A5024871823- Graphene research and applications
- Electron and X-Ray Spectroscopy Techniques
- Advanced Electron Microscopy Techniques and Applications
- Carbon Nanotubes in Composites
- Surface and Thin Film Phenomena
- Ion-surface interactions and analysis
- Semiconductor materials and devices
- Diamond and Carbon-based Materials Research
- 2D Materials and Applications
- Plasma Diagnostics and Applications
- Electronic and Structural Properties of Oxides
- Advancements in Battery Materials
- Boron and Carbon Nanomaterials Research
- Mass Spectrometry Techniques and Applications
- scientometrics and bibliometrics research
- Advanced X-ray Imaging Techniques
- Quantum and electron transport phenomena
- Fullerene Chemistry and Applications
- Advanced Materials Characterization Techniques
- Machine Learning in Materials Science
- Electrocatalysts for Energy Conversion
- Chemical and Physical Properties of Materials
- Molecular Junctions and Nanostructures
- MXene and MAX Phase Materials
- Advanced Chemical Physics Studies
University of Vienna
2016-2025
Rice University
2021
Oak Ridge National Laboratory
2021
University of Tübingen
2019
TU Wien
2016
Aalto University
2010-2014
VTT Technical Research Centre of Finland
2009
Helsinki Institute of Physics
2008
Tieto (Finland)
2008
<ns4:p>Simulation of transmission electron microscopy (TEM) images or diffraction patterns is often required to interpret experimental data. Since nuclear cores dominate scattering, the scattering potential typically described using independent atom model, which completely neglects valence bonding and its effect on transmitting electrons. As instrumentation has advanced, new measurements have revealed subtle details that were previously not accessible experiment.</ns4:p><ns4:p>...
We review the GPAW open-source Python package for electronic structure calculations. is based on projector-augmented wave method and can solve self-consistent density functional theory (DFT) equations using three different wave-function representations, namely real-space grids, plane waves, numerical atomic orbitals. The representations are complementary mutually independent be connected by transformations via grid. This multi-basis feature renders highly versatile unique among similar...
We demonstrate that 60-keV electron irradiation drives the diffusion of threefold-coordinated Si dopants in graphene by one lattice site at a time. First principles simulations reveal each step is caused an impact on C atom next to dopant. Although atomic motion happens below our experimental time resolution, stochastic analysis 38 such jumps reveals probability for their occurrence good agreement with simulations. Conversions from three- fourfold coordinated dopant structures and subsequent...
By combining ab initio simulations with state-of-the-art electron microscopy and energy loss spectroscopy, we study the mechanism of beam damage in nitrogen-doped graphene carbon nanotubes. Our results show that incorporation nitrogen atoms noticeable knock-on these structures already at an acceleration voltage 80 kV, which essentially no is created pristine corresponding doses. Contrary to early estimate predicting rapid destruction via sputtering atoms, case substitutional doping,...
The direct manipulation of individual atoms in materials using scanning probe microscopy has been a seminal achievement nanotechnology. Recent advances imaging resolution and sample stability have made transmission electron promising alternative for single-atom covalently bound materials. Pioneering experiments an atomically focused beam demonstrated the directed movement silicon over handful sites within graphene lattice. Here, we achieve much greater degree control, allowing us to...
Incorporating heteroatoms into the graphene lattice may be used to tailor its electronic, mechanical and chemical properties, although directly observed substitutions have thus far been limited incidental Si impurities P, N B dopants introduced using low-energy ion implantation. We present here heaviest impurity date, namely 74Ge+ ions implanted monolayer graphene. Although sample contamination remains an issue, atomic resolution scanning transmission electron microscopy imaging quantitative...
One of the keys behind success modern semiconductor technology has been ion implantation silicon, which allows its electronic properties to be tailored. For similar purposes, heteroatoms have introduced into carbon nanomaterials both during growth and using post-growth methods. However, due nature samples, it challenging determine whether incorporated lattice as intended, with direct observations so far being limited N B dopants, incidental Si impurities. Furthermore, these materials is more...
Atomic engineering is envisioned to involve selectively inducing the desired dynamics of single atoms and combining these steps for larger-scale assemblies. Here, we focus on first part by surveying single-step graphene dopants, primarily phosphorus, caused electron irradiation both in experiment simulation, develop a theory describing probabilities competing configurational outcomes depending postcollision momentum vector primary knock-on atom. The predicted branching ratio transformations...
