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We present a first qualitative description of the atomic dynamics in two-dimensional (2D) materials induced by the impact of slow, highly charged ions. We employ a classical molecular dynamics simulation for the motion of the target atoms combined with a Monte Carlo model for the diffusive charge transport within the layer. Depending on the velocity of charge transfer (hopping time or hole mobility) and the number of extracted electrons which, in turn, depends on the charge state of the impinging ions, we find regions of stability of the 2D structure as well as parameter combinations for which nanopore formation due to Coulomb repulsion is predicted.

Experimental results on the charge-state-dependent sputtering of metallic gold nanoislands are presented. Irradiations with slow highly charged ions of metallic targets were previously considered to show no charge state dependent effects on ion-induced material modification, since these materials possess enough free electrons to dissipate the deposited potential energy before electron-phonon coupling can set in. By reducing the size of the target material down to the nanometer regime and thus enabling a geometric energy confinement, a possibility is demonstrated to erode metallic surfaces by charge state related effects in contrast to regular kinetic sputtering.

Aromatic self-assembled monolayers (SAMs) can be cross-linked into molecular nanosheets – carbon nanomembranes (CNMs) – via low-energy electron irradiation. Due to their favorable mechanical stability and tunable functional properties, they possess a high potential for various applications including nanosensors and separation membranes for osmosis or energy conversion devices. Despite this potential, the mechanistic details of the electron irradiation induced cross-linking process still need to be understood in more detail. Here, we studied the cross-linking of 4′-nitro-1,1′-biphenyl-4-thiol SAM on gold. The SAM samples were irradiated with different electron energies ranging from 2.5 to 100 eV in ultra-high vacuum and subsequently analysed by complementary techniques. We present results obtained via spectroscopy and microscopy characterization by high-resolution X-ray photoelectron spectroscopy (XPS), low-energy electron diffraction with micrometre sized electron beams (μLEED) and low-energy electron microscopy (LEEM). To demonstrate the formation of CNMs, the formed two-dimensional molecular materials were transferred onto grids and oxidized wafer and analyzed by optical, scanning electron microscopy (SEM) and atomic force microscopy (AFM). We found a strong energy dependence for the cross section for the cross-linking process, the rate of which decreases exponentially towards lower electron energies by about four orders of magnitude. We conduct a comparative analysis of the cross sections for the C–H bond scission via electron impact ionization and dissociative electron attachment and find that these different ionization mechanisms are responsible for the variation of the cross-linking cross section with electron energy.

The growing family of 2D materials led not long ago to combining different 2D layers and building artificial systems in the form of van der Waals heterostructures. Tailoring of heterostructure properties postgrowth would greatly benefit from a modification technique with a monolayer precision. However, appropriate techniques for material modification with this precision are still missing. To achieve such control, slow highly charged ions appear ideal as they carry high amounts of potential energy, which is released rapidly upon ion neutralization at the position of the ion. The resulting potential energy deposition is thus limited to just a few atomic layers (in contrast to the kinetic energy deposition). Here, we irradiated a freestanding van der Waals MoS2/graphene heterostructure with 1.3 keV/amu xenon ions in high charge states of 38, which led to nanometer-sized pores that appear only in the MoS2 facing the ion beam, but not in graphene beneath the hole. Reversing the stacking order leaves both layers undamaged, which we attribute to the high conductivity and carrier mobility in graphene acting as a shield for the MoS2 underneath. Our main focus is here on monolayer MoS2, but we also analyzed areas with few-layer structures and observed that the perforation is limited to the two topmost MoS2 layers, whereas deeper layers remain intact. Our results demonstrate that in addition to already being a valuable tool for materials processing, the usability of ion irradiation can be extended to mono- (or bi)layer manipulation of van der Waals heterostructures when the localized potential energy deposition of highly charged ions is also added to the toolbox.

Slow highly charged ions (HCI) were utilized successfully for the formation of various nanostructures in the surfaces of different materials. The creation mechanism of HCI-induced nanostructures was intensively studied in alkali- and alkaline-earth fluorides. Here, we are investigating another type of fluorine-containing ionic crystals of different crystalline and electronic structure, namely lanthanum fluoride, LaF3. The single crystals were irradiated with slow (eV-keV) highly charged xenon ions from an Electron Beam Ion Trap. After irradiation, the crystals surfaces were investigated by scanning force microscopy. The measured topographic images show nanohillocks emerging from the surface. These nanostructures were observed only after exceeding a well-defined threshold in the potential energy. The role of ion parameters for nanohillocks formation as well as a comparison with results for swift heavy ion irradiations of LaF3 single crystals are presented. Furthermore, the similarities and differences between LaF3 and other ionic fluoride crystals, in the creation of surface nanostructures, are discussed.

