Characterization of polycrystalline tungsten surfaces irradiated with nitrogen ions by X-ray photoelectron spectroscopy

olycrystalline tungsten surfaces were irradiated at room temperature with two kinds of nitrogen ions N+ and N2+̶ at 2.5 keV by using an ion beam apparatus. Results of X-ray photoelectron spectroscopy (XPS) experiments performed using synchrotron radiation at SPring-8 showed that upon irradiation of the tungsten sample with either kind of ion, the full widths at half maximum (FWHM) of the W 4f7/2 and W 4f5/2 peaks broadened and the peaks at 35.8 eV and 37.8 eV which correspond to WO3 binding energies increased slightly; this indicated the formation of tungsten nitride at the subsurface below the interface