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Önsten, A., Weissenrieder, J., Stoltz, D., Yu, S., Göthelid, M. & Karlsson, U. O. (2013). Role of defects in surface chemistry on Cu2O(111). The Journal of Physical Chemistry C, 117(38), 19357-19364
Open this publication in new window or tab >>Role of defects in surface chemistry on Cu2O(111)
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2013 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, no 38, p. 19357-19364Article in journal (Refereed) Published
Abstract [en]

High-resolution photoemission spectroscopy and scanning tunneling microscopy (STM) have been used to investigate defects on Cu2O(111) and their interaction with water and sulfur dioxide (SO2). Two types of point defects, i.e., oxygen and copper vacancies, are identified. Copper vacancies are believed to be the most important defects in both water and SO2 surface chemistry. Multiply coordinatively unsaturated oxygen anions (OMCUS) such as oxygen anions adjacent to copper vacancies are believed to be adsorption sites for both water and SO2 reaction products. Water adsorption at 150 K results in both molecular and dissociated water. Molecular water leaves the surface at 180 K. At 300 K and even more at 150 K, SO2 interacts with oxygen sites at the surface forming SO 3 species. However, thermal treatment up to 280 K of Cu 2O(111)/SO2 prepared at 150 K renders only SO4 on the surface.

Keywords
Be adsorption, Co-ordinatively unsaturated, Dissociated waters, High-resolution photoemission spectroscopy, Molecular water, Oxygen anion, Oxygen site, Water adsorption
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-133251 (URN)10.1021/jp3112217 (DOI)000330162500012 ()2-s2.0-84885032661 (Scopus ID)
External cooperation:
Funder
Swedish Research CouncilCarl Tryggers foundation Swedish Foundation for Strategic Research
Note

QC 20140224

Available from: 2013-10-30 Created: 2013-10-29 Last updated: 2017-12-06Bibliographically approved
Önsten, A., Stoltz, D., Palmgren, P., Yu, S., Claesson, T., Göthelid, M. & Karlsson, U. O. (2013). SO2 interaction with Zn(0001) and ZnO(0001) and the influence of water. Surface Science, 608, 31-43
Open this publication in new window or tab >>SO2 interaction with Zn(0001) and ZnO(0001) and the influence of water
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2013 (English)In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 608, p. 31-43Article in journal (Refereed) Published
Abstract [en]

Photoelectron spectroscopy has been used to study room temperature adsorption of sulfur dioxide on clean and water exposed (0001) surfaces of zinc and zinc oxide. Water has no significant effect either on clean or on SO2 exposed Zn(0001) at the low water pressures used (p < 10(-7) mbar). In the Case of the zinc-terminated ZnO(0001) surface, however, water adsorbs dissociatively and OH groups are shown to have a considerable effect on SO2 surface reactions. A strong oxidation reaction occurs between Zn(0001) and SO2 giving various sulfur containing species. On ZnO(0001), SO2 interacts mainly with oxygen sites giving SO3 or SO4 species. It is shown that the ZnO(0001) sample preparation procedure can have large effects on surface chemical and physical properties. Samples cleaned by four different preparation procedures are investigated, namely sputtering only and sputtering followed by annealing at 450 degrees C, 530 degrees C and 600-650 degrees C. Annealing at 600 degrees C leads to a transition from a partly OH-terminated surface to a triangularly structured surface free from OH groups. Adsorption of SO2 on the latter surface leads to a decreased surface conductivity, which hampers photoemission measurements. Water is shown to block SO2 adsorption sites on both 450 degrees C and 530 degrees C annealed samples. On the latter sample. SO2 reduction has been observed to a small extent on the clean surface and to a larger extent when the surface is prehydroxylated. Here, we speculate that water, similar to hydrogen, generates surface zinc clusters on ZnO(0001). Zinc clusters could enable charge transfer to the antibonding LUMO of the SO2 molecule and subsequent dissociation.

Keywords
Photoelectron spectroscopy, Zinc oxide, Sulfur dioxide, Water, Hydrogen, Defects, Sample preparation, Gas sensing
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-116720 (URN)10.1016/j.susc.2012.09.007 (DOI)000312615500005 ()2-s2.0-84870427475 (Scopus ID)
Funder
Swedish Research CouncilSwedish Foundation for Strategic Research
Note

QC 20130125

Available from: 2013-01-25 Created: 2013-01-25 Last updated: 2017-12-06Bibliographically approved
Yun, S. H., Lee, H.-S., Kwon, Y. H., Göthelid, M., Koo, S. M., Wågberg, L., . . . Linnros, J. (2012). Multifunctional silicon inspired by a wing of male Papilio ulysse. Applied Physics Letters, 100(3), 033109
Open this publication in new window or tab >>Multifunctional silicon inspired by a wing of male Papilio ulysse
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2012 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 100, no 3, p. 033109-Article in journal (Refereed) Published
Abstract [en]

