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There is an urgent need to increase the global data storage capacity, as current approaches lag behind the exponential growth of data generation driven by the Internet, social media and cloud technologies. In addition to increasing storage density, new solutions should provide long-term data archiving that goes far beyond traditional magnetic memory, optical disks and solid-state drives. We propose a concept of energy-efficient, ultralong, high-density data archiving based on optically active atomic-size defects in a radiation resistance material, silicon carbide (SiC) [1]. The information is written in these defects by focused ion beams and read using photoluminescence or cathodoluminescence. The temperature-dependent deactivation of these defects suggests a retention time minimum over a few generations under ambient conditions. With near-infrared laser excitation, grayscale encoding and multi-layer data storage, the areal density corresponds to that of Blu-ray discs. Furthermore, we demonstrate that the areal density limitation of conventional optical data storage media due to the light diffraction can be overcome by focused electron-beam excitation.

There is an urgent need to increase the global data storage capacity, as current approaches lag behind the exponential growth of data generation driven by the Internet, social media and cloud technologies. In addition to increasing storage density, new solutions should provide long-term data archiving that goes far beyond traditional magnetic memory, optical disks and solid-state drives. Here, we propose a concept of energy-efficient, ultralong, high-density data archiving based on optically active atomic-size defects in a radiation resistance material, silicon carbide (SiC). The information is written in these defects by focused ion beams and read using photoluminescence or cathodoluminescence. The temperature-dependent deactivation of these defects suggests a retention time minimum over a few generations under ambient conditions. With near-infrared laser excitation, grayscale encoding and multi-layer data storage, the areal density corresponds to that of Blu-ray discs. Furthermore, we demonstrate that the areal density limitation of conventional optical data storage media due to the light diffraction can be overcome by focused electron-beam excitation.

Experimental data in OriginPro

We investigate the morphologies of the Ge(001) surface that are produced by bombardment with a normally incident, broad argon ion beam at sample temperatures above the recrystallization temperature. Two previously-observed kinds of topographies are seen, i.e., patterns consisting of upright and inverted rectangular pyramids, as well as patterns composed of shallow, isotropic basins. In addition, we observe the formation of an unexpected third type of pattern for intermediate values of the temperature, ion energy and ion flux. In this type of intermediate morphology, isolated peaks with rectangular cross sections stand above a landscape of shallow, rounded basins. We also extend past theoretical work to include a second order correction term that comes from the curvature dependence of the sputter yield. For a range of parameter values, the resulting continuum model of the surface dynamics produces patterns that are remarkably similar to the intermediate morphologies we observe in our experiments. The formation of the isolated peaks is the result of a term that is not ordinarily included in the equation of motion, a second order correction to the curvature dependence of the sputter yield.

The ongoing miniaturization has reached a point where dopants, impurities or active impurities reach the quantum limit, making deterministic single ion implantation (SII) indispensable. Moreover, applications in quantum computing, spintronics, and magnonics require at the same time, a very precise spatial placement of these implants. Other requirements for such an implantation system would be a wide range of available ion species, the ability to implant at extremely low fluence as well as low voltage operation. Our new system, named Tibussii, is expected to address all of these requirements. It will be the first UHV system to include a liquid metal alloy ion source (LMAIS) focused ion beam (FIB) column, a plasma FIB, and a scanning electron microscope (SEM). The 4-nm SEM will be used for damage-free navigation, orientation and inspection. Both FIB columns are mass-separated columns with three Einzellenses, a chicane for neutral particles, and additional blankers and features optimized for single ion implantation. We will show the current status of the system, which is currently being installed and further developed by HZDR and Orsay Physics. To verify the implantation of single ions, we are currently developing a secondary electron (SE) detection system with a sensitivity close to unity. It will be based on a semiconductor detector and is expected to surpass the detection efficiency of existing systems based on electron multiplication, such as channeltrons or microchannel plates.

