Focused Ion Beam Induced Deposition Research Articles

Improvement of MEMS Thermomechanical Actuation Efficiency by Focused Ion Beam-Induced Deposition

Improvement of MEMS Thermomechanical Actuation Efficiency by Focused Ion Beam-Induced Deposition

Rubidium focused ion beam induced platinum deposition

This work presents characterization of focused ion beam induced deposition (FIBID) of platinum using both rubidium and gallium ions. Trimethylplatinum [(MeCp)Pt(Me)3] was used as the deposition precursor. Under similar beam energies, 8.5 keV for Rb+ and 8.0 keV for Ga+, and beam current, near 10 pA, the two ion species deposited Pt films at 0.90 and 0.73 μm3/nC, respectively. Energy-dispersive x-ray spectroscopy shows that Rb+ FIBID-Pt consists of similar Pt contents (49% for Rb+ FIBID and 37% for Ga+ FIBID) with much lower primary ion contents (5% Rb and 27% Ga) than Ga+ FIBID-Pt. The deposited material was also measured to have a resistivity of 8.1×104 μΩcm for the Rb+ FIBID-Pt and 5.7×103 μΩcm for Ga+ FIBID-Pt.

Site-Selective Chemical Vapor Deposition on Direct-Write 3D Nanoarchitectures.

Recent advancements in additive manufacturing have enabled the preparation of free-shaped 3D objects with feature sizes down to and below the micrometer scale. Among the fabrication methods, focused electron beam- and focused ion beam-induced deposition (FEBID and FIBID, respectively) associate a high flexibility and unmatched accuracy in 3D writing with a wide material portfolio, thereby allowing for the growth of metallic to insulating materials. The combination of the free-shaped 3D nanowriting with established chemical vapor deposition (CVD) techniques provides attractive opportunities to synthesize complex 3D core-shell heterostructures. Hence, this hybrid approach enables the fabrication of morphologically tunable layer-based nanostructures with the great potential of unlocking further functionalities. Here, the fundamentals of such a hybrid approach are demonstrated by preparing core-shell heterostructures using 3D FEBID scaffolds for site-selective CVD. In particular, 3D microbridges are printed by FEBID with the (CH3)3CH3C5H4Pt precursor and coated by thermal CVD using the Nb(NMe2)3(N-t-Bu) and HFeCo3(CO)12 precursors. Two model systems on the basis of CVD layers consisting of a superconducting NbC-based layer and a ferromagnetic Co3Fe layer are prepared and characterized with regard to their composition, microstructure, and magneto-transport properties.

Low-resistivity, high-resolution W-C electrical contacts fabricated by direct-write focused electron beam induced deposition.

Background: The use of a focused ion beam to decompose a precursor gas and produce a metallic deposit is a widespread nanolithographic technique named focused ion beam induced deposition (FIBID). However, such an approach is unsuitable if the sample under study is sensitive to the somewhat aggressive exposure to the ion beam, which induces the effects of surface amorphization, local milling, and ion implantation, among others. An alternative strategy is that of focused electron beam induced deposition (FEBID), which makes use of a focused electron beam instead, and in general yields deposits with much lower metallic content than their FIBID counterparts. Methods: In this work, we optimize the deposition of tungsten-carbon (W-C) nanowires by FEBID to be used as electrical contacts by assessing the impact of the deposition parameters during growth, evaluating their chemical composition, and investigating their electrical response. Results: Under the optimized irradiation conditions, the samples exhibit a metallic content high enough for them to be utilized for this purpose, showing a room-temperature resistivity of 550 μΩ cm and maintaining their conducting properties down to 2 K. The lateral resolution of such FEBID W-C metallic nanowires is 45 nm. Conclusions: The presented optimized procedure may prove a valuable tool for the fabrication of contacts on samples where the FIBID approach is not advised.

Superconducting W-C nanopillars fabricated by Ga+ focused ion beam induced deposition

Ga+ Focused Ion Beam Induced Deposition (FIBID) is a highly flexible, single-step nanopatterning technique that makes use of a focused beam of Ga+ ions to locally induce the decomposition of a gaseous precursor material. In combination with the W(CO)6 precursor, Ga+ FIBID is known to yield a W–C compound that is superconducting below 4.7 ​K. While most reports on Ga+ FIBID-grown W–C focus on in-plane patterning, we demonstrate here that growth along the vertical direction may also be achieved by successively stacking a series of individual patterns that get deposited on top of each other. The nanopillars obtained following this procedure reach up to 10 ​μm in height, and have an aspect ratio of around 50. They exhibit a 68% of metallic W in terms of atomic content, higher than the 40% detected in their in-plane counterparts, while maintaining the superconducting properties. This approach also opens up the possibility of tuning their height and growth angle with respect to the substrate, exhibiting potential applicability in the design of 3D superconducting devices.

