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Magnonics is a rapidly developing domain of nanomagnetism, with application potential in information processing systems. Realisation of this potential and miniaturisation of magnonic circuits requires their extension into the third dimension. However, so far, magnonic conduits are largely limited to thin films and 2D structures. Here, we introduce 3D magnonic nanoconduits fabricated by the direct write technique of focused-electron-beam induced deposition (FEBID). We use Brillouin light scattering (BLS) spectroscopy to demonstrate significant qualitative differences in spatially resolved spin-wave resonances of 2D and 3D nanostructures, which originates from the geometrically induced non-uniformity of the internal magnetic field. This work demonstrates the capability of FEBID as an additive manufacturing technique to produce magnetic 3D nanoarchitectures and presents the first report of BLS spectroscopy characterisation of FEBID conduits.

Two new precursors for focused electron beam-induced deposition (FEBID) of cobalt silicides have been synthesized and evaluated. The H3SiCo(CO)4 and H2Si(Co(CO)4)2 single-source precursors retain the initial metal ratios and show low sensitivity to changes in the FEBID parameters such as acceleration voltage, beam current, and precursor pressure. The precursors allow the direct writing of material containing ∼55 to 60 at % total metal/metalloid content combined with high growth rates. During the deposition process an average of ∼80% of the carbonyl ligands are cleaved off in these planar deposits. Postgrowth electron curing does not change the deposits' composition, but resistivities decrease after the curing procedure. Temperature-dependent electrical properties indicate the presence of a granular metal for both cured samples and the as-grown Co2Si deposit, while the as-grown CoSi material is on the insulating side of the metal-insulator transition. The observed magnetoresistance behavior is indicative of tunneling magnetoresistance and is substantially reduced upon postgrowth irradiation treatment.

In the past decades, group IV nanowires and nanoparticles have been the subject of extensive research. Beside tremendous progress in morphological control and integration in advanced device archite...

Focused electron beam-induced deposition (FEBID) is a maskless, direct-write nanolithography approach for the growth of nanostructures. In recent years, significant progress has been made demonstrating highly controlled writing processes with complex nanostructure geometries and intricate methods of preparing inorganic deposits of sufficient purity for applications in materials science and condensed matter physics. For instance, fields of research include sensors, electrical contacts, magnetics, photonics etc. The deposition process itself is simple and highly complex at the same time. Interdisciplinary efforts are required to understand individual reaction paths in the molecule–electron interactions and the impact of several parameters governing the overall process that determines the material's composition. Since the deposition hinges on volatile precursors, a description of chemical aspects and potential avenues for the development of tailored precursor synthesis are described herein. Literature data are used to describe the process and the influence of the precursor constitution on the deposits’ nature. Results on molecule–electron interactions in the gas phase as well as condensed precursor layers are compared to FEBID deposit's composition illustrating the benefits and shortcomings of these supporting investigations in explaining the precursor decomposition characteristics in FEBID processes. This is also associated with the need of understanding the role of deposition conditions and reporting as many details as possible in experimental sections, which is of utmost importance in order to ensure reproducibility of reported data in the FEBID community. Moreover, we outline the potential impact of the vacuum level and associated water content in the deposition equipment on the deposited material's composition, which should be a major contributor to the compositional variations being described in the literature. A few additional experiments are suggested to unravel the impact of this parameter enabling secondary reaction paths in the FEBID process initiated by water–molecule–electron interactions. Finally, we summarize the classes of precursors used for FEBID to date and add our thoughts on approaches how to choose new precursors for this direct-write technique.

Highly oriented Ge 0.81Sn 0.19 nanowires have been synthesized by a low-temperature chemical vapor deposition growth technique. The nanostructures form by a self-seeded vapor-liquid-solid mechanism. In this process, liquid metallic Sn seeds enable the anisotropic crystal growth and act as a sole source of Sn for the formation of the metastable Ge 1-xSn x semiconductor material. The strain relaxation for a lattice mismatch of ϵ = 2.94% between the Ge (111) substrate and the constant Ge 0.81Sn 0.19 composition of nanowires is confined to a transition zone of 1-xSn x structures with diameters in the micrometer range show a 5-fold longer compositional gradient very similar to epitaxial thin-film growth. Effects of the Sn growth promoters' dimensions on the morphological and compositional evolution of Ge 1-xSn x are described. The temperature- and laser power-dependent photoluminescence analyses verify the formation of a direct band gap material with emission in the mid-infrared region and values expected for unstrained Ge 0.81Sn 0.19 (e.g., band gap of 0.3 eV at room temperature). These materials hold promise in applications such as thermal imaging and photodetection as well as building blocks for group IV-based mid- to near-IR photonics.