The scattering of ions in solids is accompanied with momentum transfer and electronic excitations resulting in the slowing down of the ion. The amount of energy transferred in a single scattering event depends on the particular trajectory which can be traced back through the scattering angle. Performing scattering angle dependent measurements of slow highly charged Xe ions transmitted through freestanding single-, bi-, and trilayer graphene allows us to determine the charge exchange and energy loss for different minimal interatomic distances. Interestingly, the charge exchange shows an increase with scattering angle by a factor of less than 2, while the energy loss increases by more than a factor of 10 for ${3}^{\phantom{\rule{0.16em}{0ex}}\ensuremath{\circ}}$ compared to forward direction. Our results can be compared to a time-dependent potential model and show that determination of the stopping cross section is not straightforward even with angle-dependent data at hand.

The formation of nanopores by highly charged ion impacts on freestanding fluorine-functionalized graphene is demonstrated. The process is driven by potential sputtering, which becomes active by changing the semimetallic property of graphene into a strongly insulating state by fluorination. The interaction of fluorographene with highly charged ions is also studied in terms of charge exchange and kinetic energy loss. A higher number of captured electrons and a larger kinetic energy loss than in pristine graphene are observed, which can be well explained by an increase in the ion neutralization length and in the atomic areal density of the target, respectively. Using a computer code based on a time-dependent scattering potential model, a connection between the efficiency of charge exchange and the fluorine coverage is revealed. Our results suggest a competition of two distinct nanostructure formation processes, leading either to pore formation or fluorine desorption.

Defects engineering plays a central role in manipulating the electronic, optical and structure properties of materials and for device fabrication. The authors propose and experimentally verify a method to use ion beams for defect engineering of 2D materials based on a time dependent interatomic potential.

Porous single layer molybdenum disulfide (MoS$_2$) is a promising material for applications such as DNA sequencing and water desalination. In this work, we introduce irradiation with highly charged ions (HCIs) as a new technique to fabricate well-defined pores in MoS$_2$. Surprisingly, we find a linear increase of the pore creation efficiency over a broad range of potential energies. Comparison to atomistic simulations reveals the critical role of energy deposition from the ion to the material through electronic excitation in the defect creation process, and suggests an enrichment in molybdenum in the vicinity of the pore edges at least for ions with low potential energies. Analysis of the irradiated samples with atomic resolution scanning transmission electron microscopy reveals a clear dependence of the pore size on the potential energy of the projectiles, establishing irradiation with highly charged ions as an effective method to create pores with narrow size distributions and radii between ca. 0.3 and 3 nm., 22 pages, 4 figures

