1983 年 24 巻 8 号 p. 574-580
ESCA data have been obtained on the incorporation of oxygen into nickel surfaces at room temperature. The surfaces were cleaned by argon ion bombardment, and the Ni 2p 3/2 line was observed as a function of the exposure to oxygen. The development of NiO-like components indicated that oxygen was being incorporated into the surface lattice. At low oxygen exposures a linear kinetic law was observed, with W=1.65×10−3L+0.226, where W is the thickness of the incorporated layer in nm and the exposure, L, is tp1⁄2, t being the exposure time in seconds and p the oxygen pressure in Pa. At high exposures, which were defined approximately as L>250, the thickness followed the logarithmic tarnishing law, with W=1.44×10−2lnL+0.533. We have postulated that the initial stage involves the incorporation of oxygen into the surface lattice via a cooperative displacement of the surface nickel atoms by a process of thermal activation assisted by a surface electric field induced by a charge transfer from a chemisorbed layer. The second stage appears to require the diffusion of oxygen into the bulk by means of thermal activation assisted by a strong electric field across the oxidized layer maintained by electron tunneling from the valence band of the bulk nickel.