Forward volume magnetoacoustic spin wave excitation with micron-scale spatial resolution

The interaction between surface acoustic waves (SAWs) and spin waves (SWs) in a piezoelectric-magnetic thin film heterostructure yields potential for the realization of novel microwave devices and applications in magnonics. In the present work, we characterize magnetoacoustic waves in three adjacent magnetic micro-stripes made from CoFe + Ga, CoFe, and CoFe + Pt with a single pair of tapered interdigital transducers (TIDTs). The magnetic micro-stripes were deposited by focused electron beam-induced deposition and focused ion beam-induced deposition direct-writing techniques. The transmission characteristics of the TIDTs are leveraged to selectively address the individual micro-stripes. Here, the external magnetic field is continuously rotated out of the plane of the magnetic thin film and the forward volume SW geometry is probed with the external magnetic field along the film normal. Our experimental findings are well explained by an extended phenomenological model based on a modified Landau–Lifshitz–Gilbert approach that considers SWs with nonzero wave vectors. Magnetoelastic excitation of forward volume SWs is possible because of the vertical shear strain ɛxz of the Rayleigh-type SAW.

Superconducting Materials and Devices Grown by Focused Ion and Electron Beam Induced Deposition.

Since its discovery in 1911, superconductivity has represented an equally inciting and fascinating field of study in several areas of physics and materials science, ranging from its most fundamental theoretical understanding, to its practical application in different areas of engineering. The fabrication of superconducting materials can be downsized to the nanoscale by means of Focused Ion/Electron Beam Induced Deposition: nanopatterning techniques that make use of a focused beam of ions or electrons to decompose a gaseous precursor in a single step. Overcoming the need to use a resist, these approaches allow for targeted, highly-flexible nanopatterning of nanostructures with lateral resolution in the range of 10 nm to 30 nm. In this review, the fundamentals of these nanofabrication techniques are presented, followed by a literature revision on the published work that makes use of them to grow superconducting materials, the most remarkable of which are based on tungsten, niobium, molybdenum, carbon, and lead. Several examples of the application of these materials to functional devices are presented, related to the superconducting proximity effect, vortex dynamics, electric-field effect, and to the nanofabrication of Josephson junctions and nanoSQUIDs. Owing to the patterning flexibility they offer, both of these techniques represent a powerful and convenient approach towards both fundamental and applied research in superconductivity.

Cryo-Focused Ion Beam-Induced Deposition of Tungsten–Carbon Nanostructures Using a Thermoelectric Plate

Focused Ion Beam-Induced Deposition (FIBID) is a single-step nanopatterning technique that applies a focused beam of ions to induce the decomposition of a gaseous precursor. The processing rate of FIBID increases by two orders of magnitude when the process is performed at cryogenic temperatures (Cryo-FIBID): the precursor forms a condensed layer on the surface of the cooled substrate, greatly enhancing the amount of material available for decomposition. Cryo-FIBID has been achieved so far by making use of liquid nitrogen-based cooling circuits, which require the passage of a flowing gas as a cooling agent. Here, the Cryo-FIBID of the W(CO)6 precursor is performed using a coolant-free thermoelectric plate utilizing the Peltier effect. Performed at −60 ∘C, the procedure yields a W–C-based material with structural and electrical properties comparable to those of its counterpart grown in coolant-based Cryo-FIBID. The use of the thermoelectric plate significantly reduces the vibrations and sample drift induced by the flow of passing coolant gas and allows for the fabrication of similar nanostructures. In summary, the reported process represents a further step towards the practical implementation of the Cryo-FIBID technique, and it will facilitate its use by a broader research community.

Charged Particle-Induced Surface Reactions of Organometallic Complexes as a Guide to Precursor Design for Electron- and Ion-Induced Deposition of Nanostructures.