We present a direct way to generate hillock-like nanostructures on CaF

Einleitung: Der Einfluss von Stress während der Schwangerschaft auf den Fetus lässt sich auch postnatal bis in das Erwachsenenalter und teilweise sogar bis in nachfolgende Generationen nachweisen. Eine Vielzahl an Störgrößen erschwert es enorm, beim Menschen konkrete Kausalitäten auszuarbeiten. Mit dem Weißbüschelaffen steht ein humanrelevanter Modellorganismus zur Verfügung, der eine dem Menschen sehr ähnliche Situation in Bezug auf die Physiologie der Trächtigkeit sowie der männlichen Reproduktion bietet, gleichzeitig jedoch einen hohen Grad der Standardisierung ermöglicht. Ziele der Untersuchungen: Im Rahmen der vorliegenden Arbeit sollten ausgewählte Faktoren des Reproduktionssystems in den Hoden adulter Weißbüschelaffen mittels qPCR und Immunhistochemie nachgewiesen und auf Zellebene lokalisiert werden. Weiterhin sollte ermittelt werden, ob die nachgewiesenen Proteine durch pränatalen Stress beeinflusst werden. Ziel des zweiten Teils der vorliegenden Arbeit war es herauszufinden, ob und in welcher Form sich ein standardisierter pränataler Stressreiz postnatal auf ausgewählte Parameter der männlichen Reproduktion des Weißbüschelaffen bis hin zur F3-Generation auswirken kann. Tiere, Material und Methoden: Trächtige Weißbüschelaffen wurden von Trächtigkeitstag 42 bis 48 (EDEX) bzw. Trächtigkeitstag 90 bis 96 (LDEX) täglich mit 5 mg Dexamethason (DEX) pro kg Körpergewicht per os behandelt. Eine Kontrollgruppe (C) erhielt während der gesamten Trächtigkeit keine Glucocorticoide. Von den adulten männlichen Nachkommen der F1-Generation wurden 9 (C), 8 (EDEX) und 9 (LDEX) jeweils tiefgefrorene Hoden auf 12 Transkripte aus den Gruppen der Enzyme der Steroidbiosynthese, der Steroidrezeptoren, des Relaxinsystems und der Proliferationsmarker mittels qPCR quantitativ untersucht. Die jeweils kontralateralen Hoden waren in Paraformaldehyd fixiert worden und wurden parallel auf Proteinebene mittels Immunhistochemie (IHC) untersucht. Für den zweiten Teil der vorliegenden Arbeit wurden die jeweils in maternaler Linie weitergezüchteten Männchen der DEX F2 (n = 2) und DEX F3 (n = 3) auf relevante Parameter der Reproduktionsfähigkeit hin untersucht: Die Größe der Hoden wurde im Frühling, im Sommer und im Winter gemessen, Blutplasma¬proben an einem Tag im Sommer um 8 Uhr, 12 Uhr und 16 Uhr sowie an einem Tag im Winter um 8 Uhr entnommen und daraus mittels ELISA die Konzentration von Testosteron sowie teilweise von 17β Östradiol ermittelt; Ejakulate wurden durch penile Vibrostimulation (PVS) gewonnen und computergestützt untersucht. Alle Ergebnisse wurden jeweils mit mindestens elf unbehandelten männlichen Tieren derselben Kolonie verglichen. Ergebnisse: Alle untersuchten für die männliche Reproduktion relevanten Proteine konnten in den Hoden der F1 nachgewiesen werden. In den Hoden der EDEX F1 und der LDEX F1 war auf Proteinebene jeweils einzig die Steroid-5α-Reduktase 1 (SRD5A1) gegenüber C erhöht. Auf Genebene waren von den untersuchten Transkripten nur in den Hoden der EDEX F1 die SRD5A1, SRD5A2 und Ki 67 jeweils signifikant gegenüber C aufreguliert. Die Hodengröße änderte sich nicht signifikant im Jahresverlauf. Im Tagesverlauf konnte ein signifikanter Anstieg der Testosteronkonzentration im Blutplasma zwischen 8 Uhr und 12 Uhr ermittelt werden. Jedoch konnte kein signifikanter Unterschied zwischen Testosteronkonzentration im weiteren Tageszeitenvergleich, im Sommer und Winter und in Relation zum Alter festgestellt werden. Darüber hinaus bestand keine Korrelation zwischen Testosteron- und 17β Östradiol¬konzentration aus denselben Blutproben. Der Vergleich aller im Zusammenhang mit der PVS erhobenen Parameter zwischen DEX F2/F3 und C ergab, dass einzig die Erfolgsrate der PVS in DEX F2/F3 niedriger lag als in C. Der versuchsgruppen-übergreifende Vergleich aller Ejakulate zwischen den Altersgruppen ergab bei jung adulten Tieren einen signifikant höheren Anteil an motilen Spermien sowie eine signifikant schlechtere Erfolgsrate der PVS gegenüber adulten Tieren. Schlussfolgerungen: Die Ergebnisse der vorliegenden Arbeit geben Hinweise darauf, wie sich Stress während der Trächtigkeit beim Weißbüschelaffen auf die Nachkommen auswirken könnte: In DEX F1 sind wichtige Voraussetzungen für eine funktionierende Testosteron-Biosynthese sowie die