Preparation and characterization of fast ion conducting lithium thio-germanate thin films grown by RF magnetron sputtering

In this study, amorphous lithium thio-germanate thin films were prepared by radio frequency (RF) sputtering deposition in Ar atmospheres. For the first time, new high quality lithium germanium sulfide nLi₂S GeS ₂ thin films, n = 1, 2, and 3, have been successfully made by RF sputtering and synthesized as new solid state electrolytes. Although these materials are unstable in air, the starting materials, target materials, and thin films made from them were thoroughly characterized by x-ray diffraction (XRD), Raman spectroscopy, SEM, x-ray photoelectron spectroscopy (XPS), and impedance spectroscopy using special setups to prevent contamination. These high quality thin films did not show any cracks and pits on the surface and the ionic conductivities of the thin films are 2-3 orders of magnitude higher than reported values for similar lithium containing oxide thin films. In this way, this work may provide a new way for developing new thin-film electrolytes for solid state lithium ion batteries.