Superconducting planar nanostructures are widely used in applications, e.g., for highly sensitive magnetometers and in basic research, e.g., to study finite size effects or vortex dynamics. In contrast, 3D superconducting nanostructures, despite their potential in quantum information processing and nanoelectronics, have been addressed only in a few pioneering experiments. This is due to the complexity of fabricating 3D nanostructures by conventional techniques such as electron-beam lithography and to the scarce number of superconducting materials available for direct-writing techniques, which enable the growth of 3D free-standing nanostructures. Here, we present a comparative study of planar nanowires and free-standing 3D nanowires fabricated by focused electron- and ion (Ga+)-beam induced deposition (FEBID and FIBID) using the precursor Nb(NMe

A methodology based on the use of Electron Beam Lithography for contacting individual nanowires on top of non-flat micromembranes and microhotplates has been implemented, and the practical details have been exhaustively described. The different fabrication steps have been adapted to the substrate’s topology, requiring specific holders and conditions. The methodology is demonstrated on individual SnO2 nanowires, which, after fabrication, have been characterized as functional resistive gas nanosensors towards NH3 and benchmarked against similar devices fabricated using more conventional Dual Beam Focused Ion Beam techniques, demonstrating the superior properties of the here presented methodology, which can be further extended to other non-conventional suspended substrates and nanomaterials.

Varying the growth conditions of gallium-seeded germanium nanostructures leads to significant variations in morphology, and particularly of the electronic properties inducing a transition from the ...

Extending nanostructures into the third dimension has become a major research avenue in modern magnetism, superconductivity and spintronics, because of geometry-, curvature- and topology-induced phenomena. Here, we introduce Co-Fe nanovolcanoes-nanodisks overlaid by nanorings-as purpose-engineered 3D architectures for nanomagnonics, fabricated by focused electron beam induced deposition. We use both perpendicular spin-wave resonance measurements and micromagnetic simulations to demonstrate that the rings encircling the volcano craters harbor the highest-frequency eigenmodes, while the lower-frequency eigenmodes are concentrated within the volcano crater, due to the non-uniformity of the internal magnetic field. By varying the crater diameter, we demonstrate the deliberate tuning of higher-frequency eigenmodes without affecting the lowest-frequency mode. Thereby, the extension of 2D nanodisks into the third dimension allows one to engineer their lowest eigenfrequency by using 3D nanovolcanoes with 30% smaller footprints. The presented nanovolcanoes can be viewed as multi-mode microwave resonators and 3D building blocks for nanomagnonics., Comment: 5 pages, 4 figures

Despite being known of for decades, the actual realization of memory devices based on the memristive effect is progressing slowly, due to processing requirements and the need for exotic materials which are not compatible with today’s complementary-metal-oxide-semiconductor (CMOS) technology. Here, we report an experimental study on a Ge quantum wire device featuring distinct signatures of memristive behavior favorable for integration in CMOS platform technology. Embedding the quasi-1D Ge quantum wire into an electrostatically modulated back-gated field-effect transistor, we demonstrate that individual current transport channels can be addressed directly by controlling the surface trap assisted electrostatic gating. The resulting quantization of the current represents the ultimate limit of memristors with practically zero off-state current and low footprint. In addition, the proposed device has the advantage of non-destructive successive reading cycles capability. Importantly, our findings provide a framework towards fully CMOS compatible ultra-scaled Ge based memristors.

Focused-electron-beam-induced deposition (FEBID) constitutes a direct-writing maskless technique, which has been employed to prepare nanodots, nanolines, as well as laminar and even three-dimensional nanostructures with potential in many technological fields. Here, we report direct-writing of functional nanostructures with the HFeCo3(CO)12 bimetallic carbonyl precursor. The metal content as well as the magnetotransport properties of Fe–Co–C–O deposits were reproducibly tuned upon ex situ postgrowth annealing at 100, 200, and 300 °C in a high-vacuum system. The atomic composition obtained by energy-dispersive X-ray spectroscopy (EDX) analysis revealed that carbonyl groups release during annealing, although principally sole oxygen is released from the deposits, yielding an atomic ratio of Co:Fe:C:O = 52:17:22:9 with respect to the atomic composition of as-grown Co:Fe:C:O = 41:13:26:20. Interestingly, the amorphous carbon contained in the as-grown material turns into graphite nanocrystals with an average siz...

