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Title Interaction of Water with Ordered Theta-Al₂0₃ Ultrathin Films grown on NiAl(100)
Creator/Author Ozensoy, Emrah ; Szanyi, Janos ; Peden, Charles HF.
Publication Date2005 Mar 03
OSTI IdentifierOSTI ID: 15016144
Report Number(s)PNNL-SA-44490
DOE Contract NumberAC05-76RL01830
Other Number(s)Other: 6694; KC0302010
Resource TypeJournal Article
Resource RelationJournal: Journal of Physical Chemistry B, 109(8):3431-3436
Research OrgPacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring OrgUSDOE
Related SubjectCrystal alpha-Al₂O₃(0001) surface; energy-loss-spectroscopy; vibrational properties; thin-films; Al₂O₃; adsorption; NiAl(001); H₂O; desorption; oxidation; Environmental Molecular Sciences Laboratory
Description/Abstract The structure of an ordered, ultra thin ⊖-Al₂0₃ film grown on a NiAl(100) single crystal surface was studied by Auger electron spectroscopy (AES), X-Ray photoelectron spectroscopy (XPS), and low energy electron diffraction (LEED), and its interaction with water was investigated with temperature programmed desorption (TPD), and XPS. Our results indicate that H₂O adsorption on the ⊖-Al₂0₃/NiAl(100) surface is predominantly molecular rather than dissociative. For ⊖H₂O< 1ML (ML=monolayer), H₂O molecules were found to populate Al³⁺ cation sites to form isolated H₂O species aligned in a row along the cation sites on the oxide surface with a repulsive interaction between them. For ⊖H₂O> 1ML, H₂O overlayers were observed to form three dimensional ice multilayers where water molecules start occupying both cationic and anionic adsorption sites on the oxide surface allowing the formation of hydrogen boding. A small extent of H₂O dissociation was observed to occur on the ⊖-Al₂0₃/NiAl(100) surface which was attributed to the presence of a low concentration of surface defects. Titration of these defect sites with absorbed H₂O molecules revealed an estimated defect density of ~0.-5 ML for the ⊖-Al₂0₃/NiAl(100) system consistent with the ordered nature of the synthesized oxide film.
Country of PublicationUnited States
LanguageEnglish
System Entry Date2008 Mar 24
Work Proposal No6694

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