Effects of crystallinity and impurities on the electrical conductivity of Li-La-Zr-O thin films

We present a study of the fabrication of thin films from a Li7La3Zr2O12 (LLZO) target using pulsed laser deposition. The effects of substrate temperatures and impurities on electrochemical properties of the films were investigated. The thin films of Li-La-Zr-O were deposited at room temperature and higher temperatures on a variety of substrates. Deposition above 600 °C resulted in a mixture of cubic and tetragonal phases of LLZO, as well as a La2Zr2O7 impurity, and resulted in aluminum enrichment at the surface when Al- containing substrates were used. Films deposited at 600 °C exhibited the highest room temperature conductivity, 1.61×10-6 S/cm. The chemical stability toward metallic lithium was also studied using X-ray photoelectron spectroscopy, which showed that the oxidation state of zirconium remained at +4 following physical contact with heated lithium metal.