About cookies on this site Our websites require some cookies to function properly (required). In addition, other cookies may be used with your consent to analyze site usage, improve the user experience and for advertising. For more information, please review your options. By visiting our website, you agree to our processing of information as described in IBM’sprivacy statement. To provide a smooth navigation, your cookie preferences will be shared across the IBM web domains listed here.
Publication
Physical Review B
Paper
Growth of Ce-Nb oxide films: A test of oxidation theory
Abstract
Experiments on the oxidation, at room temperature, in 5×10-8 Torr oxygen, of vapor deposited films of cerium, niobium, and niobium covered by some monolayers of cerium are reported. The valence-band structure was studied by ultraviolet photoemission spectroscopy (UPS), the surface potential due to chemisorbed oxygen was measured by measuring work-function change by UPS, and oxide growth was followed by x-ray photoelectron spectroscopy. The energy level a of oxygen chemisorbed on CeO2 was determined from UPS difference spectra and found to be at 4 eV below the Fermi level F. Comparing this with measured values of the surface potential (VS=-0.6 V) we conclude that contrary to earlier predictions, the entire value of the Mott potential VMe-1(F-a) does not materialize as a surface potential in the course of oxidation. We found, that for the oxidation of Nb the incorporation of oxygen ions at the surface is the rate-limiting step, while in case of cerium, and niobium covered by some monolayers of cerium, the first stage of oxidation is limited by oxygen-ion diffusion, and the second stage of oxidation is limited by electron tunneling. © 1985 The American Physical Society.