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Organic-metal interfaces, in particular, self-assembling systems, are interesting in the field of molecular electronics. In this study, we have investigated the formation of the Ag(110)-iron phthalocyanine (FePc) interface in a coverage... more
Organic-metal interfaces, in particular, self-assembling systems, are interesting in the field of molecular electronics. In this study, we have investigated the formation of the Ag(110)-iron phthalocyanine (FePc) interface in a coverage range of less than 1 and up to 2 ML using synchrotron based photoelectron spectroscopy and low energy electron diffraction. As-deposited FePc forms a densely packed first layer exhibiting a 3 x 2c(6 x 2) symmetry. Upon thermal treatment the order at the interface is modified depending on the initial FePc coverage, resulting in less densely packed but still ordered superstructures. The first monolayer is relatively strongly bound to the substrate, leading to the formation of an interface state just below the Fermi level. The highest occupied molecular orbital of FePc in the second layer is found at 1 eV higher binding energy compared to the interface state.
Research Interests: Engineering, Materials Science, Chemistry, Electronics, PHOTOELECTRON SPECTROSCOPY, and 15 moreChemical Physics, Medicine, Molecular Electronics, Band Structure, Silver, Physical sciences, Nanostructures, Iron, Low energy electron diffraction, Electron Density, CHEMICAL SCIENCES, Thermal Treatment, Interface States, Surface Properties, and Binding Energy
ABSTRACT We report a study on the spatial homogeneity and nitridation of a nanopattern template using a spectroscopic photoemission and low energy electron microscopy. The template was composed of Al nanodots which were patterned into a... more
ABSTRACT We report a study on the spatial homogeneity and nitridation of a nanopattern template using a spectroscopic photoemission and low energy electron microscopy. The template was composed of Al nanodots which were patterned into a SiO2/Si(1 1 1) surface using e-beam lithography and reactive ion etching. The template exhibited a global inhomogeneity in terms of the local topography, Al composition and structure of the individual nanopatterns. After nitridation, the individual nanopatterns were diminished, more corrugated and faceted. The nitridated nanopatterns were structurally ordered but differently orientated. The nitridation effectively removed the fluorine contaminants by decomposition of the fluorocarbon sidewalls, resulting in the AlN nanopatterns and partially nitridated Si substrate surface outside the nanopattern domains. (C) 2012 Elsevier B. V. All rights reserved.
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Research Interests: Engineering, Physics, Chemistry, Carbon, X ray absorption spectroscopy, and 13 moreChemical Physics, Medicine, Adsorption, Scanning tunneling microscopy, Iodine, Physical sciences, Platinum, CHEMICAL SCIENCES, Electrons, X Ray Photoelectron Spectroscopy, Monolayer, Organometallic Compounds, and Scanning Tunneling Microscope (STM)
The properties of a Sn-induced two-dimensional electron gas at the As-terminated InAs(111)B(1×1) surface was studied by synchrotron radiation photoelectron spectroscopy. The two-dimensional electron gas reveals itself via a narrow... more
The properties of a Sn-induced two-dimensional electron gas at the As-terminated InAs(111)B(1×1) surface was studied by synchrotron radiation photoelectron spectroscopy. The two-dimensional electron gas reveals itself via a narrow structure at the Fermi level, visible close to normal emission for tin coverage in the range 0.5 to 2 monolayers. Although this electron gas exhibits properties that in several respects resemble
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A dynamical origin for the Sn/Ge(111) room temperature phase has been revealed by the accurate structural determination of the (3 x 3) and (V3 x V3)R30° Sn/Ge(111) phases using photoelectron diffraction and surface x-ray diffraction... more
A dynamical origin for the Sn/Ge(111) room temperature phase has been revealed by the accurate structural determination of the (3 x 3) and (V3 x V3)R30° Sn/Ge(111) phases using photoelectron diffraction and surface x-ray diffraction experiments. Basically, two well distintive Sn sites are present in both phases, which build in a vertical corrugation of ~0.49 Å at the Sn layer. The temperature evolution of the width and intensity of the diffraction spots exhibits an order-disorder phase transition behavior, with little change in the magnitud of the atomic displacements. Hence, the room temperature Sn/Ge(111) phase is the result of a vertical flipping of the Sn adatoms.