Focused electron beam-induced deposition (FEBID) and focused ion beam-induced deposition (FIBID) are direct-write fabrication techniques that use focused beams of charged particles (electrons or ions) to create 3D metal-containing nanostructures by decomposing organometallic precursors onto substrates in a low-pressure environment. For many applications, it is important to minimize contamination of these nanostructures by impurities from incomplete ligand dissociation and desorption. This spotlight on applications describes the use of ultra high vacuum surface science studies to obtain mechanistic information on electron- and ion-induced processes in organometallic precursor candidates. The results are used for the mechanism-based design of custom precursors for FEBID and FIBID.

Critical current modulation induced by an electric field in superconducting tungsten-carbon nanowires

The critical current of a superconducting nanostructure can be suppressed by applying an electric field in its vicinity. This phenomenon is investigated throughout the fabrication and electrical characterization of superconducting tungsten-carbon (W-C) nanostructures grown by Ga^+ focused ion beam induced deposition (FIBID). In a 45 nm-wide, 2.7 upmu m-long W-C nanowire, an increasing side-gate voltage is found to progressively reduce the critical current of the device, down to a full suppression of the superconducting state below its critical temperature. This modulation is accounted for by the squeezing of the superconducting current by the electric field within a theoretical model based on the Ginzburg–Landau theory, in agreement with experimental data. Compared to electron beam lithography or sputtering, the single-step FIBID approach provides with enhanced patterning flexibility and yields nanodevices with figures of merit comparable to those retrieved in other superconducting materials, including Ti, Nb, and Al. Exhibiting a higher critical temperature than most of other superconductors, in which this phenomenon has been observed, as well as a reduced critical value of the gate voltage required to fully suppress superconductivity, W-C deposits are strong candidates for the fabrication of nanodevices based on the electric field-induced superconductivity modulation.

Superconducting properties of in-plane W-C nanowires grown by He+ focused ion beam induced deposition

Focused ion beam induced deposition (FIBID) is a nanopatterning technique that uses a focused beam of charged ions to decompose a gaseous precursor. So far, the flexible patterning capabilities of FIBID have been widely exploited in the fabrication of superconducting nanostructures, using the W(CO)6 precursor mostly in combination with a focused beam of Ga+ ions. Here, the fabrication and characterization of superconducting in-plane tungsten-carbon (W-C) nanostructures by He+ FIBID of the W(CO)6 precursor is reported. A patterning resolution of 10 nm has been achieved, which is virtually unattainable for Ga+ FIBID. When the nanowires are patterned with widths of 20 nm and above, the deposited material is superconducting below 3.5–4 K. In addition, nanowires with widths of 60 and 90 nm have been found to sustain long-range controlled nonlocal superconducting vortex transfer along 3 μm. Overall, these findings strengthen the capabilities of He+ FIBID of W-C in the growth and patterning of in-plane superconducting nanodevices.

Photodetecting properties of single CuO\u2013ZnO core\u2013shell nanowires with p\u2013n radial heterojunction

CuO–ZnO core–shell radial heterojunction nanowire arrays were obtained by a simple route which implies two cost-effective methods: thermal oxidation in air for preparing CuO nanowire arrays, acting as a p-type core and RF magnetron sputtering for coating the surface of the CuO nanowires with a ZnO thin film, acting as a n-type shell. The morphological, structural, optical and compositional properties of the CuO–ZnO core–shell nanowire arrays were investigated. In order to analyse the electrical and photoelectrical properties of the metal oxide nanowires, single CuO and CuO–ZnO core–shell nanowires were contacted by employing electron beam lithography (EBL) and focused ion beam induced deposition (FIBID). The photoelectrical properties emphasize that the p–n radial heterojunction diodes based on single CuO–ZnO core–shell nanowires behave as photodetectors, evidencing a time-depending photoresponse under illumination at 520 nm and 405 nm wavelengths. The performance of the photodetector device was evaluated by assessing its key parameters: responsivity, external quantum efficiency and detectivity. The results highlighted that the obtained CuO–ZnO core–shell nanowires are emerging as potential building blocks for a next generation of photodetector devices.

Optimization of Pt-C Deposits by Cryo-FIBID: Substantial Growth Rate Increase and Quasi-Metallic Behaviour.

