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Water Adsorption on ZnO(0001): Transition from Triangular Surface Structures to a Disordered Hydroxyl Terminated phase
KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Materialfysik, MF.
KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Materialfysik, MF.
KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik.
KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Materialfysik, MF.ORCID-id: 0000-0002-9663-7705
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2010 (Engelska)Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 114, nr 25, s. 11157-11161Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

We present room temperature scanning tunneling microscopy and photoemission spectroscopy studies of water adsorption on the Zn-terminated ZnO(0001) surface. Data indicates that the initial adsorption is dissociative leaving hydroxyl groups on the surface. At low water coverage, the adsorption occurs next to the oxygen-terminated step edges, where water is believed to bind to zinc cations leaving off hydrogen atoms to under-coordinated oxygen anions. When increasing the water dose, triangular terraces grow in size and pits diminish until the surface is covered with wide irregular terraces and a large number of small pits. Higher water exposure (20 Langmuir) results in a much more irregular surface. Hydrogen, which is produced in the dissociation reaction is believed to have an important role in the changed surface structure at high exposures. The fact that adsorbed water completely changes the structure of ZnO(0001) is an important finding toward the understanding of this surface at atmospheric conditions.

Ort, förlag, år, upplaga, sidor
2010. Vol. 114, nr 25, s. 11157-11161
Nationell ämneskategori
Fysikalisk kemi
Identifikatorer
URN: urn:nbn:se:kth:diva-27268DOI: 10.1021/jp1004677ISI: 000278982300022Scopus ID: 2-s2.0-77954066762OAI: oai:DiVA.org:kth-27268DiVA, id: diva2:378720
Anmärkning
QC 20101216Tillgänglig från: 2010-12-16 Skapad: 2010-12-09 Senast uppdaterad: 2017-12-11Bibliografiskt granskad
Ingår i avhandling
1. Surface Reactivity and Electronic Structure of Metal Oxides
Öppna denna publikation i ny flik eller fönster >>Surface Reactivity and Electronic Structure of Metal Oxides
2011 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

The foci of this thesis are the metal oxides Cu2O, ZnO and Fe3O4 and their interaction with water and sulfur dioxide (SO2). The intention is to study SO2-induced atmospheric corrosion on a molecular level. All studies are based on photoelectron spectroscopy (PES) and scanning tunneling microscopy (STM) measurements. The band structure of Cu2O in the Γ-M direction has been probed by angle-resolved PES (ARPES). It reveals a more detailed picture of the bulk band structure than earlier data and gives the first experimental evidence of a dispersive hybridized Cu 3d-Cu 4s state. The experimental data is compared to band structure calculations. The structure of clean metal oxide surfaces and impact of sample preparation have been studied. Oxygen vacancies can form a (√3x√3)R30° reconstruction on Cu2O(111). Oxygen atoms adjacent to copper vacancies, steps or kinks are shown to be adsorption sites for both water and SO2. Annealing temperature influences the defect density and hydrogen content in ZnO, which can have large impact on the surface properties of ZnO(0001). Water is shown to adsorb dissociatively on ZnO(0001) and partly dissociatively on Cu2O(111). The dissociation occurs at undercoordinated oxygen sites on both surfaces. Water stays adsorbed on ZnO(0001) at room temperature but on Cu2O(111), all water has desorbed at 210 K. SO2 interacts with one or two undercoordinated O-sites on all studied oxide surfaces forming SO3 or SO4 species respectively. SO4 on Fe3O4(100) follows the (√2x√2)R45° reconstruction. On Cu2O(111) and ZnO(0001), SO2 adsorbs on defect sites. An SO3 to SO4 transition is observed on Cu2O(111) when heating an SO3 adsorbate layer from 150 K to 280K. Coadsorption of water and SO2 on ZnO(0001) and Fe3O4(100) has been studied briefly. Water blocks SO2 adsorption sites on ZnO(0001). On Fe3O4(100) and on one type of reduced ZnO(0001) sample, SO2 dissociation to atomic sulfur or sulfide occurs to a higher extent on water exposed surfaces than on clean surfaces. Water thus appears to increase the charge density on some surfaces. Further studies are needed to reveal the cause of this unexpected effect.

Ort, förlag, år, upplaga, sidor
Stockholm: KTH Royal Institute of Technology, 2011. s. xiv, 58
Serie
Trita-ICT/MAP AVH, ISSN 1653-7610 ; 2011:07
Nyckelord
oxides, surfaces, defects, cuprous oxide, zinc oxide, magnetite, water, OH, sulfur dioxide, photoelectron spectroscopy, scanning tunneling microscopy
Nationell ämneskategori
Övrig annan teknik
Identifikatorer
urn:nbn:se:kth:diva-33667 (URN)978-91-7415-995-0 (ISBN)
Disputation
2011-05-30, Electrum, C2, Isafjordsgatan 26, Kista, 10:00 (Engelska)
Opponent
Handledare
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QC 20110516

Tillgänglig från: 2011-05-16 Skapad: 2011-05-13 Senast uppdaterad: 2012-10-30Bibliografiskt granskad

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Yu, ShunKarlsson, Ulf O.

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Önsten, AnneliStoltz, DunjaPalmgren, PålYu, ShunGöthelid, MatsKarlsson, Ulf O.
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Materialfysik, MFMaterialfysik
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