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The growth mechanism and dependence on precursor conditions are vital for creation of high quality crystalline materials in many fields. Here the growth from nano sized quantum dots to micro crystalline methyl ammonium lead tri-iodide... more
The growth mechanism and dependence on precursor conditions are vital for creation of high quality crystalline materials in many fields. Here the growth from nano sized quantum dots to micro crystalline methyl ammonium lead tri-iodide (MAPbI3) perovskites prepared from isopropanol solution are reported. Isopropanol is more environmental friendly compared to the commonly used solvents DMF or DMSO, both with relatively high toxicity and the proposed method can be a useful new route to prepare hybrid perovskites. Three different molar ratio of MAPbI3 perovskite solution (MAI:PbI2 of 1:1, 2:1 and 0.5:1) was performed to give insights in the crystal formation mechanism also under non-stoichiometric conditions. Perovskite crystal growth is followed by TEM. From XRD powder diffraction the lattice constants has been determined and compared with results from electron diffraction (ED). Interestingly, there seems to be an occurrence of the cubic phase besides the common tetragonal phase at roo...
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... 99, No. 34, 1995 12895 (8) Cameron, SD; Dwyer, DJ J. Vac. Sci. Technol. A 1987,5, 651. ... 1979, 101, 2870. (18) Greenlief, CM; White, JM; KO, CS; Gorte, RJ J. Phys. (19) Chen, W.; Paul, J.; Barbieri, A.; VanHove, M.; Cameron, S.;... more
... 99, No. 34, 1995 12895 (8) Cameron, SD; Dwyer, DJ J. Vac. Sci. Technol. A 1987,5, 651. ... 1979, 101, 2870. (18) Greenlief, CM; White, JM; KO, CS; Gorte, RJ J. Phys. (19) Chen, W.; Paul, J.; Barbieri, A.; VanHove, M.; Cameron, S.; Dwyer, (20) Kasowski, RV; Tait, RH Phys. Rev. ...
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Adsorption of iodine on the Ge(100) (2×1) surface has been investigated by core level and valence band photoelectron spectroscopy and scanning tunnelling microscopy. Iodine binds to dimer atom dangling bonds without disrupting the dimers... more
Adsorption of iodine on the Ge(100) (2×1) surface has been investigated by core level and valence band photoelectron spectroscopy and scanning tunnelling microscopy. Iodine binds to dimer atom dangling bonds without disrupting the dimers at all coverages. At saturation a c(2×2) ordered layer of molecular iodine develops on top of a (2×2) ordered structure of atomic iodine binding to asymmetric
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... Sweden Lukas Severin Department ofPhysics, Uppsala Uniuersity, 751 21 Uppsala, Sweden Mats Gothelid and Mattias Hammar Physics III, Royal Institute of Technology, 100 44 Stockholm, Sweden Steve Cameron Corporate ...
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ABSTRACT In the present work, we study the bonding of 4-tert-butyl pyridine (4TBP) to the TiO2(110) surface using photoelectron spectroscopy (PES) and density functional theory (DFT) calculations. The results show that at low coverage,... more
ABSTRACT In the present work, we study the bonding of 4-tert-butyl pyridine (4TBP) to the TiO2(110) surface using photoelectron spectroscopy (PES) and density functional theory (DFT) calculations. The results show that at low coverage, 4TBP adsorbs preferentially on oxygen vacancies. The calculated adsorption energy at the vacancies is 120 kJ/mol larger than that on the five-fold-coordinated Ti4+ sites located in the rows on the TiO2 surface. The vacancy is “healed” by 4TBP, and the related gap state is strongly reduced through charge transfer into empty π* orbitals on the pyridine ring. This leads to a change in surface band bending by 0.2 eV toward lower binding energies. The band bending does not change with further 4TBP deposition when saturating the surface to monolayer coverage, where the TiO2 surface is effectively protected against further adsorption by the dense 4TBP layer.