The Ga-assisted formation of Ge nanorods and nanowires in solution has been demonstrated and a catalytic activity of the Ga seeds was observed. The synthesis of anisotropic single-crystalline Ge nanostructures was achieved at temperatures as low as 170 °C. Gallium not only serves as nucleation seed but is also incorporated in the Ge nanowires in higher concentrations than its thermodynamic solubility limit. Graphical abstract Electronic supplementary material The online version of this article (10.1007/s00706-018-2191-1) contains supplementary material, which is available to authorized users.

A new method for the site-selective synthesis of nanowires has been developed to enable material growth with defined morphology and, at the same time, different composition on the same chip surface. The chemical vapor deposition approach for the growth of these nanowire-based resistive devices using micromembranes can be easily modified and represents a simple, adjustable fabrication process for the direct integration of nanowire meshes in multifunctional devices. This proof-of-concept study includes the deposition of SnO2, WO3, and Ge nanowires on the same chip. The individual resistors exhibit adequate gas sensing responses toward changing gas concentrations of CO, NO2, and humidity diluted in synthetic air. The data have been processed by principal component analysis with cluster responses that can be easily separated, and thus, the devices described herein are in principle suitable for environmental monitoring.

The use of bimetallic precursors in focused electron beam induced deposition (FEBID) allows mixed metal nanostructures with well-defined metal ratios to be generated in a single step process. HFeCo3(CO)12 is an example of one such bimetallic precursor that has previously been shown to form deposits with unusually high metal content (>80%) as compared to that of typical FEBID deposits (

Metastable germanium–tin alloys are promising materials for optoelectronics and optics. Here we present the first electrical characterization of highly crystalline Ge0.81Sn0.19 nanowires grown in a solution-based process. The investigated Ge0.81Sn0.19 nanowires reveal ohmic behavior with resistivity of the nanowire material in the range of ∼1 × 10−4 Ω m. The temperature-dependent resistivity measurements demonstrate the semiconducting behavior. Moreover, failure of devices upon heating to moderate temperatures initiating material degradation has been investigated to illustrate that characterization and device operation of these highly metastable materials have to be carefully conducted.

Over its rather long history, focused electron beam induced deposition (FEBID) has mostly been used as an auxiliary process in passivating surfaces in sample preparation for transmission electron microscopy. This has changed over the last one and a half decades. On the one hand, FEBID has been established as the leading technical approach to lithography mask repair on the industrial scale. On the other hand, FEBID-related technical and methodological developments, FEBID-derived materials, and FEBID-based device fabrication have had a significant impact in various areas of basic and applied research, such as nanomagnetism and superconductivity, plasmonics, and sensing. Despite this dynamic development, the FEBID user base does still form a rather exclusive club of enthusiasts. In this Perspective, our aim is to provide sufficient insight into the basics of FEBID, its potential, as well as its challenges, to scientists working in the broader fields of materials science, nanotechnology, and device development. It is our hope to spark growing interest and even excitement into FEBID which, as we believe, still has to live up to its full potential.

Ge1–xSnx nanorods (NRs) with a nominal Sn content of 28% have been prepared by a modified microwave-based approach at very low temperature (140 °C) with Sn as growth promoter. The observation of a Sn-enriched region at the nucleation site of NRs and the presence of the low-temperature α-Sn phase even at elevated temperatures support a template-assisted formation mechanism. The behavior of two distinct Ge1–xSnx compositions with a high Sn content of 17% and 28% upon thermal treatment has been studied and reveals segregation events occurring at elevated temperatures, but also demonstrates the temperature window of thermal stability. In situ transmission electron microscopy investigations revealed a diffusion of metallic Sn clusters through the Ge1–xSnx NRs at temperatures where the material composition changes drastically. These results are important for the explanation of distinct composition changes in Ge1–xSnx and the observation of solid diffusion combined with dissolution and redeposition of Ge1–ySny (...