Broad ion beams have shown their wide applications for materials modification. Focused ion beams can be used in a similar way while simultaneously providing process monitoring. Here, we demonstrate this on a new kind of ion-induced structural evolution. Sub-micrometer Sn spheres were irradiated in a helium ion microscope with a sub-nm beam of 30 keV He ions. Above a fluence of ~10^17/cm², Sn extrusions appeared on the surface of the spheres, which were imaged using the secondary electron signal. Initially, small, pyramid-like faceted extrusions form at the equator of the spheres (north pole pointing to the ion source). Later, each sphere becomes completely covered by the extrusions. A model was developed that assumes that each He ion generate ~70 Frenkel pairs. The implanted helium atoms, interstitials, and vacancies will be confined by the oxide skin of the spheres. Some He atoms will occupy vacancies, which partially prevent their recombination with interstitials. Furthermore, the ion irradiation leads to erosion and opening of the SnO skin. The interstitials can now escape from the interior of the Sn sphere and form an epitaxial regular Sn lattice on the exterior. Transmission electron microscopy, Auger electron spectroscopy as well as TRI3DYN [1] and 3D kinetic lattice Monte Carlo [2] simulations support these findings. In addition, we provide a perspective on focused ion beams from our in-house development and production of liquid metal alloy ion sources, which can be used for applications from self-organized patterning, over altering magnetic or electrical properties, to quantum photonics and computation [3]. [1] Möller, Nucl. Instr. Meth. B 322 (2014) 23 [2] Strobel et al., Phys. Rev. B 64 (2001) 245422 [3] www.hzdr.de/fib

Bei dem Datensatz handelt es sich um die Daten für die Abscheidung von FeSb₂ Nanodrähten auf GaAs-Substraten mit ioneninduzierter Vorstruckturierung. Der Datensatz beinhaltet die AFM-Aufnahme der verwendeten Substratoberfläche und die TEM-Aufnahmen mit den EDXS- udn FFT-Ergebnisse.

Most industrial processes are generating waste heat that can be converted into electrical energy with thermoelectric generators (TEGs). For efficient energy harvesting, it is necessary to significantly improve the properties like Seebeck coefficient, electrical and thermal conductivity of the thermoelectric materials in the TEGs. One promising approach are thermoelectric nanostructures to reduce the thermal conductivity while maintaining constant electrical conductivity and Seebeck coefficient. For that reason, this study investigated the possibility of preparing nanowires of the thermoelectric material iron antimonide (FeSb₂) on crystalline gallium arsenide GaAs(001) substrates with ion-induced surface nanopatterning. The GaAs(001) substrates were pre-patterned using 1 keV Ar⁺ ion irradiation. By using an ion source with a broad, unfocused ion beam at normal incidence, the patterned area can be scaled to nearly any size. The self-organized surface structure is formed by reverse epitaxy and is characterized by almost perfectly parallel-aligned ripples at the nanometer scale. For the fabrication of FeSb₂ nanowires, iron and antimony were successively deposited on the prepatterned GaAs substrates at grazing incidence and then annealed. They were characterized using transmission electron microscopy (TEM), in particular high-resolution TEM imaging for structure analysis and spectrum imaging analysis based on energy-dispersive X-ray spectroscopy for element characterization. With the presented fabrication method, FeSb₂ nanowires were produced successfully on GaAs(001) substrates with an ion-induced nanopatterned surface. The nanowires have a polycristalline structure and a cross-sectional area which is scalable up to 22×22nm². Due to the highly ordered nanostructure of the GaAs substrates, the nanowires have a length of several micrometer. These bottom-up nanofabrication based on ion-induced patterning can be a viable alternative to top-down procedures regarding to effic

