A5084801808- Electronic and Structural Properties of Oxides
- Catalytic Processes in Materials Science
- ZnO doping and properties
- Iron oxide chemistry and applications
- Semiconductor materials and devices
- Gas Sensing Nanomaterials and Sensors
- Surface and Thin Film Phenomena
- Copper-based nanomaterials and applications
- Electron and X-Ray Spectroscopy Techniques
- Catalysis and Oxidation Reactions
- Advanced Photocatalysis Techniques
- Magnetic and transport properties of perovskites and related materials
- Advanced Chemical Physics Studies
- Electrocatalysts for Energy Conversion
- TiO2 Photocatalysis and Solar Cells
- Magnetic Properties and Synthesis of Ferrites
- Machine Learning in Materials Science
- nanoparticles nucleation surface interactions
- Advanced Condensed Matter Physics
- Advanced Materials Characterization Techniques
- Magnetic properties of thin films
- Force Microscopy Techniques and Applications
- Molecular Junctions and Nanostructures
- Ion-surface interactions and analysis
- Chemical and Physical Properties of Materials
TU Wien
2016-2025
Robert Bosch (Germany)
2024
Institut für Technische und Angewandte Physik (Germany)
2024
FH Campus Wien
2014-2020
University of Vienna
2020
Austrian Economics Center
2017
Tulane University
2005-2015
Institute of Applied Physics
2012
Interface (United States)
2012
University of Pennsylvania
2012
Nitrogen doping-induced changes in the electronic properties, defect formation, and surface structure of ${\mathrm{TiO}}_{2}$ rutile(110) anatase(101) single crystals were investigated. No band gap narrowing is observed, but N doping induces localized $2p$ states within just above valence band. present a N(III) state, which facilitates formation oxygen vacancies Ti $3d$ at elevated temperatures. The increased O vacancy triggers $1\ifmmode\times\else\texttimes\fi{}2$ reconstruction rutile...
Oxygen (O2) adsorbed on metal oxides is important in catalytic oxidation reactions, chemical sensing, and photocatalysis. Strong adsorption requires transfer of negative charge from oxygen vacancies (VOs) or dopants, for example. With scanning tunneling microscopy, we observed, transformed, and, conjunction with theory, identified the nature O2 molecules (101) surface anatase (titanium oxide, TiO2) doped niobium. VOs reside exclusively bulk, but pull them to a strongly negatively charged...
The (1x1) terminated (0001)-Zn surface of wurtzite ZnO was investigated with scanning tunneling microscopy. is characterized by the presence nanosized islands a size-dependent shape and triangular holes single-height, O-terminated step edges. It proposed that resulting overall decrease Zn concentration stabilizes this polar surface. Ab initio calculations test geometries predict triangularly shaped reconstructions over wide range oxygen hydrogen chemical potentials. formation these appears...
We have examined the interaction of molecular oxygen with TiO2(110) surface using temperature-programmed desorption (TPD), isotopic labeling studies, sticking probability measurements, and electron energy loss spectroscopy (ELS). Molecular does not adsorb on in temperature range between 100 300 K unless vacancy sites are present. These defects generated by annealing crystal at 850 K, can be quantified reliably water TPD. Adsorption O2 120 a 8% vacancies (about 4 × 1013 sites/cm2) occurs an...
A combination of scanning tunneling microscopy and spectroscopy density functional theory is used to characterize excess electrons in TiO2 rutile anatase, two prototypical materials with identical chemical composition but different crystal lattices. In rutile, can localize at any lattice Ti atom, forming a small polaron, which easily hop neighboring sites. contrast, anatase prefer free-carrier state, only be trapped near oxygen vacancies or form shallow donor states bound Nb dopants. The...
