Effect of the base pressure achieved prior deposition on the main properties of ZnO:Al films obtained by DC magnetron sputtering at room temperature for electrical contact use

The effect that the base pressure achieved prior to deposition has upon the electrical, optical, structural, and chemical properties of ZnO:Al [aluminum-zinc oxide (AZO)] thin films was studied. The thin films were obtained at room temperature on glass substrates by direct-current magnetron sputtering with a power of 120 W (corresponding to a power density of 2.63 W/cm2) and a total deposition pressure of 4.0 mTorr (0.53 Pa) with only argon gas. It was observed that all AZO characteristics and properties varied with base pressure without following a simple tendency, although some correlation was found between the crystallinity and deposition rate, with the latter depending directly upon the achieved base pressure. However, three distinct vacuum zones were identified, each of which produced AZO thin films that exhibited similar characteristics and properties. Among the base pressures studied, the lower base pressure zone [best vacuum level: under ∼5.7 × 10−7 Torr (∼7.6 × 10−5 Pa); dark yellow zone] produce...