 °C). For the deposition of AZO films, if improved electrical properties are to be obtained, the deposition temperature needs to choose so as to minimize the impurity bonding.