Effect of post-annealing on structural and electrochemical properties of lithium phosphorus oxynitride thin film

Abstract In this study, the structural and electrochemical properties of post-annealed lithium phosphorus oxynitride (LiPON) thin films were confirmed. LiPON thin films were deposited using a radio-frequency sputtering method, and post-annealing was performed in the temperature range of 100–400 °C. Compared with the initial as-depo state, the impedance decreased at temperatures of 100 and 200 °C, and it again increased at 300 and 400 °C. As a result, the lowest impedance was seen at 200 °C, and it increased significantly at 400 °C. To verify the cause of the electrochemical changes, the structural properties of the post-annealed LiPON thin films were confirmed using analytical methods, including X-ray diffraction (XRD), scanning electron microscope (SEM), and X-ray photoelectron spectroscopy (XPS). XRD and SEM analysis showed that the LiPON thin film prepared in this study had a typical amorphous structure and no change in crystal structure and morphology occurred at 400 °C. XPS analysis showed that the Li1s/P2p ratio had the greatest effect on the impedance change, according to the post-annealing temperature of LiPON thin films. The ionic conductivity evaluation of the five samples showed that 200 °C post-annealing was effective in increasing the ionic conductivity of LiPON thin films, and the effect was reproducible.