Effects of sputtering power on the properties of Al-doped ZnO films deposited on amorphous silicon films substrate

Al-doped ZnO (AZO) transparent conducting films were prepared on amorphous silicon (a-Si) films with various sputtering powers by radio frequency (RF) magnetron sputtering at room temperature. The effects of the sputtering power on the properties of AZO films deposited on a-Si films substrate and substrate itself were investigated. The microstructures, electrical and optical properties of AZO films were systematically analyzed by surface profiler, X-ray diffractometry, scanning electron microscope, four-point probe measurement and UV/vis spectrophotometer. The XRD patterns and SEM pictures indicate that the crystallinity of AZO thin films was markedly improved with sputtering power up to 1000 W, but worsened above this value. However, the cross-sectional SEM images indicate that a-Si films were obviously bombarded under different sputtering powers, and its thickness was reduced from 2.8% to 29.2% with increasing sputtering power from 300 W to 1200 W. The lowest resistivity of 2.25 × 10−3 Ω cm was obtained at 1000 W. The results demonstrate that AZO films deposited on a-Si films are suitable for application in heterojunction (HJ) solar cells as transparent conductive electrode layers.