Transparent and conductive aluminum doped zinc oxide films prepared by mid-frequency reactive magnetron sputtering

In this study, aluminum doped zinc oxide films were prepared by reactive mid-frequency (MF) magnetron sputtering (Leybold TwinMag(TM)) at deposition rate of approx. 9 nm/s and substrate temperature of 100 to 300 degrees C. Process stabilization in the metallic mode was performed by the control of plasma impedance due to adjustment of oxygen flow. Metallic Zn:Al targets with different aluminum content were used. ZnO:Al films prepared by this technique exhibit resistivity of 3.0 x 10(-4) Omega cm at 200 degrees C substrate temperature and 4.8 x 10(-4) Omega cm at 100 degrees C, respectively, for films of approx. 500 nm thickness. The optical, electrical and structural properties of these films were investigated by means of optical spectroscopy (UV-VIS-NIR), X-ray diffraction, atomic force microscopy, Hall mobility and conductivity measurements. Electron probe micro analysis and secondary ion mass spectroscopy were used for chemical characterization.