Investigation on the Enhancement of the Thermoelectric Power Factor of ZnO Thin Films by Al-doping using Asymmetric Bipolar Pulsed-DC Magnetron Sputtering Technology

摘要

ZnO and Al-doped ZnO thin films were deposited on ceramic substrate by using an asymmetric bipolar pulsed-DC magnetron sputtering system under Ar atmosphere. Compacted ZnO powder and ZnO:Al2O3 premixed powder in copper supports were used as sputtering targets for the deposition of ZnO and Al-doped ZnO thin films, respectively. Optical emissions from the plasma during the deposition, measured using a high resolution spectrometer in the wavelength range of 360-800 nm, showed that the constituents of each target were successfully sputtered off. X-ray diffraction (XRD) analysis confirmed the formation of ZnO and Al-doped ZnO thin films of hexagonal crystal structure. The deposition rates of 24 and 15 nm/min were obtained for the ZnO and Al-dopoed ZnO thin films, respectively. The electrical conductivity and Seebeck coefficient of the thin films were measured at room temperature by the steady state and the Van der Pauw four probe methods, respectively. The increase in thermoelectric power factor of about 2 orders of magnitude was observed for the Al-doped ZnO thin films.