CHEMICAL-REACTIONS OF N2+ ION-BEAMS WITH 1ST-ROW TRANSITION-METALS

Ion beam studies of chemical reactions between nitrogen and surfaces of the first-row transition metals are reported. X-ray photoelectron spectroscopy (XPS) and thermal desorption mass spectrometry under ultra-high vacuum conditions are used to examine the products induced by 30-3000-eV N2+ beams on the polycrystalline metal foils. The reaction results in the formation of metal nitrides which are similar to the pure metal nitride compounds. The amount of nitrogen reacting with the metal can be correlated to the enthalpy of formation of the metal nitride. Estimates of the thickness of the reacted layer are obtained from LSS projected ion range calculations. The chemical nature of the reaction is supported by identification of the products through energy level shifts and by the agreement with thermodynamic predictions. A mechanism is proposed for the reaction which involves charge exchange neutralization and dissociation of the ion at the surface followed by penetration into the lattice, thermalization, and finally chemical reaction. © 1979 American Chemical Society.