Effects of Substrate Temperature and Sputtering Power on the Optical and Electrical Properties of Al-doped Zinc Oxide Thin Films by Reactive RF Magnetron Sputtering

Al doped zinc oxide (AZO) thin films were deposited on glass substrates with radio frequency (RF) magnetron sputtering. The influence of substrate temperature (Ts) and RF power (Pw) on the structural, optical and electrical properties of the AZO films were investigated. The X-ray diffraction patterns show that AZO films deposited over 100 degrees C have hexagonal-wurtzite phase structures with highly c-axis preferred orientations, and the average crystal size increases upon the promotion of the Ts. When the Ts increases from room temperature (RT) to 250 degrees C, the transmittance and the optical band gap of the AZO films increase slightly, whereas the resistivity decreases. The sputtering power also has a strong effect on the resistivity. As the sputtering power increases from 70 to 140W, the resistivity firstly decreases to the minimum at the power of 110W, and then it increases. It is also found that annealing is an effective way to decrease the resistivity of the AZO thin films (Ts=250 degrees C and Pw=110W) from similar to 2x10-1 to similar to 3x10-3 Omega.cm.