Rohdaten Rasterkraftmikroskopie

This work presents first insights into the dynamics of free-surface release clouds from dynamically compressed polystyrene and pyrolytic graphite at pressures up to 200 GPa, where they transform into diamond or lonsdaleite, respectively. These ejecta clouds are released into either vacuum or various types of catcher systems, and are monitored with high-speed recordings (frame rates up to 10 MHz). Molecular dynamics simulations are used to give insights to the rate of diamond preservation throughout the free expansion and the catcher impact process, highlighting the challenges of diamond retrieval. Raman spectroscopy data show graphitic signatures on a catcher plate confirming that the shock-compressed PS is transformed. First electron microscopy analyses of solid catcher plates yield an outstanding number of different spherical-like objects in the size range between ten(s) up to hundreds of nanometres, which are one type of two potential diamond candidates identified. The origin of some objects can unambiguously be assigned, while the history of others remains speculative.

Ion-induced surface patterning has turned out to be a highly versatile technique for many applications where large areas of nanostructured surfaces or thin films are required. Both fundamental and applied research may benefit from in-situ studies revealing the kinetics of the patterning process, yielding further insight into the dominant mechanisms and thus enabling to gain precise process control. The surface-sensitive X-ray scattering technique of Grazing Incidence Small Angle X-Ray Scattering (GISAXS) is a well-suited method for such in-situ investigations, allowing for contact-less examination under various external conditions. Here, we present a real-time in-situ GISAXS investigation of reverse epitaxy patterning in crystalline Ge(001). From the X-ray scattering pattern we deduce the significant morphological parameters of the surface, thus tracking the development of the surface morphology with time during ion irradiation. These findings are compared with results from simulations based on a continuum equation of the local surface height. Good agreement of the simulation with both experiment and theory was only achieved when including in the continuum equation an additional term for regulating the pattern anisotropy. We then find that a continuum equation considering only diffusive effects reproduces the experimentally observed surface patterning kinetics well. Observing the kinetics of pattern formation in the non-linear regime, we find that the temporal evolutions of characteristic length and roughness conform to power laws, their exponents agreeing with scaling laws for conserved continuum equations with four-fold symmetry. Moreover, we find that the facet angle kinetics can be described by the Austin-Rickett equation for diffusion-controlled transformation processes, corroborating our assumption of a predominantly diffusive mechanism of pattern formation.

Broad ion beams have shown their wide applications for materials modification. Focused ion beams can be used in a similar way while simultaneously providing process monitoring. Here, we demonstrate this on a new kind of ion-induced structural evolution. Sub-micrometer Sn spheres were irradiated in a helium ion microscope with a sub-nm beam of 30 keV He ions. Above a fluence of ~10^17/cm², Sn extrusions appeared on the surface of the spheres, which were imaged using the secondary electron signal. Initially, small, pyramid-like faceted extrusions form at the equator of the spheres (north pole pointing to the ion source). Later, each sphere becomes completely covered by the extrusions. A model was developed that assumes that each He ion generate ~70 Frenkel pairs. The implanted helium atoms, interstitials, and vacancies will be confined by the oxide skin of the spheres. Some He atoms will occupy vacancies, which partially prevent their recombination with interstitials. Furthermore, the ion irradiation leads to erosion and opening of the SnO skin. The interstitials can now escape from the interior of the Sn sphere and form an epitaxial regular Sn lattice on the exterior. Transmission electron microscopy, Auger electron spectroscopy as well as TRI3DYN [1] and 3D kinetic lattice Monte Carlo [2] simulations support these findings. In addition, we provide a perspective on focused ion beams from our in-house development and production of liquid metal alloy ion sources, which can be used for applications from self-organized patterning, over altering magnetic or electrical properties, to quantum photonics and computation [3]. [1] Möller, Nucl. Instr. Meth. B 322 (2014) 23 [2] Strobel et al., Phys. Rev. B 64 (2001) 245422 [3] www.hzdr.de/fib

