A5084454934- Graphene research and applications
- Perovskite Materials and Applications
- Solid-state spectroscopy and crystallography
- Surface Chemistry and Catalysis
- Advancements in Battery Materials
- Molecular Junctions and Nanostructures
- 2D Materials and Applications
- X-ray Diffraction in Crystallography
- Advanced Chemical Physics Studies
- Surface and Thin Film Phenomena
- Chalcogenide Semiconductor Thin Films
- Boron and Carbon Nanomaterials Research
- Quantum Dots Synthesis And Properties
- Topological Materials and Phenomena
- Crystallization and Solubility Studies
- ZnO doping and properties
- Thermal Expansion and Ionic Conductivity
- Multiferroics and related materials
- Hydrogen Storage and Materials
- Optical and Acousto-Optic Technologies
- Crystal Structures and Properties
- Diamond and Carbon-based Materials Research
- Fusion materials and technologies
- Organic and Molecular Conductors Research
- Optical properties and cooling technologies in crystalline materials
University of Freiburg
2021-2024
Fraunhofer Institute for Mechanics of Materials
2021-2024
Friedrich-Alexander-Universität Erlangen-Nürnberg
2011-2021
Max Planck Institute for the Structure and Dynamics of Matter
2018-2020
University of Pennsylvania
2016-2020
University of Würzburg
2019
WZB Berlin Social Science Center
2019
Philadelphia University
2018
California University of Pennsylvania
2018
Institute of Physics
2017
Quantum and dielectric confinement effects in Ruddlesden-Popper 2D hybrid perovskites create excitons with a binding energy exceeding 150 meV. We exploit the large exciton to study carrier dynamics as well electron–phonon coupling (EPC) using absorption photoluminescence (PL) spectroscopies. At temperatures <75 K, we resolve splitting of excitonic PL into multiple regularly spaced resonances every 40–46 meV, consistent EPC phonons located on organic cation. also 14 meV spacing, accord mixed...
Abstract The fabrication of nanostructures in a bottom-up approach from specific molecular precursors offers the opportunity to create tailored materials for applications nanoelectronics. However, formation defect-free two-dimensional (2D) covalent networks remains challenge, which makes it difficult unveil their electronic structure. Here we report on hierarchical on-surface synthesis nearly 2D architectures with carbonyl-functionalized pores Au(111), is investigated by low-temperature...
The doping of graphene to tune its electronic properties is essential for further use in carbon-based electronics. Adapting strategies from classical silicon-based semiconductor technology, we the incorporation heteroatoms 2D network as a straightforward way achieve this goal. Here, report on synthesis boron-doped Ni(111) chemical vapor deposition process triethylborane one hand and by segregation boron bulk substrate crystal other hand. environment was determined x-ray photoelectron...
We report on experimental and theoretical investigations of nitrogen-doped graphene. The incorporation nitrogen was achieved during chemical-vapor deposition Ni(111) using pyridine as a precursor. obtained graphene layers were investigated photoelectron spectroscopy. By studying C $1s$ N core levels, we show that the content is influenced by growth temperature determine atomic arrangement atoms. Valence-band spectra leads to broadening photoemission lines shift $\ensuremath{\pi}$ band....
Abstract Understanding the adsorption and reaction between hydrogen graphene is of fundamental importance for developing graphene‐based concepts storage chemical functionalization by hydrogenation. Recently, theoretical studies single‐sided hydrogenated graphene, so called graphone, predicted it to be a promising semiconductor applications in electronics. Here, we report on synthesis graphone bound Ni(111) surface. We investigate formation process X‐ray photoelectron spectroscopy (XPS),...
The authors investigate the effects of substitutional metal doping on BiFeO${}_{3}$ by accurate first-principles calculations. In a high-throughput fashion, they screen large parts periodic table, providing unique view site preference, type, and oxidation states, enabling strategies for future multifunctional oxide electronics.
Abstract The properties of van der Waals (vdW) materials often vary dramatically with the atomic stacking order between layers, but this can be difficult to control. Trilayer graphene (TLG) stacks in either a semimetallic ABA or semiconducting ABC configuration gate-tunable band gap, latter has only been produced by exfoliation. Here we present chemical vapor deposition approach TLG growth that yields greatly enhanced fraction and size domains. key insight is substrate curvature stabilize...
The electronic coupling as well the attenuation factor (β), which depends primarily on nature of molecular bridge and is used a benchmark to test wire behavior, have been determined in systematic study carried out series ZnP/C60 conjugates connected through [2,2′]paracyclophane−oligophenylenevinylene (pCp-oPPV). convergent synthesis involves Horner−Emmons olefination reactions or double palladium-catalized Heck-type reactions. ZnP−pCp−C60 were finally obtained by 1,3-dipolar cycloaddition...
Layered perovskites open a plethora of possibilities for tuning organometallic halide perovskite (OMHP) properties via the incorporation larger organic cations. Promising applications this increased structural freedom include enhanced chemical stability and tunable exciton binding. Owing to cation, crystal electronic structures vary with layer stacking, having layered bulk monolayer as limiting cases. Using ab initio calculations, here we study atomic such material, (C6H5C2H4NH3)2PbI4, which...
