arXiv subjects

Christina Trautmann

Publications and source records attributed to Christina Trautmann.

10 recordsLinked to original sources

arXiv2025

Influence of carbon dioxide and water concentration on terbium thin films produced by Molecular Plating

Terbium and thulium thin films were produced by Molecular Plating under controlled conditions to elucidate a possible influence of water and carbon dioxide present in the plating solution. Platings were made in a glovebox with variable concentration of residual water and \ce{CO2} in a controlled inert atmosphere to study the impact on the quality of the produced thin films and on deposition yields. The morphology of the thin films was analyzed by scanning electron microscopy. The deposition yield was determined by neutron activation analysis at the research reactor TRIGA Mainz. Chemical analysis of the deposited layers was conducted using a combination of infrared, Raman and X-ray photoelectron spectroscopy. The Raman and IR spectra reveal the formation of hydroxides, oxides and carbonates. Water in the plating solution affects the quality of the thin films when its concentration exceeds 1 vol.-\%. The presence of \ce{CO2} leads to an increased carbonate content, which negatively influences the film quality

cond-mat.mtrl-sci↗

arXiv2025

Characterization of ion track etched conical nanopores in thermal and PECVD SiO$_{2}$ using small angle X-ray scattering

Conical nanopores in amorphous SiO$_{2}$ thin films fabricated using the ion track etching technique show promising potential for filtration, sensing and nanofluidic applications. The characterization of the pore morphology and size distribution, along with its dependence on the material properties and fabrication parameters, is crucial to designing nanopore systems for specific applications. Here, we present a comprehensive study of track-etched nanopores in thermal and plasma-enhanced chemical vapor deposited (PECVD) SiO$_{2}$ using synchrotron-based small-angle X-ray scattering (SAXS). We present a new approach for analyzing the complex highly anisotropic 2-dimensional SAXS patterns of the pores by reducing the analysis to two orthogonal 1-dimensional slices of the data. The simultaneous fit of the data enables an accurate determination of the pore geometry and size distribution. The analysis reveals substantial differences between the nanopores in thermal and PECVD SiO$_{2}$. The track-to-bulk etching rate ratio is significantly different for the two materials, producing nanopores with cone angles that differ by almost a factor of 2. Furthermore, thermal SiO$_2$ exhibits an exceptionally narrow size distribution of only ~2-4%, while PECVD SiO$_2$ shows a higher variation ranging from ~8-18%. The impact of ion energy between 89 MeV and 1.6 GeV on the size of the nanopores was also investigated for pores in PECVD SiO$_{2}$ and shows only negligible influence. These findings provide crucial insights for the controlled fabrication of conical nanopores in different materials, which is essential for optimizing membrane performance in applications that require precise pore geometry.

physics.app-ph↗

arXiv2024

Optical and spin properties of nitrogen vacancy centers formed along the tracks of high energy heavy ions

Exposure of matter to high energy, heavy ions induces defects along the trajectories of the ions through electronic and nuclear energy loss processes. Defects, including color centers, can recombine or form along latent damage tracks in many materials, such as insulators and semiconductors. Latent tracks in diamond were only recently observed. Here, we report on color center formation in diamond along the latent tracks of 1 GeV gold and uranium ions. Using depth-resolved photoluminescence, we observe direct formation of single vacancy related color centers (GR1-centers) along the ion tracks. Mobile vacancies can form NV-centers with native nitrogen atoms during thermal annealing. Molecular dynamics simulations show that isolated vacancies and vacancy clusters form through electronic stopping processes, leading to color center formation along ion trajectories from the sample surface to a depth of about 25 microns. We further report on the creation of individually isolated quasi-1D chains of NV-centers by using 1 GeV Au ions with a dilute fluence. The individual 1D NV-chains appear as isolated bright luminescence strings and present competitive electron spin properties compared to a background of NV-centers. Such spin textures can be explored as building blocks for applications in quantum information processing and quantum sensing.

