Field-Induced and Surface-Catalyzed Formation of N2H Ions

Using H₂-N₂ mixed gases, high-electric-field-induced formation of ions such as N₂ ⁺ and N₂H⁺ on a surface of gold has been investigated in the pulsed-laser time-of-flight atom-probe field ion microscope. The N₂H⁺ ions are found from the lattice steps of the surface in the range (30-40) V/nm. The formation of the ions depends not only on the applied field strength, but also on the atomic structure of the substrate. By applying theoretical values of the binding energy and ionization potentials of N₂H, as calculated by the ab initio method and using measurements of the energy distributions of the N₂ ⁺ and N₂H⁺ ions, several conclusions can be drawn.