Thioether-functionalised indium aminoalcoholates have been used as single-source precursors in aerosol-assisted CVD processes. The obtained In2O3−xSx oxysulphide deposits show either a single indium sulphide phase for deposits with high sulphide content [>75% (S/(S + O)) for the t-butyl derivatives] or pronounced phase separation in indium oxide and indium sulphide for lower sulphide content [

The gas sensing properties of germanium (Ge) monocrystalline nanowires (NWs) at temperatures up to 100 °C have been demonstrated for the first time. The devices have been fabricated based on an energy efficient and site-specific vapor-liquid-solid growth of NW meshes on top of microhotplates, which contain a buried heater and top electrodes. The devices have been investigated for the detection of oxygen, nitrogen dioxide and carbon monoxide gases, showing the important effect played by pre-adsorbed surface oxygen in the response to the different gases. The Ge NW-based devices exhibit p-type conductivity and show high selectivity in their response towards water vapor. Water vapor interaction is not dependent on the presence of oxygen and the adsorption leads to electron donation in the Ge nanowires. TEM analysis of the NWs proves that they are covered by a thin, outer germanium oxide layer, which is stable and does not grow upon exposure to these gases and operation temperatures up to 100 °C. The presence of this oxide layer plays a key role in the sensing mechanisms.

Nanowires with inhomogeneous heterostructures such as polytypes and periodic twin boundaries are interesting due to their potential use as components for optical, electrical, and thermophysical applications. Additionally, the incorporation of metal impurities in semiconductor nanowires could substantially alter their electronic and optical properties. In this highlight article, we review our recent progress and understanding in the deliberate induction of imperfections, in terms of both twin boundaries and additional impurities in germanium nanowires for new/enhanced functionalities. The role of catalysts and catalyst–nanowire interfaces for the growth of engineered nanowires via a three-phase paradigm is explored. Three-phase bottom-up growth is a feasible way to incorporate and engineer imperfections such as crystal defects and impurities in semiconductor nanowires via catalyst and/or interfacial manipulation. “Epitaxial defect transfer” process and catalyst–nanowire interfacial engineering are employed to induce twin defects parallel and perpendicular to the nanowire growth axis. By inducing and manipulating twin boundaries in the metal catalysts, twin formation and density are controlled in Ge nanowires. The formation of Ge polytypes is also observed in nanowires for the growth of highly dense lateral twin boundaries. Additionally, metal impurity in the form of Sn is injected and engineered via third-party metal catalysts resulting in above-equilibrium incorporation of Sn adatoms in Ge nanowires. Sn impurities are precipitated into Ge bi-layers during Ge nanowire growth, where the impurity Sn atoms become trapped with the deposition of successive layers, thus giving an extraordinary Sn content (>6 at.%) in Ge nanowires. A larger amount of Sn impingement (>9 at.%) is further encouraged by utilizing the eutectic solubility of Sn in Ge along with impurity trapping.

Indium oxide nanostructures have been prepared by carbothermal reduction method. From them, nanowires have been structurally and optically characterized using X-ray diffraction, scanning and transmission electron microscopy and photoluminescence. The indium oxide nanowires have been removed from the substrate and contacted by Focused Electron- and Focused Ion-Beam Induced Deposition techniques to interdigitates on suspended microhotplates, which allow heating up to 300 °C with a low power consumption of only 8 mW. The gas response of the tested devices towards ethanol, carbon monoxide and nitrogen dioxide diluted in dry synthetic air at different concentrations and temperatures has been carried out showing a selectivity towards ethanol with responses up to 50% at temperatures between 200 and 300 °C, while only small response to high concentrations of carbon monoxide and nitrogen dioxide is observed.

Highly oriented Ge

A new method for the site-selective synthesis of nanowires has been developed to enable the material growth with specific morphology and different compositions on one single chip. Based on a modification of the chemical vapor deposition method, the growth of nanowires on top of micromembranes can be easily tuned and represents a simple and adjustable fabrication process for the direct integration of different nanowire-based resistive multifunctional devices. This proof-of-concept is exemplified by the deposition of SnO2, WO3 and Ge nanowires on the membranes of one single chip and their gas sensing responses towards different concentrations of CO, NO2 and humidity diluted in synthetic air are evaluated. The principal component analysis of the collected data allows gas identification and, thus, the system is suitable for environmental monitoring.

