Dependences of the Al thickness and annealing temperature on the structural, optical and electrical properties in ZnO/Al multilayers

High-quality (0001) oriented ZnO (300 Å) film and [ZnO(100 Å)/Al(tAl)]3 (tAl = 0.6, 1.7, 2.8 Å) multilayers have been established at room temperature on Al2O3 (0001) substrates by ion-beam sputtering. The structural, optical and electrical properties of multilayers as functions of both the Al thickness and annealing temperature are reported. We have verified that Al thickness and annealing temperature are the key factors to optimize transparency-conducting property in ZnO/Al multilayers. The optimum Al thickness and annealing temperature for ZnO/Al multilayer of 300 Å thin is 1.7 Å (about one Al atomic layer) and 400 °C, respectively, leading to the relatively lower resistivity (2.8 × 10− 3 Ω cm) and higher Hall mobility (10 cm2/V·s) without suppression of the visible transmittance (above 85%).