Effective entrapment of air and light is a key element for maintaining stable superhydrophobicity and enhancing anti-reflection or absorption. Inspired by a wing of male Papilio ulysse having a unique structure for enabling effective trapping of air and light, we demonstrate that the structure consisting of well-defined multilayer decorated by nanostructures can be obtained on a silicon wafer by a simple microelectromechanical process, consequently resulted in stable superhydrophobocity under static and dynamic conditions, and strong wideband optical absorption.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2012
Keywords
SURFACES, ROUGHNESS
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-83068 (URN)10.1063/1.3664636 (DOI)000299386800047 ()2-s2.0-84863038865 (Scopus ID)
Note
QC 20120403Available from: 2012-04-19 Created: 2012-02-12 Last updated: 2017-12-07Bibliographically approved
Szamota-Leandersson, K., Leandersson, M., Göthelid, M. & Karlsson, U. O. (2011). Correlated development of a (2x2) reconstruction and acharge accumulation layer on the InAs(111)-Bi surface. Surface Science, 605(1-2), 12-17
Open this publication in new window or tab >>Correlated development of a (2x2) reconstruction and acharge accumulation layer on the InAs(111)-Bi surface
2011 (English)In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 605, no 1-2, p. 12-17Article in journal (Refereed) Published
Abstract [en]

We have studied the formation of a Bi induced (2x2) reconstruction on the InAs(111)Bsurface. In connection to the development of the (2x2) reconstruction, a two dimensionalcharge accumulation layer located in the bottom of the InAs conduction band appears as seenthrough a photoemission structure at the Fermi level. Not well ordered Bi layers do not inducea charge accumulation. The Bi induced reconstruction reduces the polarisation of the pristinesurface and changes the initial charge distribution. InAsBi alloying occurs below the surfacewhere Bi act as charge donor leading to the charge accumulation layer.

Keywords
Adatoms, Indium arsenide, Bismuth, Photoemission, 2 DEG
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-24468 (URN)10.1016/j.susc.2010.09.015 (DOI)000286021000003 ()2-s2.0-78649703757 (Scopus ID)
Funder
Swedish Research Council
Note
QC 20100910Available from: 2010-09-10 Created: 2010-09-10 Last updated: 2017-12-12Bibliographically approved
Karlsson, U. (2010). MAX IV : An ultrabrilliant synchrotron radiation facility. Paper presented at IVC-18/ICN+T 2010 Beijing.
Open this publication in new window or tab >>MAX IV : An ultrabrilliant synchrotron radiation facility
2010 (English)Conference paper, Published paper (Refereed)
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-82727 (URN)
Conference
IVC-18/ICN+T 2010 Beijing
Note
QC 20120214Available from: 2012-02-12 Created: 2012-02-12 Last updated: 2012-02-14Bibliographically approved
Önsten, A., Stoltz, D., Palmgren, P., Yu, S., Göthelid, M. & Karlsson, U. O. (2010). Water Adsorption on ZnO(0001): Transition from Triangular Surface Structures to a Disordered Hydroxyl Terminated phase. The Journal of Physical Chemistry C, 114(25), 11157-11161
Open this publication in new window or tab >>Water Adsorption on ZnO(0001): Transition from Triangular Surface Structures to a Disordered Hydroxyl Terminated phase
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2010 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 114, no 25, p. 11157-11161Article in journal (Refereed) 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.

National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-27268 (URN)10.1021/jp1004677 (DOI)000278982300022 ()2-s2.0-77954066762 (Scopus ID)
Note
QC 20101216Available from: 2010-12-16 Created: 2010-12-09 Last updated: 2017-12-11Bibliographically approved
Önsten, A., Göthelid, M. & Karlsson, U. O. (2009). Atomic structure of Cu2O(111). Surface Science, 603(2), 257-264
Open this publication in new window or tab >>Atomic structure of Cu2O(111)
2009 (English)In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 603, no 2, p. 257-264Article in journal (Refereed) Published
Abstract [en]

Low-energy electron diffraction and scanning tunneling microscopy have been used to probe the surface atomic structure Of Cu2O(111) after various sample preparations. Annealing in oxygen gives a stoichiometric (1 x 1) oxygen terminated surface and further annealing in ultra-high vacuum results in a clear (root 3 x root 3)R30 degrees reconstruction and surface faceting. Tunneling from filled states in the reconstructed surface reveals a hexagonal pattern of large protrusions, which show an internal structure. The reconstruction is believed to be due to one-third of a monolayer of ordered oxygen vacancies. At areas on the surface where the large features are missing, another smaller type of protrusions is visible, which is associated with the ideal (1 x 1) surface. The relative position of the two types of features gives two possible models of the (111) surface. In the first model, the (1 x 1) surface is the ideal bulk terminated surface and coordinatively unsaturated oxygen ions are missing in the reconstructed surface. The second model agrees with the first model with the exception that coordinatively unsaturated copper ions in the outmost copper layer are missing in both the (1 x 1) and the reconstructed surface. The latter model is supported by previous surface free energy calculations. Since the undercoordinated copper ions have been suggested to be the catalytic active sites Of Cu2O(111), the presence or absence of these cations could be of great importance for the fundamental understanding of the surface reactivity Of Cu2O and of copper-based catalysts.