Nanowires of different materials have been grown site-selectively and integrated in one single chip using a new methodology. The chemical vapor deposition approach performed to grow these nanowire-based devices can be easily tuned, representing a simple, fast and adjustable fabrication process for the direct integration of nanowire meshes in multifunctional devices. This proof-of-concept study focuses on the deposition of SnO 2 , WO 3 and Ge nanowires on the same chip. The prepared sensors have been tested under varying concentrations of CO, NO 2 and humidity diluted in synthetic air, exhibiting satisfactory gas sensing responses. A principal component analysis has been performed with the collected data and responses towards different gases can be easily classified in clusters. Therefore, the devices here presented are suitable for environmental monitoring.

A better understanding of the electrodynamic behavior of cells interacting with electric fields would allow for novel scientific insights and would lead to the next generation of cell manipulation, diagnostics, and treatment. Here, we introduce a promising electrode design by using metal oxide high-k dielectric passivation. The thermally generated dielectric passivation layer enables efficient electric field coupling to the fluid sample comprising cells while simultaneously decoupling the electrode ohmically from the electrolyte, allowing for better control and adjustability of electric field effects due to reduced electrochemical reactions at the electrode surface. This approach demonstrates cell-size specific lysis with electric fields in a microfluidic flow-through design resulting in 99.8% blood cell lysis at 6 s exposure without affecting the viability of Gram-positive and Gram-negative bacterial spike-ins. The advantages of this new approach can support next-generation investigations of electrodynamics in biological systems and their exploitation for cell manipulation in multiple fields of medicine, life science, and industry.

The thermolysis behaviour of a new class of metal alkoxides containing a thioether functionality in the alkyl chain is described. Homoleptic gallium alkoxides with sufficient volatility have been investigated in low pressure chemical vapour deposition (CVD) showing the potency of the thioether to act as a sulphidisation agent during decomposition of the precursor leading to Ga2O3−xSx films. Similar thermolysis experiments were conducted in high boiling point solvents leading to Ga2O3−xSx and In2O3−xSx particles. The thermolysis products have been investigated by SEM, EDX, XRD and XPS. Moreover, initial tests of the electrical transport properties of amorphous Ga2O3−xSx films have been conducted, showing increased conductivity and altered activation energies for the sulphur containing films.

Ge NWs have been selectively grown directly on top of the suspended microhotplates, with heater and interdigitated electrodes, via Au catalyzed Vapor Liquid Solid (VLS) mechanism through a low-power consumption CVD-like process. The so-fabricated devices, with a p-type semiconductors behavior, have been characterized towards water vapor in synthetic air, keeping the temperature at 100°C in order to achieve a stable oxide. The results show reproducible responses towards H 2 O.

The synthesis of novel, homoleptic group 13 alkoxides is presented. M(OCH(CH2NR2)2)3, where M=Al, Ga, In and R=Me, Et, are characterised by room temperature NMR spectroscopy and single-crystal XRD showing the monomeric nature of all aminoalcoholates.

Strategien, um ungewohnliche metastabile Phasen herzustellen, basieren oft auf Prinzipien der Festkorperchemie. Nutzt die Synthese Template oder andere Molekule, erweitern sich die Zusammensetzungen der Nanostrukturen.

Three-dimensional (3D) nanomagnetism, where spin configurations extend into the vertical direction of a substrate plane allow for more complex, hierarchical systems and the design of novel magnetic effects. As an important step towards this goal, we have recently demonstrated the direct-write fabrication of freestanding ferromagnetic 3D nano-architectures of ferromagnetic CoFe in shapes of nano-tree and nano-cube structures by means of focused electron beam induced deposition. Here, we present a comprehensive characterization of the magnetic properties of these structures by local stray-field measurements using a high-resolution micro-Hall magnetometer. Measurements in a wide range of temperatures and different angles of the externally applied magnetic field with respect to the surface plane of the sensor are supported by corresponding micromagnetic simulations, which explain the overall switching behavior of in part rather complex magnetization configurations remarkably well. In particular, the simulations yield coercive and switching fields that are in good quantitative correspondence with the measured coercive and switching fields assuming a bulk metal content of 100 at % consisting of bcc Co 3 Fe. We show that thermally-unstable magnetization states can be repetitively prepared and their lifetime controlled at will, a prerequisite to realizing dynamic and thermally-active magnetic configurations if the building blocks are to be used in lattice structures.