The Focused Ion Beam Induced Deposition (FIBID) under cryogenic conditions (Cryo-FIBID) technique is based on obtaining a condensed layer of precursor molecules by cooling the substrate below the condensation temperature of the gaseous precursor material. This condensed layer is irradiated with ions according to a desired pattern and, subsequently, the substrate is heated above the precursor condensation temperature, revealing the deposits with the shape of the exposed pattern. In this contribution, the fast growth of Pt-C deposits by Cryo-FIBID is demonstrated. Here, we optimize various parameters of the process in order to obtain deposits with the lowest-possible electrical resistivity. Optimized ~30 nm-thick Pt-C deposits are obtained using ion irradiation area dose of 120 μC/cm2 at 30 kV. This finding represents a substantial increment in the growth rate when it is compared with deposits of the same thickness fabricated by standard FIBID at room temperature (40 times enhancement). The value of the electrical resistivity in optimized deposits (~4 × 104 µΩ cm) is suitable to perform electrical contacts to certain materials. As a proof of concept of the potential applications of this technology, a 100 µm × 100 µm pattern is carried out in only 43 s of ion exposure (area dose of 23 μC/cm2), to be compared with 2.5 h if grown by standard FIBID at room temperature. The ion trajectories and the deposit composition have been simulated using a binary-collision-approximation Monte Carlo code, providing a solid basis for the understanding of the experimental results.

Structural characterization and continuous cellular automata simulation of micro structures by focused Ga ion beam induced deposition process

Focused ion beam induced deposition (FIBID) is a high-resolution micro/nano fabrication technique with the injection of precursor gas to produce complex three-dimensional structures, which can be used to construct nanodevices. Due to the complex interaction between precursor gas, incident ions, and the substrate, the morphology of deposition structure dramatically depends on the process parameters. In this paper, based on the Continuous Cellular Automata (CCA) and the extended precursor molecule diffusion model (EPMDM), the effects of different process parameters on the final deposition morphology, are systematically studied. The experimental and theoretical work explores the relationship between the characterization of the deposition structure and process parameters. Considering the variation of diffusion effect intensity, the diffusion coefficient matrix decaying with the structure height is established to calculate the contribution of diffusion effect more precisely, which can also explain the non-uniform growth of deposition structure in the FIBID process. The vacuum surface cells (VSCs) and solid surface cells (SSCs) are recognized for deposition and sputtering respectively in the CCA, so as to trace the dynamic deposition contour, and reproduce the coexistence of deposition and sputtering phenomena. In order to verify the proposed CCA simulation model, micro pillar array and other structures are fabricated by focused Ga ion beam induced C9H16Pt precursor gas. The experimental and simulation results show that the proposed model can well simulate the morphology of deposition structures under a wide range of process parameters of dwell time, refresh time, ion beam current and pixel overlap. Therefore, the model can provide a good prediction method for parameter optimization of focused Ga ion beam induced deposition process.

Direct Write of 3D Nanoscale Mesh Objects with Platinum Precursor via Focused Helium Ion Beam Induced Deposition.

The next generation optical, electronic, biological, and sensing devices as well as platforms will inevitably extend their architecture into the 3rd dimension to enhance functionality. In focused ion beam induced deposition (FIBID), a helium gas field ion source can be used with an organometallic precursor gas to fabricate nanoscale structures in 3D with high-precision and smaller critical dimensions than focused electron beam induced deposition (FEBID), traditional liquid metal source FIBID, or other additive manufacturing technology. In this work, we report the effect of beam current, dwell time, and pixel pitch on the resultant segment and angle growth for nanoscale 3D mesh objects. We note subtle beam heating effects, which impact the segment angle and the feature size. Additionally, we investigate the competition of material deposition and sputtering during the 3D FIBID process, with helium ion microscopy experiments and Monte Carlo simulations. Our results show complex 3D mesh structures measuring ~300 nm in the largest dimension, with individual features as small as 16 nm at full width half maximum (FWHM). These assemblies can be completed in minutes, with the underlying fabrication technology compatible with existing lithographic techniques, suggesting a higher-throughput pathway to integrating FIBID with established nanofabrication techniques.

Mechanical Properties of 3D Nanostructures Obtained by Focused Electron/Ion Beam-Induced Deposition: A Review.

