Appearance potential spectroscopy study of the oxidation of CoNi alloy surfaces

Soft X-ray appearance potential spectroscopy was used to study the composition and electronic structure of the solid surface of CoNi alloys (20-80% Ni), giving mainly density of vacant states above the Fermi level, and the electron binding energy of atoms. AES was also used for the chemical state and composition of the surface. The content of Ni is higher by several percent in the surface layers and reaches an equilibrium value after prolonged heating. Oxidation increases the binding energies of both Ni and Co in the alloy and also the pure state, by 0.6 to 1.8 eV, and the binding energy of Ni in the alloy is higher than that in the pure state by 0.8 eV, and for Co it is lower by 0.4 eV. 9 ref.--R.D.P.