Ionic conductivity of bias sputtered lithium phosphorus oxy-nitride thin films

This manuscript reports a study of the ionic conductivity of radiofrequency sputter deposited, lithium phosphorous oxy-nitride (LIPON), solid state electrolyte amorphous thin films. Films having compositions near Li2.5PO3.5N0.5 were deposited under varying conditions of process gas, substrate bias, and deposition temperature. To understand the variations in ionic conductivity observed, the films were extensively characterized to examine structural and compositional differences, including examination by x-ray photoelectron spectroscopy (XPS), inductively coupled plasma–optical emission spectroscopy, and spectroscopic ellipsometry. For the XPS study, depth profiling was used to allow a critical examination of the role of triply coordinated nitrogen in the ionic conductivity of LIPON. The highest ionic conductivity of 9.8×10−6S/cm was obtained at an elevated deposition temperature and is correlated to a reduced density of defects, as indicated from the optical characterization. •The XPS depth profile study shows triply coordinated nitrogen does not correlate to ionic conduction.•This contradicts prior XPS studies but supports the solid state NMR results of Stallworth et al.•The ionic conduction of amorphous solid state electrolytes can be related to optical penetration depth.•A maximum ionic conductivity of 9.8 x 10-6 S/cm is observed.