Plasma modification of transition metal nitride/oxynitride (MOxNy) surfaces for enhanced surface properties is highly desirable, given the scalability of such methods and limitations of thermal treatments. In situ x-ray excited photoelectron spectroscopy demonstrates that the O 2 plasma oxidation of VOxNy films generates non-lattice N1s surface features with binding energies near 396.5 eV, which are associated with the nitrogen reduction reaction activity but not observed upon thermal oxidation. The NH 3 plasma generates N1s surface features near 400.5 eV binding energy. The O 2 +NH 3 plasma generates both types of N1s features. Annealing in UHV to <1000 K reverses plasma-induced changes to N1s spectra. Density functional theory (DFT) calculations integrated with the experiments indicate that the plasma-induced N1s features at ∼396.5 eV and 400.5 eV are V≡≡N: and V− −NH 2 sites, respectively, with significantly lower thermal stabilities than lattice N sites. These results provide practical insight regarding the plasma modification of MOxNy surfaces for important applications.
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