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The growth and epitaxy of Sn on Ge(111) have been investigated using scanning tunneling microscopy (STM), low energy electron diffraction (LEED) and core level photoelectron spectroscopy for coverages ranging from 0.4 monolayers (ML) to... more
The growth and epitaxy of Sn on Ge(111) have been investigated using scanning tunneling microscopy (STM), low energy electron diffraction (LEED) and core level photoelectron spectroscopy for coverages ranging from 0.4 monolayers (ML) to above the critical coverage at 1.6 ML. At the lowest coverage a (√3 × √3)R30° reconstruction is formed at an annealing temperature of 250–300°C while an annealing above 500°C creates a dimer-adatom-stacking fault (DAS) (7 × 7) structure. In the (7 × 7) structure we argue that Sn occupies both adatom and dimer sites. A previously suggested difference in the (√3 × √3)R30° reconstruction at different coverages could not be revealed in our STM images and it seems likely that the structure is the same both at 0.4 and 0.7 ML Sn coverage. We also report the observation of a new superstructure, a (4 × √7) reconstruction in the submonolayer regime, which appears as a minority structure in disordered regions adjacent to a (5 × 5) DAS structure. Finally in the post-monolayer region a (3 × 2√3) structure, surrounded by vast areas of an amorphous tin overlayer, has been imaged by STM. As the coverage was increased, the amorphous layer completely covered the ordered (3 × 2√3) phase, which still could be observed in LEED. Additional room temperature deposition of Sn deteriorated the fractional order LEED spots presumably due to indiffusion of Sn from the interface as the critical coverage was surpassed.
Research Interests: Condensed Matter Physics, Materials Science, Quantum Physics, Chemistry, Surface Science, and 14 morePHOTOELECTRON SPECTROSCOPY, Adsorption, Scanning tunneling microscopy, Annealing, Tunneling, Surface Reconstruction, Low energy electron diffraction, Surface Structure, Room Temperature, Epitaxy, Indexation, X Ray Photoelectron Spectroscopy, Superstructure, and Scanning Tunneling Microscope (STM)
Zinc phthalocyanine (ZnPc) adsorbed on the InSb(001)-c(8×2) surface has been studied by scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). Coverages from sub-monolayer to monolayer (ML) have been investigated.... more
Zinc phthalocyanine (ZnPc) adsorbed on the InSb(001)-c(8×2) surface has been studied by scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). Coverages from sub-monolayer to monolayer (ML) have been investigated. The molecules form ordered structures on the reconstructed rows of the surface with the molecular plane parallel to the surface. A change in the electronic structure between the sub-ML and
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We show atomically resolved scanning tunneling microscopy (STM) images of charge density waves (CDWs) at room temperature together with angle-resolved photoelectron band-mapping of 1T-TaSe2. By comparing the results of these two... more
We show atomically resolved scanning tunneling microscopy (STM) images of charge density waves (CDWs) at room temperature together with angle-resolved photoelectron band-mapping of 1T-TaSe2. By comparing the results of these two techniques, we demonstrate the atomic structure of the CDW-features observed by the STM and atomic origin of the reconstructed band-structure in this material.
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ABSTRACT Results of scanning tunnelling microscopy (STM) show that two different kinds of surface structures coexist on the (110) surface of Pt80Fe20. The predominant structure corresponds well to the missing row type (1*2) reconstruction... more
ABSTRACT Results of scanning tunnelling microscopy (STM) show that two different kinds of surface structures coexist on the (110) surface of Pt80Fe20. The predominant structure corresponds well to the missing row type (1*2) reconstruction previously observed on, for example Pt(110), whereas the minority domains show a faintly buckled structure with approximately (1*1) geometry. Based on the STM images, the authors propose that the two domains have different surface chemical compositions and correspond to two different metallurgical phases known for the PtFe system at this composition.