Scanning tunneling spectroscopy and density-functional theory reveal an unoccupied electronic state that is delocalized along the entire organometallic Ag-bis-acetylide network.
Perovskites are a rich family of functional materials with many interesting physical properties. Usually, they contain two cationic species on the A- and B-sites, surrounded by anionic X-site, but compounds also known that invert ion types respective lattice sites (inverse perovskites). Recently, conventional perovskites one inorganic cation substituted an organic molecule were intensively studied due to promising performance CH3NH3PbI3 based solar cells. Here, for first time, we take...
Graphyne-based two-dimensional (2D) carbon allotropes feature extraordinary physical properties; however, their synthesis as crystalline single-layered materials has remained challenging. We report on the fabrication of large-area organometallic Ag-bis-acetylide networks and structural electronic properties Ag(111) using low-temperature scanning tunneling microscopy combined with density functional theory (DFT) calculations. The metalated graphyne-based are robust at room temperature...
Cs 2 AgBiBr 6 is a stable halide double perovskite with bandgap of about 2.2 eV. Therefore, it intensively studied as potential lead‐free alternative to hybrid solar cell absorber materials such methylammonium lead iodide. However, power conversion efficiencies cells this material have not yet exceeded 3%. A detailed understanding the electronic structure difficult, due variance reported data and experimental well theoretical difficulties that occur in going beyond qualitative an indirect...
The synthesis of single-layer graphene sheets on metal surfaces can be carried out routinely nowadays. energetic alignment the band structure, including position Dirac point relative to Fermi level metal, and subsequently, doping sheet, depends crucially graphene-metal distance specific considered. These dependencies are studied with density-functional theory considering as typical Au(111), Ni(111), Au/Ni(111). In latter case, a single layer gold is intercalated between Ni(111) surface...
We investigate the reactivity of hexagonal boron nitride (h-BN) on a Ni(1 1 1) single crystal towards atomic hydrogen over wide exposure range. Near edge x-ray absorption fine structure and photoelectron spectroscopy (XPS) show that for low exposures hydrogenation h-BN sheet is found. In contrast, intercalation between substrate occurs high exposures. For intermediate regimes, mixture observed. From temperature-programmed desorption XPS experiments, we conclude covalently bound to rather...
Demonstrated here is a supramolecular approach to fabricate highly ordered monolayered hydrogen- and halogen-bonded graphyne-like two-dimensional (2D) materials from triethynyltriazine derivatives on Au(111) Ag(111). The 2D networks are stabilized by N⋅⋅⋅H-C(sp) bonds N⋅⋅⋅Br-C(sp) the triazine core. structural properties binding energies of graphynes have been investigated scanning tunneling microscopy in combination with density-functional theory calculations. It revealed that lead...
The Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation to the exchange-correlation energy is widely used in materials science. For many solids it somewhat overestimates lattice constants and underestimates cohesive energies. What attraction among ions missing PBE? ionic heavy metals, a detailed analysis shows that answer van der Waals (vdW) interaction arising from electric charge fluctuations on different ions. Our vdW correction PBE short-range damped long-range screened...
We investigate the capability of low-coordinated sites on small model clusters to act as active centers for hydrogen storage. A set magic with formula (XY)6 (X = Mg, Ba, Be, Zn, Cd, Na, Li, B and Y O, Se, S, F, I, N) a "drumlike" hexagonal shape showing low coordination number three was screened. Oxide turned out be most promising candidates For these ionic compounds we explored suitability different van der Waals (vdW) corrections density-functional calculations by comparing respective H2...
An efficient and accurate description of the electronic structure a strongly correlated metal-oxide semiconductor like NiO has been notoriously difficult. Here, we study capabilities limitations two frequently employed correction schemes, DFT+Uon-site DFT+1/2 self-energy correction. While both methods individually are unable to provide satisfactory results, in combination they very good all relevant physical quantities. Since cope with different shortcomings common density-functional theory...
The intercalation of a graphene layer adsorbed on metal surface by gold or other metals is standard procedure. While it was previously shown that pristine, i.e., undoped, and nitrogen-doped sheets can be decoupled from nickel substrate with atoms in order to produce quasi-free-standing graphene, we find the behavior for boron-doped Ni(111) more complex: low boron contents (2–5%) lattice only partial occurs higher (up 20%) no observed. In understand this different behavior, density functional...
To cover future green energy needs, new absorber materials must augment silicon in the established photovoltaic (PV) technology. (Hybrid) perovskites emerged as for this purpose, but are often plagued by long-term stability issues and contain elements that critical with respect to health or material availability. Identifying stable materials, which reach equally high PV performance best of their class do not any element, remains vital. This quest requires research, fabrication optimization...
We recently introduced a new class of perovskites, with inorganic anions on the A- and B-sites an organic cation X-site, so-called inverse-hybrid perovskites (IHPs). found compounds that are predicted to be stable, possess large polarization, span wide range electronic properties. Here, we present materials search strategy enabled these results. demonstrate design principles in terms ion site composition. Overall, consider elements from most main groups periodic table, investigating their...