Grazing Incidence Small Angle X-ray Scattering (GISAXS) has been established as a versatile tool for comprehensive morphological characterization of surfaces on the nanometer scale. As a contact-less technique it lends itself especially to in-situ monitoring of surface nanopattern development or the growth of supported nanostructures under various conditions such as reactive atmospheres, high temperatures, applied fields, or ion irradiation. A GISAXS intensity pattern is a representation of the shapes, sizes, as well as lateral and vertical arrangements of three-dimensional structures in reciprocal space, in dependence of the direction of the incident X-ray beam. Complementary to local imaging techniques such as atomic force microscopy (AFM), it provides information on the average surface morphology of the extended area covered by the footprint of the X-ray beam. We implemented an in-situ ultra-high vacuum setup at the ISR beamline of the NSLS-II synchrotron combining GISAXS with low-energy broad-beam ion irradiation, providing sample rotation as well as heating to several hundred degrees Celsius. This setup allows us to observe the nanoscale pattern formation kinetics on crystalline semiconductors in-situ under ion irradiation. We studied the pattern formation on Ge(001) surfaces, where the crystallinity of the surface under ion irradiation is ensured by heating the sample above its recrystallization temperature. The Ge(001) surface is known to develop a pit-and-mound pattern of faceted pyramidal structures under irradiation with 1 keV Ar+ ions. The edges of the pyramidal structures are aligned along the <100> and <010> direction, while their sidewall facets have a uniform polar tilt from the <001> direction. Such a regular surface morphology results in a distinct GISAXS intensity pattern. From the development of the GISAXS pattern features with ion fluence, we can conclude on the corresponding development of the surface morphology. Using this technique, we monitor

Recent developments of heterojunction-based devices through bottom-up approach such as sensors, light-emitters, energy generation and storage have emerged with great interest due to their wide range of operation and application related flexibilities. This work demonstrates how as-grown hydrogen titanate nanotubes (HTNT) bend and wrap on pristine curpous oxide nanowires (CONW) when mixed together. The unique architecture of wrapping followed by junction formation enhances the active surface area and reduces the contact resistance between the adjacent CONW and HTNT. Such a film upon further ion beam irradiation produces a large-scale network of hetero- and homo-junctions. This newly formed thin film surface upon irradiation shows strong water repelling properties and higher electrical conductivity. The wrapping mechanism, bond formation and the change of conductivity are explained using first principles calculations. The ion beam modifications and large-scale joining are predicted by state-of-the-art TRI3DYN simulation, which is based on binary collision approximation and simulated in a Monte Carlo approach. The observed wrapping and heterojunction are expected to provide excellent mechanical strength and flexibility, which are suitable for fabrication of flexible electronic devices.

Enhanced interstitial diffusion in tin is a phenomenon often observed during ion-beam irradiation and in lead-free solders. For the latter, this not very well understood, strain-driven mechanism results in the growth of whiskers, which can lead to unwanted shorts in electronic designs. In ion-beam physics, this phenomenon is often observed as a result of the enhanced formation of Frenkel pairs in the energetic collision cascade. Here, we show how epitaxial growth of tin extrusions on tin-oxide-covered tin spheres can be induced and simultaneously observed by implanting helium using a helium ion microscope. Calculations of collision cascades based on the binary collision approximation and 3D-lattice-kinetic Monte Carlo simulations show that the implanted helium will occupy vacancy sites, leading to a tin interstitial excess. Sputtering and phase separation of the tin oxide skin, which is impermeable for tin atoms, create holes and will allow the epitaxial overgrowth to start. Simultaneously, helium accumulates inside the irradiated spheres. Fitting the simulations to the experimentally observed morphology allows us to estimate the tin to tin-oxide interface energy to be 1.98 J m−2 . Our approach allows the targeted initiation and in situ observation of interstitial diffusion-driven effects to improve the understanding of the tin-whisker growth mechanism observed in lead-free solders.

