A5059074436- Boron and Carbon Nanomaterials Research
- Graphene research and applications
- 2D Materials and Applications
- Perovskite Materials and Applications
- Nanowire Synthesis and Applications
- MXene and MAX Phase Materials
- Carbon Nanotubes in Composites
- Quantum Dots Synthesis And Properties
- Advancements in Semiconductor Devices and Circuit Design
- Boron Compounds in Chemistry
- Chalcogenide Semiconductor Thin Films
- Advancements in Battery Materials
- Advanced Chemical Physics Studies
- Graphene and Nanomaterials Applications
- Semiconductor materials and interfaces
- Spectroscopy Techniques in Biomedical and Chemical Research
- Thermal properties of materials
- Machine Learning in Materials Science
- Advanced ceramic materials synthesis
- Catalytic Processes in Materials Science
- Organic and Molecular Conductors Research
- Electron and X-Ray Spectroscopy Techniques
- Electronic and Structural Properties of Oxides
- Semiconductor Quantum Structures and Devices
- Nanopore and Nanochannel Transport Studies
Technische Universität Dresden
2012-2023
University of Warsaw
2021
Columbia University
2013-2016
Max Bergmann Zentrum für Biomaterialien
2011-2016
Osaka University
2016
Leibniz Institute of Polymer Research
2015
Max Planck Institute for Solid State Research
2004-2008
Max Planck Society
2006-2008
University of Stuttgart
2006
Universität Greifswald
2004
Molybdenum disulfide bilayers with well-defined interlayer twist angle were constructed by stacking single-crystal monolayers. Varying results in strong tuning of the indirect optical transition energy and second-harmonic generation weak direct energies Raman mode frequencies. Electronic structure calculations show separation changes due to repulsion between sulfur atoms, resulting shifts energies. These that alignment is a crucial variable tailoring properties two-dimensional heterostructures.
Based on a numerical ab initio study, we discuss structure model for broad boron sheet, which is the analog of single graphite and precursor nanotubes. The sheet has linear chains $sp$ hybridized $\ensuremath{\sigma}$ bonds lying only along its armchair direction, high stiffness, anisotropic properties. puckering explained as mechanism to stabilize bonds. bond properties lead two-dimensional reference lattice structure, rectangular rather than triangular. As consequence chiral angles related...
We critically discuss the stability of edge states and magnetism in zigzag graphene nanoribbons (ZGNRs). point out that magnetic might not exist real systems, show there are at least three very natural mechanisms - reconstruction, passivation, closure which dramatically reduce effect ZGNRs or even totally eliminate them. Even if systems with could be made, intrinsic would stable room temperature. Charge doping presence defects further destabilize such systems.
Graphene has a multitude of striking properties that make it an exceedingly attractive material for various applications, many which will emerge over the next decade. However, one most promising applications lie in exploiting its peculiar electronic are governed by electrons obeying linear dispersion relation. This leads to observation half integer quantum hall effect and absence localization. The latter is graphene-based field transistors. if graphene be future electronics, then significant...
The transport properties, work functions, electronic structure, and structural stability of boron nanotubes with different lattice structures, radii, chiralities are investigated theoretically. As the atomic structure related sheets is still under debate, three probable classes (nanotubes derived from α-sheet, buckled triangular sheet, distorted hexagonal sheet) considered. For comparison recent measurements [J. Mater. Chem. 2010, 20, 2197], intrinsic conductance ideal large diameters (D ≈...
External fields are a powerful tool to probe optical excitations in material. The linear energy shift of an excitation magnetic field is quantified by its effective g-factor. Here we show how exciton g-factors and their sign can be determined converged first principles calculations. We apply the method monolayer excitons semiconducting transition metal dichalcogenides interlayer MoSe$_2$/WSe$_2$ heterobilayers obtain good agreement with recent experimental data. precision our allows assign...
Using angle-resolved photoemission on micrometer-scale sample areas, we directly measure the interlayer twist angle-dependent electronic band structure of bilayer molybdenum-disulfide (MoS2). Our measurements, performed arbitrarily stacked MoS2 flakes prepared by chemical vapor deposition, provide direct evidence for a downshift quasiparticle energy valence at Brillouin zone center (Γ̅ point) with angle, up to maximum 120 meV angle ∼40°. measurements enable extraction hole effective mass as...
We report the experimental observation of radiative recombination from Rydberg excitons in a two-dimensional semiconductor, monolayer WSe2, encapsulated hexagonal boron nitride. Excitonic emission up to 4s excited state is directly observed photoluminescence spectroscopy an out-of-plane magnetic field 31 T. confirm progressively larger exciton size for higher energy states through diamagnetic shift measurements. This also enables us estimate 1s binding be about 170 meV, which significantly...