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ABSTRACT The corrosion protection by self-assembled monolayers (SAMs) of hexanethiol and hexaneselenol has been explored on copper exposed to humid air containing formic acid, a corrosive environment relevant for indoor atmospheric... more
ABSTRACT The corrosion protection by self-assembled monolayers (SAMs) of hexanethiol and hexaneselenol has been explored on copper exposed to humid air containing formic acid, a corrosive environment relevant for indoor atmospheric corrosion. The kinetics of the formation of corrosion products on SAM covered copper was followed using in-situ infrared reflection/absorption spectroscopy (IRAS) and compared with that of bare copper. Both SAMs initially showed a corrosion protection ability. The prolonged exposure of hexanethiol copper resulted in a reduced formation rate of copper formate and copper hydroxide compared to bare copper, while on bare and hexaneselenol covered samples copper (I) oxide, copper formate, and copper hydroxide were observed. To assess the quality of the SAMs during the sample exposure, vibrational sum frequency spectroscopy (VSFS) was used. It was found that hexaneselenol molecules are locally removed from the surface during corrosion in contrast to their thiol counterparts. This created localized galvanic effects which resulted in an accelerated corrosion of selenol covered copper. X-ray photoelectron spectroscopy at elevated pressure demonstrated that the hexanethiol removed thin oxide layers upon adsorption. A contributing parameter to the enhanced corrosion inhibiting ability of hexanethiol could be its greater ability than hexaneselenol to bind to the copper surface during its deposition and sample exposure. (C) 2013 The Electrochemical Society.
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Ultrahigh vacuum-cleaved and as-grown surfaces of CdSe single crystals were investigated by scanning tunneling microscopy. The single crystals were grown by Reynolds-Green method. Striations and terrace-step structure have been found. The... more
Ultrahigh vacuum-cleaved and as-grown surfaces of CdSe single crystals were investigated by scanning tunneling microscopy. The single crystals were grown by Reynolds-Green method. Striations and terrace-step structure have been found. The surface atomic geometry was found and investigated. The (112(bar) 0) face geometry (structure formed by elementary cell of 0.75 x 0.7 nm(sup 2)) as well as other type structures
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Surface modification of reactive oxide substrates to obtain a less strongly interacting template for dye adsorption may be a way to enhance performance in dye-sensitized solar cells. In this work, we have investigated the electronic and... more
Surface modification of reactive oxide substrates to obtain a less strongly interacting template for dye adsorption may be a way to enhance performance in dye-sensitized solar cells. In this work, we have investigated the electronic and structural properties of 4,4(')-bipyridine (bipy) as modifier adsorbed on the TiO(2)(110) surface. The modified surface is then coated with iron phthalocyanine (FePc) and the properties of this heterostructure are investigated with synchrotron based photoelectron spectroscopy, x-ray absorption spectroscopy, and scanning tunneling microscopy. We find that a saturated monolayer consisting of standing bipy molecules with one nitrogen atom pointing outward is formed on the oxide surface. FePc adsorb in molecular chains along the [001] direction on top of bipy and ordered in a tilted arrangement with adjacent molecules partially overlapping. Already from the first layer, the electronic properties of FePc resemble those of multilayer films. FePc alone is oxidized on the TiO(2)(110) surface, but preadsorbed bipy prevents this reaction. The energy level lineup at the interface is clarified.
