Date of Award
1992
Degree Type
Dissertation
Degree Name
Doctor of Philosophy
Abstract
Interactions of oxygen with Zr(0001) have been studied using low energy electron diffraction (LEED), work function ({dollar}\Delta\phi{dollar}), static and dynamic secondary ion mass spectrometry (SSIMS, DSIMS), thermal desorption spectroscopy (TDS), Auger electron spectroscopy (AES) and nuclear reaction analysis (NRA).;The initial sticking coefficient of oxygen is close to unity up to {dollar}\sim{dollar}0.75 ML at 90, 293 and 473 K. Oxygen chemisorption is disordered at room temperature and below, with some oxygen locating in on-top sites and some subsurface. Heating the disordered surface to {dollar}\sim{dollar}473 K causes all oxygen to move to subsurface sites and a (1 x 2) ordered oxygen underlayer is formed consisting of three rotated domains of (1 x 2) superstructure with the oxygen atoms located between the first and second planes of zirconium atoms. This structure is quite stable up to about 573 K, above which temperature oxygen diffuses into the bulk.;AES measurements employing oxide and metal signals were used to model the growth of oxide which was found to be temperature dependent: layer-by-layer at 90 K, island at 473 K, and layer-by-layer for the first 1-2 layers followed by island growth at room temperature. Both NRA and AES indicate linear oxygen uptake kinetics at 90 K with abrupt passivation as the limiting thickness is reached ({dollar}\sim{dollar}4 ML).;SSIMS ion yield data taken during the oxidation of Zr(0001) at 90, 293 and 473 K was interpretable in the context of the oxygen chemisorption behaviour, the oxide growth models and the depth sensitivity of SSIMS. The ion yields do not change in a simple manner with oxygen coverage.;Dissolution into the bulk of the saturated oxide layer grown at 90 K appears to occur by an island-type mechanism rather than layer-by-layer dissolution from the oxide-metal interface. Large {dollar}\Delta\phi{dollar} changes that occur upon oxidation at 90 K and subsequent temperature ramping of the saturated oxide to 300 K are attributable to reversible molecular oxygen adsorption on the oxide.;The diffusion of oxygen normal to the {dollar}\langle{dollar}0001{dollar}\rangle{dollar} plane of zirconium has been measured by AES: {dollar}D\sb0{dollar} = (4.14 {dollar}\pm{dollar} 1.92) {dollar}\times{dollar} 10{dollar}\sp{lcub}-2{rcub}{dollar} cm{dollar}\sp2{dollar} s{dollar}\sp{lcub}-1{rcub}{dollar} and {dollar}E\sb{lcub}\rm a{rcub}{dollar} = 199.1 {dollar}\pm{dollar} 2.6 kJ mol{dollar}\sp{lcub}-1{rcub}{dollar}. The fundamental vibrational frequency, {dollar}\nu{dollar}, for the {dollar}\alpha{dollar}-Zr lattice was calculated to be (6.3 {dollar}\pm{dollar} 2.9) {dollar}\times{dollar} 10{dollar}\sp{lcub}13{rcub}{dollar} s{dollar}\sp{lcub}-1{rcub}{dollar}.
Recommended Citation
Flinn, Bernard Jerome, "Interactions Of Oxygen With Zirconium(0001)" (1992). Digitized Theses. 2175.
https://ir.lib.uwo.ca/digitizedtheses/2175