Vermittlung von Testosteron- und Östrogen-mediierten Signalen im Hoden gegeben, möglicherweise sogar in verstärkter Weise. Darüber hinaus bestätigen diese Ergebnisse die Humanrelevanz des Weißbüschelaffen als Modell¬organismus zum männlichen Reproduktionssystem. In DEX F2/F3 könnte die niedrige Erfolgsrate der PVS ein Hinweis auf verminderte Konzentrationsfähigkeit in den auf intra¬uterinen Stress folgenden Generationen sein. Jedoch unterscheiden sich die meisten erhobenen reproduktions-physiologisch bedeutsamen Parameter nicht zwischen DEX F2/F3 und C.:1 EINLEITUNG 2 LITERATURÜBERSICHT 2.1 Glucocorticoide und Stress während der Trächtigkeit 2.2 Relevante Hormone der Reproduktion und ihre Biosynthese 2.2.1 3β-Hydroxysteroid-Dehydrogenase 2 2.2.2 Testosteron und Androgenrezeptor 2.2.3 Steroid-5α-Reduktasen 2.2.4 Aromatase 2.2.5 17β-Hydroxysteroid-Dehydrogenase 7 2.2.6 Östradiol und Östrogenrezeptoren 2.2.7 Relaxinsystem 2.2.8 Proliferationsfaktoren 2.3 Weißbüschelaffen 2.3.1 Allgemeines zu Weißbüschelaffen 2.3.2 Reproduktionsbiologie der männlichen Weißbüschelaffen 3 TIERE, MATERIAL UND METHODEN 3.1 Versuchsteil I – ex vivo Hoden DEX F1 3.1.1 Versuchsaufbau (DEX) im DPZ 3.1.2 qPCR an DEX F1 Hoden 3.1.3 Immunhistochemie an Hoden der DEX F1 3.2 Versuchsteil II – in vivo DEX F2/DEX F3 3.2.1 Herkunft der Weißbüschelaffen 3.2.2 Haltung der Weißbüschelaffen 3.2.3 Bestimmung der Hodengrößen und des Körpergewichtes 3.2.4 Blutentnahmen und Hormonbestimmungen mittels ELISA 3.2.5 Penile Vibrostimulation 3.3 Statistische Auswertung 4 ERGEBNISSE 4.1 Versuchsteil I – ex vivo Hoden DEX F1 4.1.1 qPCR der Hoden der F1 4.1.2 Immunhistochemie der Hoden der DEX F1 4.1.2.1 Enzyme der Steroidbiosynthese 4.1.2.2 Steroidrezeptoren 4.1.2.3 Relaxinsystem 4.1.2.4 Proliferationsmarker 4.1.3 Zusammenfassung der Ergebnisse des Versuchsteils I – ex vivo DEX F1 4.2 Versuchsteil II – in vivo DEX F2/F3 4.2.1 Hodengrößen 4.2.2 Testosteron 4.2.3 Ejakulatanalyse 4.2.4 Zusammenfassung der Ergebnisse des Versuchsteils II – in vivo DEX F2/F3 5 DISKUSSION 5.1 Versuchsteil I – ex vivo Hoden DEX F1 5.1.1 Vergleichende Diskussion der Ergebnisse auf Gen- und Proteinebene in den Hoden der F1 5.1.1.1 Relevante Enzyme der Testosteronbiosynthese 5.1.1.2 Steroidrezeptoren 5.1.1.3 Das Relaxinsystem 5.1.1.4 Proliferationsfaktoren 5.2 Versuchsteil II – in vivo DEX F2/F3 5.2.1 Hodengrößen 5.2.2 Testosteron 5.2.3 Ejakulatanalyse 5.3 Schlussbetrachtung 6 ZUSAMMENFASSUNG 7 SUMMARY 8 Literaturverzeichnis 9 ANHANG 10 DANKSAGUNG Introduction: The impact of prenatal stress can also be detected in the grown-up offspring and partly even in following generations. There are many interfering variables that make it nearly impossible to establish precise correlations in humans. However, the common marmoset is a model organism very similar to humans with respect to the physiology of pregnancy as well as to male reproduction. In addition to that, the possibility of a high-grade standardisation is extremely advantageous. Objective: The first part of this work aimed at detecting selected factors of the reproductive system in testes of adult common marmosets by qPCR and immunohistochemistry, and localising them at the cellular level; both were directed at clarifying whether or not the target proteins respond to prenatal stress. The second part aimed at determining in which form and to what extent standardised prenatal stress affects selected parameters of male reproduction up to the F3-generation in the common marmoset. Animals, materials and methods: Pregnant common marmosets were treated daily with a dose of 5 mg dexamethasone (DEX) per kg body weight per os on gestational days 42 to 48 (EDEX) and gestational days 90 to 96 (LDEX). A control group (C) received no glucocorticoid treatment during pregnancy at all. By qPCR, 12 transcripts from the groups of steroidogenic enzymes, steroid receptors, the relaxin system and the proliferation markers were quantitatively analysed in 9 (C), 8 (EDEX) und 9 (LDEX) frozen testes of F1 generation adult male offspring. Respective contralateral testes had been fixed in paraformaldehyde and were analysed on protein level by immunohistochemistry (IHC). In the second part of this work, males of DEX F2 (n = 2) and DEX F3 (n = 3), each bred in the maternal line, were analysed for relevant parameters of reproduction ability: testes were