Effects of annealing temperature on structure and opt-electric properties of ion-conducting LLTO thin films prepared by RF magnetron sputtering

Highly transparent and ion-conducting lithium lanthanum titanate (LLTO) thin films were deposited on ITO/glass substrates by RF magnetron sputtering. The results of X-ray diffraction indicate that the as-prepared LLTO thin films and the annealed ones at temperatures up to 300 degrees C are amorphous; however, crystal phases, including La0.56Li0.33TiO3 and other unexpected ones, appear on the annealed films at 400 degrees C. SEM and AFM results show that the prepared films turn to be denser, smoother and more uniform up to 300 degrees C while the deteriorative results come out following the further enhancement of annealing temperature. Further characterization of opt-electric properties of the prepared films reveals that the annealed ones at 300 degrees C own the best optical transmittance of 85% and the highest room temperature ionic conductivity of 5.25 x 10(-5) S cm(-1), which are suitable for the application as an electrolyte of all-solid-state electrochromic devices. (C) 2010 Elsevier B.V. All rights reserved.