We have used oxygen-plasma-assisted molecular-beam epitaxy (OPA-MBE) to grow CoxTi1−xO2 anatase on SrTiO3(001) for x=∼0.01–0.10, and measured the structural, compositional, magnetic properties of resulting films. Whether epitaxial or polycrystalline, these films are ferromagnetic semiconductors at above room temperature. However, structural depend critically Co distribution, which varies widely with growth conditions. is substitutional in lattice +2 formal oxidation state CoxTi1−xO2. The...
We have studied the stoichiometric (annealed in oxygen), slightly oxygen-deficient vacuum), and highly defective (sputtered with Ar+) TiO2(110) surfaces their reactivities to molecular oxygen, water, 50-eV hydrogen ions using x-ray photoelectron spectroscopy (XPS) low-energy ion scattering (LEIS). The use of isotopically labeled 18O enables us distinguish adsorbed oxygen from lattice concentration surface vacancies is titrated by 18O2 adsorption. LEIS (1-keV He+) used analyze chemical...
Iron oxides play an increasingly prominent role in heterogeneous catalysis, hydrogen production, spintronics, and drug delivery. The surface or material interface can be performance-limiting these applications, so it is vital to determine accurate atomic-scale structures for iron understand why they form. Using a combination of quantitative low-energy electron diffraction, scanning tunneling microscopy, density functional theory calculations, we show that ordered array subsurface vacancies...
Understanding how the local environment of a "single-atom" catalyst affects stability and reactivity remains challenge. We present an in-depth study copper1, silver1, gold1, nickel1, palladium1, platinum1, rhodium1, iridium1 species on Fe3O4(001), model support in which all metals occupy same twofold-coordinated adsorption site upon deposition at room temperature. Surface science techniques revealed that CO strength single metal sites differs from respective surfaces supported clusters....
A preference for acids When titanium dioxide surfaces are exposed to water under ambient conditions, an ordered overlayer forms. Balajka et al. studied this process with scanning tunneling microscopy and x-ray photoelectron spectroscopy adsorption vacuum conditions in air (see the Perspective by Park). The was only formed air, result of organic (formic acetic acids). Although other species such as alcohols were present much higher concentrations bidentate entropic effects favored acid...
Savitzky-Golay (SG) filtering, based on local least-squares fitting of the data by polynomials, is a popular method for smoothing and calculations derivatives noisy data. At frequencies above cutoff, SG filters have poor noise suppression; this unnecessarily reduces signal-to-noise ratio, especially when calculating In addition, filtering near boundaries range prone to artifacts, which are strong using We show how these disadvantages can be avoided while keeping advantageous properties...
We present atomically resolved scanning tunneling microscopy (STM) images from Ti${\mathrm{O}}_{2}$(110) surfaces. After annealing nearly perfect stoichiometric $1\ifmmode\times\else\texttimes\fi{}1$ surfaces to elevated temperatures in ultrahigh vacuum, randomly distributed oxygen vacancies are observed. The apparent shape of these defects provides strong evidence that the STM is imaging undercoordinated Ti atoms, as do first-principles pseudopotential calculations electronic states...
Density-functional calculations for the (0001)-Zn surface of wurtzite ZnO are reported. Different stabilization mechanisms, such as metallization layer, adsorption OH groups or O adatoms, formation Zn vacancies, and large scale triangular reconstructions considered. The indicate that isolated vacancies adatoms unfavorable compared to reconstructions. In absence hydrogen, these features stable under any realistic temperature pressure. When hydrogen is present, reconstruction lifted, hydroxyl...
The interaction of water and methanol with well-defined (1 × 1) terminated surfaces anatase-TiO2(101) were investigated temperature-programmed desorption (TPD) X-ray photoelectron spectroscopy (XPS). For water, three states observed in the TPD spectra at 160, 190, 250 K. peaks assigned to multilayer adsorbed 2-fold-coordinated O, 5-fold-coordinated Ti, respectively. for more complicated. methanol, five 135, 170, 260, 410, 610 methoxy Ti step edges, XPS results indicated that predominantly...