measured in spring, summer, and winter; blood plasma samples were taken on one day in summer at 8 a.m., 12 noon and 4 p.m. as well as on a day in winter at 8 a.m. and subsequently analysed by ELISA for testosterone and partly 17β oestradiol; ejaculates have been gathered by penile vibrostimulation (PVS) and were tested by computer-assisted sperm analysis. All results were compared with those on at least 11 untreated male common marmosets of the same colony. Results: Each of the targeted proteins relevant for male reproduction was detected in testes of F1. At the protein level only steroid 5α-reductase 1 (SRD5A1) was enhanced expressed in testes of EDEX F1, and LDEX F1 compared to C. At the gene level, SRD5A1, SRD5A2 and Ki 67 were each enhanced expressed compared to C, but in testes of EDEX F1 only. Testis size did not vary significantly during the course of the year. During the course of the day there was a significant rise of the testosterone concentration in blood plasma between 8 a.m. and 12 noon. However, there was no significant difference in the testosterone concentration during other times of the day, nor between summer and winter or in relation to the age of the monkeys. Furthermore there was no correlation between the testosterone and the 17β oestradiol concentrations in the same blood samples. Comparisons of all measured PVS parameters between DEX F2/F3 and C gave a lower success rate of PVS in DEX F2/F3 as the only difference. Comparisons of the ejaculates between age groups irrespective of the DEX classification revealed that young adult common marmosets possess a significantly higher percentage of motile sperms as well as a significantly lower success rate of PVS compared to adult monkeys. Conclusions: The results of this study suggest how stress during pregnancy could influence subsequent generations in the common marmoset: in DEX F1, important requirements of active testosterone biosynthesis as well as of mediation of testosterone and oestrogen signals in testis are met, possibly even enhanced. In addition, these results confirm the relevance of the common marmoset as a model organism for human male reproduction. In DEX F2/F3, the low success rate of PVS might indicate a reduced capability to concentrate in generations following intrauterine stress on F1. Yet, most of the tested parameters pertinent to reproduction physiology do not differ between DEX F2/F3 and C.:1 EINLEITUNG 2 LITERATURÜBERSICHT 2.1 Glucocorticoide und Stress während der Trächtigkeit 2.2 Relevante Hormone der Reproduktion und ihre Biosynthese 2.2.1 3β-Hydroxysteroid-Dehydrogenase 2 2.2.2 Testosteron und Androgenrezeptor 2.2.3 Steroid-5α-Reduktasen 2.2.4 Aromatase 2.2.5 17β-Hydroxysteroid-Dehydrogenase 7 2.2.6 Östradiol und Östrogenrezeptoren 2.2.7 Relaxinsystem 2.2.8 Proliferationsfaktoren 2.3 Weißbüschelaffen 2.3.1 Allgemeines zu Weißbüschelaffen 2.3.2 Reproduktionsbiologie der männlichen Weißbüschelaffen 3 TIERE, MATERIAL UND METHODEN 3.1 Versuchsteil I – ex vivo Hoden DEX F1 3.1.1 Versuchsaufbau (DEX) im DPZ 3.1.2 qPCR an DEX F1 Hoden 3.1.3 Immunhistochemie an Hoden der DEX F1 3.2 Versuchsteil II – in vivo DEX F2/DEX F3 3.2.1 Herkunft der Weißbüschelaffen 3.2.2 Haltung der Weißbüschelaffen 3.2.3 Bestimmung der Hodengrößen und des Körpergewichtes 3.2.4 Blutentnahmen und Hormonbestimmungen mittels ELISA 3.2.5 Penile Vibrostimulation 3.3 Statistische Auswertung 4 ERGEBNISSE 4.1 Versuchsteil I – ex vivo Hoden DEX F1 4.1.1 qPCR der Hoden der F1 4.1.2 Immunhistochemie der Hoden der DEX F1 4.1.2.1 Enzyme der Steroidbiosynthese 4.1.2.2 Steroidrezeptoren 4.1.2.3 Relaxinsystem 4.1.2.4 Proliferationsmarker 4.1.3 Zusammenfassung der Ergebnisse des Versuchsteils I – ex vivo DEX F1 4.2 Versuchsteil II – in vivo DEX F2/F3 4.2.1 Hodengrößen 4.2.2 Testosteron 4.2.3 Ejakulatanalyse 4.2.4 Zusammenfassung der Ergebnisse des Versuchsteils II – in vivo DEX F2/F3 5 DISKUSSION 5.1 Versuchsteil I – ex vivo Hoden DEX F1 5.1.1 Vergleichende Diskussion der Ergebnisse auf Gen- und Proteinebene in den Hoden der F1 5.1.1.1 Relevante Enzyme der Testosteronbiosynthese 5.1.1.2 Steroidrezeptoren 5.1.1.3 Das Relaxinsystem 5.1.1.4 Proliferationsfaktoren 5.2 Versuchsteil II – in vivo DEX F2/F3 5.2.1 Hodengrößen 5.2.2 Testosteron 5.2.3 Ejakulatanalyse 5.3 Schlussbetrachtung 6 ZUSAMMENFASSUNG 7 SUMMARY 8 Literaturverzeichnis 9 ANHANG 10 DANKSAGUNG

