Electron-assisted oxidation of Co–Si-based focused electron beam induced deposition (FEBID) materials is shown to form an oxide bilayer with a total thickness of less than 15 nm by phase separation.

The investigation of precursor classes for the fabrication of nanostructures is of specific interest for maskless fabrication and direct nanoprinting. In this study, the differences in material composition depending on the employed process are illustrated for focused-ion-beam- and focused-electron-beam-induced deposition (FIBID/FEBID) and compared to the thermal decomposition in chemical vapor deposition (CVD). This article reports on specific differences in the deposit composition and microstructure when the (H3Si)2Fe(CO)4 precursor is converted into an inorganic material. Maximum metal/metalloid contents of up to 90 at. % are obtained in FIBID deposits and higher than 90 at. % in CVD films, while FEBID with the same precursor provides material containing less than 45 at. % total metal/metalloid content. Moreover, the Fe:Si ratio is retained well in FEBID and CVD processes, but FIBID using Ga+ ions liberates more than 50% of the initial Si provided by the precursor. This suggests that precursors for FIBID processes targeting binary materials should include multiple bonding such as bridging positions for nonmetals. In addition, an in situ method for investigations of supporting thermal effects of precursor fragmentation during the direct-writing processes is presented, and the applicability of the precursor for nanoscale 3D FEBID writing is demonstrated.

Hyperthermia, as the process of heating a malignant site above 42 °C to trigger cell death, has emerged as an effective and selective cancer therapy strategy. Various modalities of hyperthermia have been proposed, among which magnetic and photothermal hyperthermia are known to benefit from the use of nanomaterials. In this context, we introduce herein a hybrid colloidal nanostructure comprising plasmonic gold nanorods (AuNRs) covered by a silica shell, onto which iron oxide nanoparticles (IONPs) are subsequently grown. The resulting hybrid nanostructures are responsive to both external magnetic fields and near-infrared irradiation. As a result, they can be applied for the targeted magnetic separation of selected cell populations - upon targeting by antibody functionalization - as well as for photothermal heating. Through this combined functionality, the therapeutic effect of photothermal heating can be enhanced. We demonstrate both the fabrication of the hybrid system and its application for targeted photothermal hyperthermia of human glioblastoma cells.

Focused ion beam induced deposition (FIBID) is a direct‐write technique enabling the growth of individual nanostructures of any shape and dimension with high lateral resolution. Moreover, the fast and reliable writing of periodically arranged nanostructures can be used to fabricate devices for the investigation of collective phenomena and to design novel functional metamaterials. Here, FIBID is employed to prepare dc‐Josephson junction arrays (dc‐JJA) consisting of superconducting NbC dots coupled through the proximity effect via a granular metal layer. The fabrication is straightforward and allows the preparation of dc‐JJA within a few seconds. Microstructure and composition of the arrays are investigated by transmission electron microscopy and energy dispersive X‐ray spectroscopy. The superconductor‐to‐metal transition of the prepared dc‐JJA is studied in a direct way, by tuning the Josephson junction resistance in 70 nm‐spaced superconducting NbC dots. The observed magnetoresistance oscillations with a period determined by the flux quantum give evidence for the coherent charge transport by paired electrons. Moreover, the measured resistance minima correspond to two fundamental matching configurations of fluxons in the dc‐JJA, caused by magnetic frustration. The robust properties of the prepared dc‐JJA demonstrate the opportunities for a fast preparation of complex device configurations using direct‐write approaches.

AbstractNanomaterialien lassen sich direkt auf eine Oberfläche schreiben, indem Elektronen die Zersetzung von Vorstufen induzieren. Damit ist die Morphologie der Nanostrukturen kontrollierbar, und der Untergrund bleibt unbeschädigt. So entstehen etwa Spitzen für die Rasterkraftmikroskopie.