quant-ph↗

arXiv2023

Annealing of swift heavy ion tracks in amorphous silicon dioxide

The annealing kinetics of the high energy ion damage in amorphous silicon dioxide (a-SiO2) are still not well understood, despite the material's widespread application in material science, physics, geology, and biology. This study investigates how annealing temperature, duration, and ambient environment affect the recovery of irradiation damage produced along the trajectory of swift heavy ions in a-SiO2. The track-annealing kinetics and the changing ion track morphology were investigated using synchrotron-based small-angle X-ray scattering (SAXS) and etching methods. We found that track annealing proceeds quicker near the sample surface demonstrated by a changing track etch rate as a function of depth. Measurements of ion tracks using SAXS show only small changes in the radial density distribution profile of the ion tracks. Activation energy of the annealing process at different sample depths was determined and the effect of the capping layer during the annealing process was also studied. Combination of oxygen diffusion and stress relaxation may contribute to the observed behaviour of preferential and anisotropic healing of the ion track. The results add to the fundamental understanding of ion track damage recovery and may have direct implications for materials for radioactive waste storage and solid state nanopores.

cond-mat.mtrl-sci↗

arXiv2021

Direct formation of nitrogen-vacancy centers in nitrogen doped diamond along the trajectories of swift heavy ions

We report depth-resolved photoluminescence measurements of nitrogen-vacancy (NV$^-$) centers formed along the tracks of swift heavy ions (SHIs) in type Ib synthetic single crystal diamonds that had been doped with 100 ppm nitrogen during crystal growth. Analysis of the spectra shows that NV$^-$ centers are formed preferentially within regions where electronic stopping processes dominate and not at the end of the ion range where elastic collisions lead to formation of vacancies and defects. Thermal annealing further increases NV yields after irradiation with SHIs preferentially in regions with high vacancy densities. NV centers formed along the tracks of single swift heavy ions can be isolated with lift-out techniques for explorations of color center qubits in quasi-1D registers with an average qubit spacing of a few nanometers and of order 100 color centers per micrometer along 10 to 30 micrometer long percolation chains.

cond-mat.mtrl-sci↗

arXiv2020

Fundamental Phenomena and Applications of Swift Heavy Ion Irradiations

This review concentrates on the specific properties and characteristics of damage structures generated with high-energy ions in the electronic energy loss regime. Irradiation experiments with so-called swift heavy ions (SHI) find applications in many different fields, with examples presented in ion-track nanotechnology, radiation hardness analysis of functional materials, and laboratory tests of cosmic radiation. The basics of the SHI-solid interaction are described with special attention to processes in the electronic subsystem. The broad spectrum of damage phenomena is exemplified for various materials and material classes, along with a description of typical characterization techniques. The review also presents state-of-the-art modeling efforts that try to account for the complexity of the coupled processes of the electronic and atomic subsystems. Finally, the relevance of SHI phenomena for effects induced by fission fragments in nuclear fuels and how this knowledge can be applied to better estimate damage risks in nuclear materials is discussed.

cond-mat.mtrl-sci↗

arXiv2019

Ionoacoustic detection of swift heavy ions

The maximum energy loss (Bragg peak) located near the end of range is a characteristic feature of ion stopping in matter, which generates an acoustic pulse, if ions are deposited into a medium in adequately short bunches. This so-called ionoacoustic effect has been studied for decades, mainly for astrophysical applications, and it has recently found renewed interest in proton therapy for precise range measurements in tissue. After detailed preparatory studies with 20 MeV protons at the MLL tandem accelerator, ionoacoustic range measurements were performed in water at the upgraded SIS18 synchrotron of GSI with 238U and 124Xe ion beams of energy about 300 MeV/u, and 12C ions of energy about 200 MeV/u using fast beam extraction to get 1 microsecond pulse lengths. Acoustic signals were recorded in axial geometry by standard piezo-based transducers at a 500 kHz mean frequency and evaluated in both the time and frequency domains. The resulting ranges for the different ions and energies were found to agree with Geant4 simulations as well as previous measurements to better than 1%. Given the high accuracy provided by ionoacoustic range measurements in water and their relative simplicity, we propose this new method for stopping power measurements for heavy ions at GeV energies and above. Our experimental results clearly demonstrate the potential of an ionoacoustic particle monitor especially for very intense heavy ion beams foreseen at future accelerator facilities.