Over seventy years ago, Niels Bohr described how the charge state of an atomic ion moving through a solid changes dynamically as a result of electron capture and loss processes, eventually resulting in an equilibrium charge state. Although obvious, this process has so far eluded direct experimental observation. By peeling a solid, such as graphite, layer by layer, and studying the transmission of highly charged ions through single-, bi- and trilayer graphene, we can now observe dynamical changes in ion charge states with monolayer precision. In addition we present a first-principles approach based on the virtual photon model for interparticle energy transfer to corroborate our findings. Our model that uses a Gaussian shaped dynamic polarisability rather than a spatial delta function is a major step in providing a self-consistent description for interparticle de-excitation processes at the limit of small separations. Ion-solid interactions are governed by a range of complex processes the direct experimental observation of which pose their own set of challenges. Here, the authors present a joint experimental and first-principles approach to study and describe the underlying mechanism of electron capture for an ion travelling through layers of graphene with monolayer precision.

As surface-only materials, freestanding 2D materials are known to have a high level of contamination—mostly in the form of hydrocarbons, water, and residuals from production and exfoliation. For well-designed experiments, it is of particular importance to develop effective clean- ing procedures, especially since standard surface science techniques are typically not applicable. We perform ion spectroscopy with highly charged ions transmitted through freestanding atomically thin materials and present two techniques to achieve clean samples, both based on thermal treatment. Ion charge exchange and energy loss are used to analyze the degree of sample contamination. We find that even after cleaning, heavily contaminated spots remain on single layer graphene. The contamination coverage, however, clusters in strand-like structures leaving large clean areas. We present a way to discriminate clean from contaminated areas with our ion beam spectroscopy if the heterogeneity of the surface is increased sufficiently enough. We expect a similar discrimination to be necessary in most other experimental techniques.

Synopsis Recent experiments found that the neutralisation of highly charged ions interacting with a freestanding single layer of graphene proceeds on a femtosecond time scale. This ultra-fast deexcitation was attributed to Interatomic Coulombic Decay (ICD), a process in which core holes in the projectile are filled by previously captured outer electrons and the energy is transferred to electrons of the surrounding carbon atoms. ICD therefore predicts the emission of many low energy electrons. We now present experimental evidence that e.g. Xe40+ indeed emits up to 85 electrons with energies below 20 eV.

Synopsis Highly charged ions (HCIs) are an efficient tool for the perforation of suspended 2D materials. Only a fraction of their potential energy is transferred to the atomically thin target during the very short interaction time and is available for pore formation. Charge exchange spectra were measured for highly charged xenon ions transmitted through suspended, single layer MoS2 in order to determine the deposited potential energy available for pore formation. Additionally, charge exchange dependent ion stopping responsible for kinetic sputtering was measured simultaneously.

He-induced nanostructured tungsten (so-called W-fuzz) was bombarded with Ar ions under 60° and the dynamic erosion behaviour was experimentally investigated. By using a highly sensitive quartz-crystal-microbalance technique in a particle catcher configuration, the sputtered particles distribution of W-fuzz could be evaluated. In contrast to a flat sample, where sputtered particles are emitted primarily in forward direction, we find that W-fuzz samples emit sputtered particles preferably in backward direction (i.e. in the direction of the incident ion beam). After continuous Ar irradiation of a W-fuzz sample the distribution approaches that of a flat sample. In addition to experimental data we also show modelling results obtained with a state-of-the-art Monte-Carlo (MC) binary collision approximation (BCA) code TRI3DYN in full 3D. Surface morphology changes as monitored by SEM as well as the dynamic sputtering behaviour can be well reproduced by the full 3D MC-BCA code.

An improved quartz crystal microbalance measurement method is described, which allows us to determine erosion, implantation, and release rates of thin films, during changing temperatures and up to 700 K. A quasi-simultaneous excitation of two eigenmodes of the quartz resonator is able to compensate for frequency drifts due to temperature changes. The necessary electronics, the controlling behavior, and the dual-mode temperature compensation are described. With this improved technique, quantitative in situ temperature-programmed desorption measurements are possible and the quartz crystal microbalance can be used for quantification of thermal desorption spectroscopy measurements with a quadrupole mass spectrometer. This is demonstrated by a study of the retention and release behavior of hydrogen isotopes in fusion-relevant materials. We find that more than 90% of the deuterium implanted into a thin film of beryllium is released during a subsequent temperature ramp up to 500 K.

X-ray emission of slow (

The roughness of a surface is known to have a strong influence on the sputtering process. Commonly used 1D Monte Carlo codes for calculating sputter yields show good agreement with experimental data only for comparably flat surfaces, whereas local ion incidence angles, shadowing and redeposition influence the sputter yields in both magnitude and angular dependence on rough surfaces. In the present work, we therefore investigated tungsten samples of largely different roughness, characterised by atomic force and confocal microscopy. A highly sensitive quartz crystal microbalance was used to determine sputter yields during ion irradiation. Low ion fluences were applied to ensure that the surface morphology did not change during irradiation. The results were used to benchmark our new ray-tracing simulation code SPRAY, which can take microscopy images without limitations in size as input. SPRAY was furthermore applied to perform systematic simulations for artificially roughened and computer-generated surfaces. A clear result was that the governing parameter for description of the sputtering behaviour is the mean value of the surface inclination angle distribution, rather than the commonly used root mean square roughness. Our simulations show that this parameter is universally applicable for a wide range of different surface structures.