Direct-write techniques for the fabrication of nanostructures are of specific interest due to their ability for a maskless fabrication of any arbitrary three-dimensional shape. To date, there is a very limited number of reports describing differences in the focused ion and electron beam induced deposition (FIBID/FEBID) for the same precursor species. This report contributes to filling this gap by testing two single-source precursors for the deposition of cobalt silicide in Ga-ion beam writing and reveals H2Si(Co(CO)4)2 to be a very suitable precursor for the technique retaining the 2:1 ratio of Co:Si in the deposit. Maximum metal/metalloid contents of up to 90 atom % are obtained in FIBID deposits, while FEBID with the same precursor provides material containing <60 atom % total metal/metalloid content. A dense deposit is obtained by using FEBID showing paramagnetic behavior and electric properties of a granular metal. In contrast, the FIBID material is porous and the expected ferromagnetic and temperature-dependent electric properties for dicobalt silicide have been observed. Further analysis enabled the proposition of different dominating material conversion channels based on the observed microstructural features including bubble formation in FIBID-derived material. The differences in materials properties depending on the deposition strategy can influence the cobalt silicide deposits' applicability in nanoelectronics and spintronics.

A series of new mixed-substituted heteronuclear precursors with preformed Si-Ge bonds has been synthesized via a two-step synthesis protocol. The molecular sources combine convenient handling with sufficient thermal lability to provide access to group IV alloys with low carbon content. Differences in the molecule-material conversion by chemical vapor deposition (CVD) techniques are described and traced back to the molecular design. This study illustrates the possibility of tailoring the physical and chemical properties of single-source precursors for their application in the CVD of Si1-xGex coatings. Moreover, partial crystallization of the Si1-xGex has been achieved by Ga metal-supported CVD growth, which demonstrated the potential of the presented precursor class for the synthesis of crystalline group IV alloys.

The material composition and electrical properties of nanostructures obtained from focused electron beam-induced deposition (FEBID) using manganese and vanadium carbonyl precursors have been investigated. The composition of the FEBID deposits has been compared with thin films derived by the thermal decomposition of the same precursors in chemical vapor deposition (CVD). FEBID of V(CO)6 gives access to a material with a V/C ratio of 0.63–0.86, while in CVD a lower carbon content with V/C ratios of 1.1–1.3 is obtained. Microstructural characterization reveals for V-based materials derived from both deposition techniques crystallites of a cubic phase that can be associated with VC1−xOx. In addition, the electrical transport measurements of direct-write VC1−xOx show moderate resistivity values of 0.8–1.2 × 103 µΩ·cm, a negligible influence of contact resistances and signatures of a granular metal in the temperature-dependent conductivity. Mn-based deposits obtained from Mn2(CO)10 contain ~40 at% Mn for FEBID and a slightly higher metal percentage for CVD. Exclusively insulating material has been observed in FEBID deposits as deduced from electrical conductivity measurements. In addition, strong tendencies for postgrowth oxidation have to be considered.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

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.

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 results 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 outmost 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 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 technique.

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.

Mixed-metal carbonyls are a family of compounds which can be used to fabricate bimetallic nanostructures by means of focused electron beam induced deposition. In the present work, we show that silicon-metal alloys can be prepared by using silyl-metal carbonyls. In particular, we employ the SiH3Mn(CO)5 precursor to fabricate Mn–Si alloy nanowires, with composition of about 34 at% Mn, 17 at% Si, 31 at% C and 18 at% O, as revealed by energy dispersive x-ray analysis. Magnetotransport measurements are carried out on as-grown samples and on samples treated after-growth by low-energy electron irradiation. All the samples exhibit a quasi-metallic temperature-dependent behavior. Hall-effect measurements indicate either electron-like transport, for as-grown samples, or hole-like transport, for post-growth treated samples, respectively. Correspondingly, the charge carrier density increases from cm−3 to cm−3. We find a small negative transversal magnetoresistance, which depends on irradiation dose and temperature. Microstructural investigations carried out by transmission electron microscopy indicate that the samples are constituted by an amorphous Mn2Si phase embedded in a carbonaceous matrix. Additionally, in treated samples a novel Mn2SiO4 spinel oxide phase is observed.

Thioether-functionalised indium aminoalcoholates have been used as single-source precursors in aerosol-assisted CVD processes. The obtained In2O3-x S-x 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 [< 62% (S/(S + O)) for the n-butyl derivatives]. In addition to thin films, polycrystalline 1D structures are obtained at slightly modified synthesis conditions. The materials are analysed by EDX, XRD, XPS, SEM, and TEM.