nucl-ex↗

arXiv2017

Shrinking of Rapidly Evaporating Water Microdroplets Reveals their Extreme Supercooling

The fast evaporative cooling of micrometer-sized water droplets in vacuum offers the appealing possibility to investigate supercooled water - below the melting point but still a liquid - at temperatures far beyond the state-of-the-art. However, it is challenging to obtain a reliable value of the droplet temperature under such extreme experimental conditions. Here, the observation of morphology-dependent resonances in the Raman scattering from a stream of perfectly uniform water droplets has allowed us to measure with an absolute precision of better than 0.2% the variation in droplet size resulting from evaporative mass losses. This finding proved crucial to an unambiguous determination of the droplet temperature. In particular, a fraction of water droplets with initial diameter of 6379$\pm$12 nm were found to remain liquid down to 230.6$\pm$0.6 K. Our results question temperature estimates reported recently for larger supercooled water droplets, and provide valuable information on the hydrogen-bond network in liquid water in the hard-to-access deeply supercooled regime.

cond-mat.other↗

arXiv2012

Room temperature entanglement between distant single spins in diamond

Entanglement is the central yet fleeting phenomena of quantum physics. Once being considered a peculiar counter-intuitive property of quantum theory it has developed into the most central element of quantum technology providing speed up to quantum computers, a path towards long distance quantum cryptography and increased sensitivity in quantum metrology. Consequently, there have been a number of experimental demonstration of entanglement between photons, atoms, ions as well as solid state systems like spins or quantum dots, superconducting circuits and macroscopic diamond. Here we experimentally demonstrate entanglement between two engineered single solid state spin quantum bits (qubits) at ambient conditions. Photon emission of defect pairs reveals ground state spin correlation. Entanglement (fidelity = 0.67 \pm 0.04) is proven by quantum state tomography. Moreover, the lifetime of electron spin entanglement is extended to ms by entanglement swapping to nuclear spins, demonstrating nuclear spin entanglement over a length scale of 25 nm. The experiments mark an important step towards a scalable room temperature quantum device being of potential use in quantum information processing as well as metrology.

quant-ph↗

arXiv2012

Rectification properties of conically shaped nanopores: consequences of miniaturization

Nanopores attracted a great deal of scientific interest as templates for biological sensors as well as model systems to understand transport phenomena at the nanoscale. The experimental and theoretical analysis of nanopores has been so far focused on understanding the effect of the pore opening diameter on ionic transport. In this article we present systematic studies on the dependence of ion transport properties on the pore length. Particular attention was given to the effect of ion current rectification exhibited for conically shaped nanopores with homogeneous surface charges. We found that reducing the length of conically shaped nanopores significantly lowered their ability to rectify ion current. However, rectification properties of short pores can be enhanced by tailoring the surface charge and the shape of the narrow opening. Furthermore we analyze the relationship of the rectification behavior and ion selectivity for different pore lengths. All simulations were performed using MsSimPore, a software package for solving the Poisson-Nernst-Planck (PNP) equations. It is based on a novel finite element solver and allows for simulations up to surface charge densities of -2 e/nm^2. MsSimPore is based on 1D reduction of the PNP model, but allows for a direct treatment of the pore with bulk electrolyte reservoirs, a feature which was previously used in higher dimensional models only. MsSimPore includes these reservoirs in the calculations; a property especially important for short pores, where the ionic concentrations and the electric potential vary strongly inside the pore as well as in the regions next to pore entrance.

cond-mat.soft↗