We publish three Roadmaps on photonic, electronic and atomic collision physics in order to celebrate the 60th anniversary of the ICPEAC conference. Roadmap III focusses on heavy particles: with zero to relativistic speeds. Modern theoretical and experimental approaches provide detailed insight into the wide range of many-body interactions involving projectiles and targets of varying complexity ranging from simple atoms, through molecules and clusters, complex biomolecules and nanoparticles to surfaces and crystals. These developments have been driven by technological progress and future developments will expand the horizon of the systems that can be studied. This Roadmap aims at looking back along the road, explaining the evolution of the field, and looking forward, collecting nineteen contributions from leading scientists in the field., Journal of Physics B: Atomic, Molecular and Optical Physics, 52 (17), ISSN:1361-6455, ISSN:0368-3508, ISSN:0953-4075, ISSN:0022-3700

GaP single crystals were irradiated with slow highly charged ions (HCI) using 114 keV 129Xe(33–40)+ and with various swift heavy ions (SHI) of 30 MeV I9+ and 374 MeV–2.2 GeV 197Au25+. The irradiated surfaces were investigated by scanning force microscopy (SFM). The irradiations with SHI lead to nanohillocks protruding from the GaP surfaces, whereas no changes of the surface topography were observed after the irradiation with HCI. This result indicates that a potential energy above 38.5 keV is required for surface nanostructuring of GaP. In addition, strong coloration of the GaP crystals was observed after irradiation with SHI. The effect was stronger for higher energies. This was confirmed by measuring an increased extinction coefficient in the visible light region.

In the context of recent efforts to combine high Mn concentrations in (Ga,Mn)N with a pronounced p-type carrier density, (Ga,Mn)N/GaN:Mg-superlattices have been fabricated using plasma-assisted molecular beam epitaxy. Profiles of the dopant atomic densities in the heterostructures are obtained by secondary ion mass spectroscopy. They show an abrupt drop of two to three orders of magnitude in both Mn and Mg concentrations after the first GaN:Mg layer above a critical Mg-flux. Scanning electron microscopy before and after selective etching reveals a polarity inversion from originally Ga-face to N-face GaN in samples in which high Mg fluxes were applied. From our observations, we are able to draw an analogy between the impurity incorporation laws of Mg and Mn.

This paper reports on the importance of crystallographic cuts with a different orientation on the luminescent properties and structural changes of Al2O3 implanted with Er+ ions at 190 keV and with a fluence of 1.0 × 1016 cm−2. Post-implantation annealing at 1000 °C in oxygen atmosphere was also done. The chemical compositions and erbium concentration-depth profiles of implanted layers were studied by Rutherford Backscattering Spectrometry (RBS) and compared to SRIM simulations. The same value of the maximum erbium concentration (up to 2 at.%) was observed at a depth of about 40 nm for all crystallographic cuts. The structural properties of the prepared layers were characterised by RBS/channelling. The relative amount of disordered atoms of 70–80% was observed in the prepared implanted layers and discussed for various cuts. It has been found that erbium is positioned randomly in the Al2O3 crystalline matrix, and no preferential positions appeared even after the annealing procedure. Erbium luminescence properties were measured in the wavelength range of 1440–1650 nm for all samples. As-implanted Al2O3 samples had a significant luminescence band at 1530 nm. The best luminescence was repeatedly observed in the 〈0 0 0 1〉 cut of Al2O3. The annealing procedure significantly improved the luminescent properties.

The interaction of ions with solid materials may lead to charge exchange. Previous results show that charge exchange is confined to the uppermost surface layers of a solid or to the thickness of a freestanding 2D material, even when initially highly charged ions are used. Several processes are active during charge exchange and a clear distance or impact parameter dependence is observed. Here I show, that highly charged ion transmission can be used to determine the material structure of 2D materials especially when atomically resolved electron microscopy cannot be applied. The method is based on measurement of energy-, charge-, and angle-resolved ion transmission spectra in coincidence and a comparison with a local model for a time-dependent change in the projectile’s electron occupation and consequently the scattering potential. Also necessary experimental procedures are discussed.

We present an ultrahigh vacuum setup for ion spectroscopy of freestanding two-dimensional solid targets. An ion beam of different ion species (e.g., Xe with charge states from 1 to 44 and Ar with charge states from 1 to 18) and kinetic energies ranging from a few 10 eV to 400 keV is produced in an electron beam ion source. Ions are detected after their transmission through the 2D target with a position sensitive microchannel plate detector allowing the determination of the ion’s exit charge state as well as the scattering angle with a resolution of approximately 0.04°. Furthermore, the spectrometer is mounted on a swiveling frame covering a scattering angle of ±8° with respect to the incoming beam direction. By utilizing a beam chopper, we measure the time-of-flight of the projectiles and determine the energy loss when passing a 2D target with an energy uncertainty of about 2%. Additional detectors are mounted close to the target to observe emitted secondary particles and are read-out in coincidence with the position and time information of the ion detector. A signal in these detectors can also be used as a start trigger for time-of-flight measurements, which then yield an energy resolution of 1% and an approximately 1000-fold larger duty cycle. First results on the interaction of slow Xe30+ ions with a freestanding single layer of graphene obtained with the new setup are compared to recently published data where charge exchange and energy were measured by means of an electrostatic analyzer.

