The chemical stability of phosphate glasses can be improved through the incorporation of nitrogen into the structure. In nit rided amorphous Li3PO4 thin films (LiPON), the exceptional stability and enhanced Li+ conductivity make them particularly attractive for microbattery applications. Reported here are Li-7, P-31, and N-15 solid-state nuclear magnetic resonance (NMR) studies of LiPON thin films fabricated by an ion beam-assisted deposition (IBAD) process. Variable temperature measurements of the Li-7 resonance yield an activation energy of about 0.2 eV, which is smaller than values obtained from ionic conductivities. P-31 spectra provide direct evidence for at least three phosphate environments: two resonances associated with PO24- and PO43-structures and a third anomalous peak assigned to a nitrided tetrahedral phosphate structural unit of charge -3. Additional evidence exists for other nitrided phosphate structures of charge -2. N-15 spectra show evidence for P-N=P type units and molecular N-2 with relative intensities that vary with the nitrogen ion beam gun voltage. No N-15 peak associated with trigonal NP3 units is observed. Additional evidence for molecular N-2 is provided by Fourier transform infrared measurements. A structural model of the phosphorus oxynitride host is presented. (c) 2005 The Electrochemical Society. [DOI: 10.1149/1.1856922] All rights reserved.