Research Interests: Engineering, Chemistry, Kinetics, Solar Cell, PHOTOELECTRON SPECTROSCOPY, and 15 moreChemical Physics, Medicine, Adsorption, Scanning tunneling microscopy, Physical sciences, Dye Sensitized Solar cell, Nitrogen, Iron, Electronic properties, CHEMICAL SCIENCES, Electrons, Pyridines, Structural Properties, Energy Levels, and Organic Compound
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The structure of the Pt50Ni50(100) surface was investigated by low energy electron diffraction (LEED) and scanning tunnelling spectroscopy (STM). Superstructures corresponding to 12 × 1 and 19 × 1 reconstructions were observed in the LEED... more
The structure of the Pt50Ni50(100) surface was investigated by low energy electron diffraction (LEED) and scanning tunnelling spectroscopy (STM). Superstructures corresponding to 12 × 1 and 19 × 1 reconstructions were observed in the LEED pattern, and these reconstructions were identified with atomic resolution by STM. The reconstructed surface layer has a quasi-hexagonal atomic mesh with almost (111) atomic density
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A dynamical origin for the Sn/Ge(111) room temperature phase has been revealed by the accurate structural determination of the ($3\times3$) and $(\sqrt{3}\times\sqrt{3})R30^{\circ}$ Sn/Ge(111) phases using surface x-ray diffraction... more
A dynamical origin for the Sn/Ge(111) room temperature phase has been revealed by the accurate structural determination of the ($3\times3$) and $(\sqrt{3}\times\sqrt{3})R30^{\circ}$ Sn/Ge(111) phases using surface x-ray diffraction experiments. Basically, two well distinct Sn sites are present in both phases, which build in a vertical corrugation of $\sim$0.49 \AA at the Sn layer. The temperature evolution of the width and intensity of the diffraction beams exhibits an order-disorder phase transition behavior, with little change in the magnitude of the atomic displacements. Hence, the room temperature Sn/Ge(111) phase is the result of a vertical flipping of the Sn adatoms.
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ABSTRACT Phthalocyanines (Pcs) are capable of converting sunlight into electric energy when adsorbed on TiO2 in a dye-sensitized solar cell. Of special interest in this type of cell is the energy level alignment as well as how molecules... more
ABSTRACT Phthalocyanines (Pcs) are capable of converting sunlight into electric energy when adsorbed on TiO2 in a dye-sensitized solar cell. Of special interest in this type of cell is the energy level alignment as well as how molecules adsorb on the surface as it determines the output of the cell. We investigated the FePc−TiO2(110) interface using scanning tunneling microscopy, synchrotron-based photoelectron spectroscopy, and X-ray absorption spectroscopy. We found a strong coupling of the first-layer FePc to the substrate resulting in an alteration of the electronic structure and charge transfer from the molecules. The FePc in the second layer is not severely affected by the bonding to the surface and has bulk-like electronic properties. The growth of FePc thin films proceeds in a layer plus island mode, and the molecular plane is parallel to the surface. The energy level alignment at the interface is determined, and the lowest unoccupied molecular orbital is found above the conduction band minimum of the oxide substrate.
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High resolution core level photoelectron spectroscopy (PES) and scanning tunneling microscopy (STM) have been used to study the adsorption and desorption of S on and off the Ge(100) surface. The previously proposed bridge adsorption site... more
High resolution core level photoelectron spectroscopy (PES) and scanning tunneling microscopy (STM) have been used to study the adsorption and desorption of S on and off the Ge(100) surface. The previously proposed bridge adsorption site of S is consistent with our results at low coverage. At saturation the substrate contains several GeSx species, with x=0.5 to 4. Both photoemission and
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... John Åhlund, Katharina Nilson, Pål Palmgren, Emmanuelle Göthelid, § Joachim Schiessling, Mats Göthelid, § Nils Mårtensson, and Carla Puglia* . ... 23) Kumpf, C.; Marks, LD; Ellis, D.; Smilgies, D.; Landemark, E.; Nielsen,... more
... John Åhlund, Katharina Nilson, Pål Palmgren, Emmanuelle Göthelid, § Joachim Schiessling, Mats Göthelid, § Nils Mårtensson, and Carla Puglia* . ... 23) Kumpf, C.; Marks, LD; Ellis, D.; Smilgies, D.; Landemark, E.; Nielsen, M.; Feidenhans'l, R.; Zegenhagen, J.; Bunk, ...
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ABSTRACT