|Title||Non-equilibrium oxidation states of zirconium during early stages of metal oxidation|
|Publication Type||Journal Article|
|Year of Publication||2015|
|Authors||Ma, W, F. Herbert, W, Senanayake, SD, Yildiz, B|
|Journal||Applied Physics Letters|
The chemical state of Zr during the initial, self-limiting stage of oxidation on single crystal zirconium (0001), with oxide thickness on the order of 1 nm, was probed by synchrotron x-ray photoelectron spectroscopy. Quantitative analysis of the Zr 3d spectrum by the spectrum reconstruction method demonstrated the formation of Zr1+, Zr2+, and Zr3+ as non-equilibrium oxidation states, in addition to Zr4+ in the stoichiometric ZrO2. This finding resolves the long-debated question of whether it is possible to form any valence states between Zr-0 and Zr4+ at the metal-oxide interface. The presence of local strong electric fields and the minimization of interfacial energy are assessed and demonstrated as mechanisms that can drive the formation of these non-equilibrium valence states of Zr. (C) 2015 AIP Publishing LLC.