Keywords
Catalysis, Copper oxides, Low-energy electron diffraction (LEED), Scanning tunneling microscopy, Scanning tunneling spectroscopies, Single crystal surfaces, Surface defects, Surface structure, scanning-tunneling-microscopy, energy synchrotron-radiation, temperature steam conversion, plasma-chemical preparation, density-functional theory, closed-shell interactions, electronic-structure, nanostructured catalysts, polar covalences, carbon-monoxide
Identifiers
urn:nbn:se:kth:diva-18173 (URN)10.1016/j.susc.2008.10.048 (DOI)000263384500003 ()2-s2.0-58249115242 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
Szamota-Leandersson, K., Leandersson, M., Palmgren, P., Göthelid, M. & Karlsson, U. O. (2009). Electronic structure of bismuth terminated InAs(100). Surface Science, 603(1), 190-196
Open this publication in new window or tab >>Electronic structure of bismuth terminated InAs(100)
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2009 (English)In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 603, no 1, p. 190-196Article in journal (Refereed) Published
Abstract [en]

Deposition of Bi onto (4 x 2)/c(8 x 2)-InAs(1 0 0) and subsequent annealing results in a (2 x 6) surface reconstruction as seen by low electron energy diffraction. The Bi condensation eliminates the original (4 x 2) Surface reconstruction and creates a new Structure including Bi-dimers. This Surface is metallic and hosts a charge accumulation layer seen through photoemission intensity near the Fermi level. The accumulation layer is located in the bulk region below the surface, but the intensity of the Fermi level structure is strongly dependent oil the Surface order.

Keywords
Adatoms, Indium arsenide, Bismuth, Photoemission, 2 DEG, Reconstruction, scanning-tunneling-microscopy, accumulation layer, surface, reconstructions, photoemission, inas, gas
Identifiers
urn:nbn:se:kth:diva-18136 (URN)10.1016/j.susc.2008.10.042 (DOI)000262828000032 ()
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
Karpus, V., Suchodolskis, A., Taulavicius, J., Karlsson, U. O., Assmus, W., Bruehne, S. & Uhrig, E. (2008). Photoemission spectroscopy study of si-ZnMgHo quasicrystals. Optical materials (Amsterdam), 30(5), 690-692
Open this publication in new window or tab >>Photoemission spectroscopy study of si-ZnMgHo quasicrystals
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2008 (English)In: Optical materials (Amsterdam), ISSN 0925-3467, E-ISSN 1873-1252, Vol. 30, no 5, p. 690-692Article in journal (Refereed) Published
Abstract [en]

The results of photoemission spectroscopy of the simple-icosahedral single-grain ZnMgHo quasicrystals are presented. Synchrotron radiation photoemission measurements were performed on in situ cleaved samples at 10(-10) mbar pressure and low, 160 K, temperature. The valence band photoemission spectra measured reveal a simple metal type valence band with a distinct Fermi edge and a sharp pseudogap feature, which originates from the van Hove singularities in the density of states. The photoemission spectra of the Mg 2p core level show the coordination shifts of Mg 2p, spin-orbit doublet due to inequivalent Mg sites in the quasicrystalline lattice.

Keywords
quasicrystals, pseudogap, photoemission spectroscopy
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-38348 (URN)10.1016/j.optmat.2007.02.011 (DOI)000252554800007 ()2-s2.0-37249014459 (Scopus ID)
Note
International Workshop on Advanced Spectroscopy and Optical Materials Location: Inst Expt Phys, Univ Gdansk, Gdansk, POLAND Date: JUN 11-14, 2006 Available from: 2011-08-25 Created: 2011-08-25 Last updated: 2017-12-08Bibliographically approved
Stoltz, D., Önsten, A., Karlsson, U. O. & Göthelid, M. (2008). Scanning tunneling microscopy of Fe- and O-sublattices on Fe3O4(100). Ultramicroscopy, 108(6), 540-544
Open this publication in new window or tab >>Scanning tunneling microscopy of Fe- and O-sublattices on Fe3O4(100)
2008 (English)In: Ultramicroscopy, ISSN 0304-3991, E-ISSN 1879-2723, Vol. 108, no 6, p. 540-544Article in journal (Refereed) Published
Abstract [en]

We present scanning tunneling microscopy of an octahedral (B) plane terminated (root 2 x root 2)R45 degrees-reconstructed surface of a natural magnetite (10 0) crystal. Implementing a W-tip we achieve the same resolution on Fe rows as was reported in the past either with the use of antiferromagnetic tips or on magnetite (Fe3O4) films. We show images of Fe or O sublattices of Fe3O4 with atomic resolution.

Keywords
scanning tunneling microscopy, magnetic oxides, surface structure, molecular-beam epitaxy, fe3o4(001) surface, electronic-structure, films, stm, reconstruction, photoemission, magnetite
National Category
Natural Sciences
Identifiers
urn:nbn:se:kth:diva-17566 (URN)10.1016/j.ultramic.2007.08.010 (DOI)000256209200006 ()2-s2.0-42049100124 (Scopus ID)
Note

QC 20100525

Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-7409-575X

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