In this chapter, we extend the discussion of curvature effects in magnetism towards the description of geometrically curved magnetic thin shells. A self-consistent micromagnetic framework of curvilinear magnetism describes the impact of curvature–induced effects, driven by both local and nonlocal interactions, on the statics and dynamics of magnetic textures in extended curved thin shells. In particular, we focus on the effects in magnetic thin films with in-plane and out-of-plane easy axis of magnetization on spherical, cone-, bump-, and indentation-like objects. The special interest will be addressed to skyrmions in curved magnetic films. Statics of skyrmions as well as their magnetization dynamics will be considered. We provide an overview of relevant experimental methods, which allow fabricating these geometrically curved extended thin films including nanosphere lithography, ion beam induced surface patterning and also chemical synthesis approaches to realize metal and oxide hollow nanostructures with a tunable morphology. We anticipate that the strong theoretical background on the fundamental understanding of the curvature effects in geometrically curved magnetic shells and the availability of the fabrication methods to produce these architectures will stimulate experimental activities targeting the validation of the exciting theoretical predictions including curvature–induced skyrmions, pinning of chiral domain walls on local bends and exploring novel nonlocal chiral symmetry breaking effects.

Raw data for the publication: "Epitaxial lateral overgrowth of tin spheres driven and directly observed by helium ion microscopy". It contains helium ion microscopy, transmission electron microscopy, scanning electron microscopy as well as gallium focused ion microscopy images and XPS data. It shows how the irradiation of tin spheres with keV He ions causes epitaxial lateral overgrowth.

experimental raw data: in-situ Grazing Incidence Small Angle X-ray Scattering (GISAXS), ex-situ Atomic Force Microscopy (AFM); simulated raw data: surface topography (RIDO)

Broad ion irradiation of nanoobjects can considerably change their shape. Examples are ion-beam hammering [1], ion-induced shaping of buried particles [2], and ion-induced viscous flow of nanopillars [3]. Such shape changes are mainly driven by the kinetics of defects generated by binary collisions of ions and recoils. Here we report a new kind of ion-induced structure evolution. Sub-micrometer Sn spheres were irradiated with 30 keV He+ ions in a Helium Ion Microscope (HIM). Above a He+ fluence of ~ 10E17 /cm², Sn extrusions appear on the surface of the spheres and were imaged with the HIM. Initially, small, pyramid-like facetted extrusions form at the equator of the tin spheres (north pole pointing to the ion source). Later, each sphere becomes completely covered with tin and appears like a facetted single crystal cube. No Sn extrusions were observed for tin spheres with diameters smaller than ~100 nm. Transmission Electron Microscopy and Auger electron spectroscopy studies show that the tin spheres are covered with a few nm thick SnOx skin and that the extrusions are single crystals. A model was developed which assumes that the He+ ions generate Frenkel pairs in the body-centered tetragonal lattice of tin. The point defects are confined to the tin sphere by the SnO skin, and there is no preferred nucleation or annihilation of the point defects at the Sn-SnO interface. The recombination of interstitials with vacancies is partly inhibited by occupation with He atoms. This results in an increasing pressure of the “interstitial gas”. Simultaneously, He+ ion erosion creates openings in the SnO skin. The sputter coefficient increases with the angle of incidence, so that openings in the SnO skin form in the equator regions first. Once the tin interstitials find an opening in the SnO skin, they can escape from the interior of the Sn sphere and form an epitaxial regular Sn lattice on the outside. Due to the high Sn-SnO bond strength, the extruded tin wets the outer SnO sur

The ion-induced nanoscale pattern formation on a crystalline Ge(001) surface is observed in-situ by means of Grazing Incidence Small Angle X-ray Scattering (GISAXS). Analysis of the GISAXS intensity maps yields the temporal develoment of geometric parameters characterizing the changing pattern morphology. In comparison with theoretical predictions and with simulations of the patterning process based on a continuum equation we find good agreement for the temporal evolution of the polar facet angle, characteristic length, and surface roughness in the non-linear regime. To achieve this agreement, we included an additional term in the continuum equation which adjusts the pattern anisotropy.

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 semi-metallic properties 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's 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.