A polystyrene film spun onto polished silicon substrates was implanted with argon ions using plasma immersion ion implantation (PIII) to activate its surface for single-step immobilization of biological molecules. The film was subsequently investigated by X-ray and neutron reflectometry, ultraviolet (UV)–visible (vis) and Fourier transform infrared (FTIR) ellipsometry, FTIR and Raman spectroscopy, as well as nuclear reaction analysis to determine the structural and compositional transformations associated with the surface activation. The ion irradiation resulted in a significant densification of the carbon structure, which was accompanied by hydrogen loss. The density and hydrogen profiles in the modified surface layers were found to agree with the expected depths of ion implantation as calculated by the Stopping and Range of Ions in Matter (SRIM) software. The data demonstrate that the reduction in film thickness is due to ion-induced densification rather than the removal of material by etching. Characte...

The implantations were performed in 4H silicon carbide homoepitaxial layers deposited on (00.1) substrates with 8° offcut, and reference 4H-SiC substrates. The 2 MeV Se+ ions and 1 MeV Al+ ions were implanted with four fluences subsequently increased by the factor of 4–5×. The samples were studied by means of X-ray diffraction topography, high-resolution diffractometry, specular X-ray reflectometry, and Rutherford backscattering spectrometry\channeling method. The dislocation density in the samples evaluated from the diffraction topographs did not exceed 5 × 103 cm−2. The representative roughness values evaluated from the reflectometric measurements was 2.3 ± 0.1 nm for the substrates and less than 1.4 ± 0.1 nm for the epitaxial layers. A significantly higher damage level in the case of 2 MeV Se+ ions in comparison with 1 MeV Al+ ion and a linear increase of the strain with the fluence was indicated, but the highest doses of selenium ions caused the amorphization of the implanted layer. It was also possible to obtain a good fitting of the theoretical and experimental diffraction curves approximating the strain profiles by the distribution of the point defects calculated with the SRIM 2008 code. It was confirmed that the maximum coming from surface damages observed in channeling spectra of the virgin substrate wafers was significantly higher than in the case of epitaxial layers. Copyright © 2015 John Wiley & Sons, Ltd.

International audience; Conditions for ion track formation in single crystal SrTiO3 and TiO2 (rutile) after irradiations using swift heavy ion beams with specific energies below 1 MeV/amu were investigated in this work. Rutherford backscattering spectroscopy in channeling was used to measure ion tracks in the bulk, while atomic force microscopy was used for observation of ion tracks on the surfaces. Variations in the ion track sizes and respective thresholds were observed after irradiations under random, channeling and near-channeling conditions close to normal incidence. These variations are attributed to the specifics of the electronic stopping power of swift heavy ions under the investigated conditions. In the case of ion channeling, electronic stopping power is reduced and observed ion tracks are smaller. The opposite was found under the near-channeling conditions when lowering of the ion track formation threshold was observed. We attribute this finding to the oscillating electronic stopping power with large peak values. For both materials, thresholds for bulk and surface ion track formation were found to be surprisingly close, around 10 keV nm−1. Obtained results are compared with predictions of the analytical thermal spike model.

The impact of highly charged ions onto a solid gives rise to charge exchange between the ions and target atoms, so that slow ions get neutralized in the vicinity of the surface. Using highly charged Ar and Xe ions and the surface-only material graphene as a target, we show that the neutralization and de-excitation of the ions proceeds on a sub-10 fs time scale. We further demonstrate that a multiple interatomic coulombic decay (ICD) model of highly charged ions can describe the observed ultrafast de-excitation. Other de-excitation mechanisms involving non-radiative decay and quasi- molecular orbitals formation during the impact are not important, as follows from the comparison of our experimental data with the results of first-principles calculations. Our method also enables the estimation of ICD rates directly.

We report on charge exchange and energy loss measurements for slow highly charged Xeq+ (q ≤ 35) ions after transmission through a single layer of freestanding graphene. Surprisingly short charge equilibration times of only a few femtoseconds are found, which cannot be explained within currently available models. OA gold

The structural and magnetic properties of ZnO (0 0 0 1) single crystals implanted with 200 keV Gd ions up to a fluence of 5 × 10 15 cm −2 and subsequently annealed at 800 °C in various atmospheres were studied. The chemical composition and concentration depth profiles of ion-implanted layers were characterised by Rutherford Back-Scattering spectrometry (RBS) and compared to SRIM simulations. The as-implanted Gd depth profiles were found to be broader than those simulated by SRIM, but the projected range coincided well with that simulated. After annealing at 800 °C, the depth profiles became narrower. The structural changes in the layers modified by ion implantation and subsequent annealing were characterised by RBS channelling. The annealing led to partial recrystallisation and a decrease in the number of Gd atoms situated in substitutional positions. Raman spectroscopy showed that the point defects in Zn and O vacancies had been created by implantation and that these defects are most effectively cured after annealing in oxygen atmosphere. AFM analysis was used to determine the surface-morphology changes after the implantation and annealing procedures. The as-implanted samples exhibited ferromagnetism persisting up to room temperature. The annealing procedure led to paramagnetic behaviour, probably caused by the formation of gadolinium clusters.