Abstract Manipulating the interlayer twist angle is a powerful tool to tailor properties of layered two-dimensional crystals. The has determinant impact on these systems’ atomistic structure and electronic properties. This includes corrugation individual layers, formation stacking domains other structural elements, changes due atomic reconstruction superlattice effects. However, how change with angle, θ , not yet well understood. Here, we monitor twisted bilayer (tBL) MoS 2 characteristics...
The mechanism of the selective dispersion single-walled carbon nanotubes (CNTs) by polyfluorene polymers is studied in this paper. Using extensive molecular dynamics simulations, it demonstrated that diameter selectivity result a competition between bundling CNTs and adsorption on CNT surfaces. preference for certain diameters corresponds to local minima binding energy difference these two processes. Such dependence occur due abrupt changes CNT's coverage with their calculated positions are...
Stable excitons in semiconductor monolayers such as transition-metal dichalcogenides (TMDCs) enable and motivate fundamental research well the development of room-temperature optoelectronics applications. The newly discovered layered magnetic materials present a unique opportunity to integrate optical functionalities with magnetism. We predict that large class antiferromagnetic semiconducting MPX$_3$ family exhibit giant excitonic binding energies, making them suitable platforms for...
Defects usually play an important role in tuning and modifying various properties of semiconducting or insulating materials. Therefore, we study the impact point line defects on electronic structure optical monolayers using density-functional methods. The different types form states that are spatially localized defect. strongly nature is reflected weak interactions between individual defects, a dependence defect formation energy concentration separation, sharply peaked spectrum. monolayer...
A well-defined cluster containing 12 equivalent platinum atoms was prepared by ion exchange of an NaY zeolite, followed hydrogen reduction. It characterized electron paramagnetic resonance (EPR) spectroscopy, hyperfine sublevel correlation (HYSCORE), and theoretical calculations. Combing the results experiments with density functional calculations, likely structure this is icosahedral Pt13Hm, possibly a low positive charge. The adsorbed H/D on Pt surface can be exchanged reversibly at room...
We present the results of our recent parametrization boron–boron and boron–hydrogen interactions for self-consistent charge density-functional-based tight-binding (SCC-DFTB) method. To evaluate performance, we compare SCC-DFTB to full density functional theory (DFT) wave-function-based semiempirical methods (AM1 MNDO). Since advantages emerge especially large systems, calculated molecular systems boranes pure boron nanostructures. Computed bond lengths, angles, vibrational frequencies are...
Despite recent successes in the synthesis of boron nanotubes (BNTs), atomic arrangement their walls has not yet been determined and many questions about basic properties do remain. Here, we unveil dynamical stability BNTs by means first-principles molecular dynamics simulations. We find that free-standing, single-wall with diameters larger than 0.6 nm are thermally stable at experimentally reported temperature 870$^\circ$C higher. The found to have a variety different mixed...
The success of future nanotechnologies will strongly depend on our ability to control the structure materials atomic scale. For carbon nanotubes it turns out that one their structural parameters—the chirality—may not be controlled during synthesis. We explain basic reason for this defect and show novel classes like boron nanotubes, which are related sheets with anisotropic in-plane mechanical properties, could actually overcome these problems. Our results further suggest extended searches...
In heterobilayers consisting of different transition‐metal dichalcogenide (TMDC) monolayers, optically excited electron–hole pairs can be spatially separated into the adjacent layers due to a type‐II band alignment. However, they remain Coulomb correlated and form interlayer excitons (ILEs), which recombine radiatively. While these ILEs are observed in several TMDC material combinations, their characters properties depend on specific system. Herein, some peculiarities demonstrated by...
Solventless thermolysis of molecular precursors followed by liquid phase exfoliation allows access to two-dimensional IV-VI semiconductor nanomaterials hitherto unreachable a scalable processing pathway. Firstly, the use metal dithiocarbamate produce bulk alloys in series Pb1-x Sn x S (0 ≤ 1) is demonstrated. The powders are characterised powder X-ray diffraction (pXRD), Raman spectroscopy, scanning electron microscopy (SEM) and energy dispersive (EDX) spectroscopy. It was found that there...
The recent discovery of borophene, a two-dimensional allotrope boron, raises many questions about its structure and chemical physical properties. Boron has high affinity to oxygen but little is known the oxidation behavior borophene. Here we use first principles calculations study phase diagram free-standing, $\mathrm{B_{1-x}O_x}$ for compositions ranging from $x=0$ $x=0.6$, which correspond borophene $\mathrm{B_2O_3}$ sheets, respectively. Our results indicate that no stable compounds...