We present a quantitatively accurate machine-learning (ML) model for the computational prediction of core-electron binding energies, from which X-ray photoelectron spectroscopy (XPS) spectra can be readily obtained. Our combines density functional theory (DFT) with
Replacing traditional journals with a more modern solution is not new idea. Here, we propose ways to overcome the social dilemma underlying decades of inaction. Any needs only resolve current problems but also be capable preventing takeover by corporations: it replace decentralized, resilient, evolvable network that interconnected open standards and open-source norms under governance scholarly community. It monopolies connected genuine, functioning well-regulated market. In this market,...
Electronic charge transfer at the atomic scale can reveal fundamental information about chemical bonding, but is far more challenging to directly image than structure. The density dominated by nuclei, with bonding causing only a small perturbation. Thus detecting any change due requires higher level of sensitivity imaging structure and overall density. Here we achieve required detect in both pristine defected monolayer WS2 using high dose efficiency electron ptychography its ability correct...
The {\AA}ngstr\"om-sized probe of the scanning transmission electron microscope can visualize and collect spectra from single atoms. This unambiguously resolve chemical structure materials, but not their isotopic composition. Here we differentiate between two isotopes same element by quantifying how likely energetic imaging electrons are to eject First, measure displacement probability in graphene grown either $^{12}$C or $^{13}$C describe process using a quantum mechanical model lattice...
X-ray photoelectron spectroscopy (XPS) is a widely used tool for studying the chemical composition of materials and it standard technique in surface science technology. XPS particularly useful characterizing nanostructures such as carbon nanomaterials due to their reduced dimensionality. In order assign measured binding energies specific bonding environments, reference energy values need be known. Experimental measurements core level signals elements present novel graphene have often been...
Surface impurities and contamination often seriously degrade the properties of two-dimensional materials such as graphene. To remove contamination, thermal annealing is commonly used. We present a comparative analysis treatments in air vacuum, both ex situ "pre-situ", where an ultra-high vacuum treatment chamber directly connected to aberration-corrected scanning transmission electron microscope. While do it challenging obtain atomically clean surfaces after ambient transfer. However,...
The ultimate performance - ratio of electrical conductivity to optical absorbance single- walled carbon nanotube (SWCNTs) transparent conductive films (TCFs) is an issue considerable application relevance. Here, we present direct experimental evidence that SWCNT bundling detrimental for their performance. We combine floating catalyst synthesis non-bundled, high-quality SWCNTs with aggregation chamber, in which bundles mean diameters ranging from 1.38 2.90 nm are formed identical 3 microns...
Studying the atomic structure of intrinsic defects in two-dimensional transition metal dichalcogenides is difficult since they damage quickly under intense electron irradiation transmission microscopy (TEM). However, this can also lead to insights into creation and their atom-scale dynamics. We first show that MoTe 2 monolayers without protection indeed degrade during scanning TEM (STEM) imaging, discuss observed atomic-level dynamics, including a transformation from 1H phase 1T', three-fold...
Simulation of transmission electron microscopy (TEM) images or diffraction patterns is often required to interpret experimental data. Since nuclear cores dominate scattering, the scattering potential typically described using independent atom model, which completely neglects valence bonding and its effect on transmitting electrons. As instrumentation has advanced, new measurements have revealed subtle details that were previously not accessible experiment. We created an open-source...
Heterostructures composed of 2D materials are already opening many new possibilities in such fields technology as electronics and magnonics, but far more could be achieved if the number diversity were increased. So far, only a few dozen crystals have been extracted from that exhibit layered phase ambient conditions, omitting entirely large may exist at other temperatures pressures. This work demonstrates how structures can stabilized van der Waals (vdw) stacks under room temperature via...
Diamond and graphene are carbon allotropes with starkly different physical characteristics. Their combination into graphene-on-diamond heterostructures could benefit from the complementary properties of both components. Graphitization single-crystalline diamond surfaces is a promising synthesis route, but clear understanding growth or graphite solid sources so far missing. Using aberration-corrected transmission electron microscopy, Raman spectroscopy, electrical transport measurements, we...
Processes of research evaluation are coming under increasing scrutiny, with detractors arguing that they have adverse effects on quality, and support a culture competition to the detriment collaboration. Based three personal perspectives, we consider how current systems lock early career researchers their supervisors into practices deemed necessary progress academic careers within frameworks. We reflect main areas in which changes would enable better evolve; many align open science. In...
Abstract Understanding electron irradiation effects is vital not only for reliable transmission microscopy characterization, but increasingly also the controlled manipulation of 2D materials. The displacement cross sections monolayer hexagonal boron nitride (hBN) are measured using aberration‐corrected scanning in near ultra‐high vacuum at primary beam energies between 50 and 90 keV. Damage rates below 80 keV up to three orders magnitude lower than previously edges under poorer residual...