Studies on surface chemical states of some metals and ceramics bombarded with energetic light-ions

An electron spectroscopy was applied to the investigation of surface chemical state of some metals and ceramics bombarded with energetic light ions. Bombardments of keV-order hydrogen ions on Sc, Ti, V, Y, Zr and Nb induced the XPS core-line chemical shifts to higher binding-energies by 0.2 - 1.4 eV, the appearence of new photopeaks at 3.0 - 5.0 eV below the Fermi level. Although the peak energies are lower by 1 - 3 eV than those calculated for MeH2 (Me = metal) by molecular-orbital theory, the peaks are assigned to the metal-H bonds. The chemical shifts induced by bombarding hydrogen-ions were also observed in the X-ray-induced Auger electron spectra (XAES) For Y, Zr and Nb. The hydride layers produced by the ion-implantation are more stable at high temperature than those obtained by thermal synthesis, because of the surface damages which prevent thermal diffusion of hydrogen. In the case of hydrogen-ion bombarded SiC, carbon enriched layer was observed in the near surface region, while the surfaces of Si3N4 and SiO2 became silicon-rich after the bombardments. On the other hand, the bombardments of H2+, D2+ and He+-ions on TiC, TiN and TiO2 made their surfaces titanium-rich. At high fluences, the X/Ti (X = C, N, O) become constant. The energy dependences of the steady state values of the C/Ti ratios have maximum at 2 - 4 keV/atom of incident ion, while those of the N/Ti and O/Ti ratios decreased with the increase in the ion energies. Incident-energy dependences of the Ti+/X+ ratios determined by SIMS substantiate that the sputtering is responsible for the surface compositional change of the binary compounds. The surface of TiO2 was easily reduced to Ti2O3 by the H2+ and D2+, or to TiO by the He+ and Ar+-ion bombardments. The difference in the reduced species is correlated with the thermodynamical parameters of the corresponding reduction reactions. (J.P.N.)