Structural and compositional characterization of RF magnetron cosputtered lithium silicate films: From Li2Si2O5 to lithium-rich Li8SiO6

In this study, the structure and composition of lithium silicate thin films deposited by radio-frequency magnetron cosputtering are investigated. Five compositions ranging from Li2Si2O5 to Li8SiO6 were confirmed by inductively coupled plasma-optical emission spectroscopy, and structural analysis on the evolution of nonbridging oxygens in the thin films was conducted using Fourier transform infrared spectroscopy. It was found that nonbridging oxygens increased as the silicate network breaks apart with the increasing lithium content, which agrees with previous studies on lithium silicates. Thin film impurities were examined using x-ray photoelectron spectroscopy and time of flight secondary ion mass spectroscopy and traced back to target synthesis. This study utilizes a unique synthesis technique for lithium silicate thin films that can be used to model the lithium silicates formed on the surface of silicon anodes in lithium ion batteries and can bridge the understanding between this layer and the influence of silicates on ionic conductivity of the silicon interphase layer. (C) 2017 American Vacuum Society.