This article reviews the state-of-the -art of mechanical material properties and measurement methods of nanostructures obtained by two nanoscale additive manufacturing methods: gas-assisted focused electron and focused ion beam-induced deposition using volatile organic and organometallic precursors. Gas-assisted focused electron and ion beam-induced deposition-based additive manufacturing technologies enable the direct-write fabrication of complex 3D nanostructures with feature dimensions below 50 nm, pore-free and nanometer-smooth high-fidelity surfaces, and an increasing flexibility in choice of materials via novel precursors. We discuss the principles, possibilities, and literature proven examples related to the mechanical properties of such 3D nanoobjects. Most materials fabricated via these approaches reveal a metal matrix composition with metallic nanograins embedded in a carbonaceous matrix. By that, specific material functionalities, such as magnetic, electrical, or optical can be largely independently tuned with respect to mechanical properties governed mostly by the matrix. The carbonaceous matrix can be precisely tuned via electron and/or ion beam irradiation with respect to the carbon network, carbon hybridization, and volatile element content and thus take mechanical properties ranging from polymeric-like over amorphous-like toward diamond-like behavior. Such metal matrix nanostructures open up entirely new applications, which exploit their full potential in combination with the unique 3D additive manufacturing capabilities at the nanoscale.

Continuous cellular automaton simulation of focused ion beam-induced deposition for nano structures

With the assistance of a gas injection system, focused ion beam-induced deposition (FIBID) can be realized to fabricate complicated three-dimensional structures in nanoscale. The growth rate of the deposited structure depends on the flux of precursor gas and incident ions. In this study, a Continuous Cellular Automaton (CCA) model is put forward to simulate the FIBID process, with four rules established to initiate and dominate the interface evolution, which can calculate the deposited structure profile under different fabrication conditions. In this model, the sputtering and diffusion effects are taken into account to establish a more accurate relationship between the deposition rate and precursor gas flux based on the continuous model, and the influences imposed by precursor gas and incident ions are clarified. In order to verify the precursor gas distribution and the growth mechanism of the FIBID, experiments are carried out with different local precursor gas flux on the substrate surface with a 7 pA and 30 keV Ga ions, using C9H16Pt as the precursor gas. The experimental and simulation results indicate that the CCA model features a high accuracy in predicting the deposited structure profile, and prove that the proposed model can be utilized in fabrication parameters optimization.

Novel technology for fabrication of probe tips for SPM using focused ion beam-induced deposition method

The results of an experimental study of the fabrication of high aspect probe tips for atomic force microscopy (AFM) and critical dimension AFM (CD AFM) using the focused ion beam (FIB) milling and ion beam induced deposition of carbon are presented. It is shown that the probes formed by the FIB method have a higher resolution of surface scanning and allow studying nanoscale structures without distortion. In this work, a technique for the formation of AFM probes based on the use of a combination of ion-beam milling and ion-induced carbon deposition was developed. Based on the developed technique, high aspect probe with about 8 μm high, with a tip radius of about 40 nm and an aspect ratio of 30:1, were fabricated. A probe for CD AFM was also formed using FIB-induced deposition of carbon with about 320 nm of flare. The results obtained in the study can be used in the development of technological processes for the manufacturing and modification of special probes for AFM, including probes CD-AFM. The paper shows the possibility of forming the tip of the probes for specialized tasks of nanodiagnostics and nanometrology. The proposed technology allows reducing the artefacts of scanning probe microscopy and improving the adequacy of the results of AFM studies.

Quartz tuning fork mass change sensing for FIB/SEM technology

In this paper we present a metrological method for determination of mass density of focused ion beam induced deposition (FIBID) materials using quartz tuning fork (QTF) mass change sensors. Dimension and density determination of FIBID deposited nanostructures is necessary to develop and reliable and repeatable microfabribrication technology of the highest versatility. The proposed metrological methodology allows to determine mass change with 5 pg resolution and accuracy below 5 % if density is considered. The described method is suitable for precise FIBID precursor parameters determination conducted during the deposition as actuation and signal read-out of the applied QTF can be performed electrically. High accuracy, resolution and stability are ensured due to excellent properties of quartz forming the sensor structure.

Comparison between Focused Electron/Ion Beam-Induced Deposition at Room Temperature and under Cryogenic Conditions.

In this contribution, we compare the performance of Focused Electron Beam-induced Deposition (FEBID) and Focused Ion Beam-induced Deposition (FIBID) at room temperature and under cryogenic conditions (the prefix “Cryo” is used here for cryogenic). Under cryogenic conditions, the precursor material condensates on the substrate, forming a layer that is several nm thick. Its subsequent exposure to a focused electron or ion beam and posterior heating to 50 °C reveals the deposit. Due to the extremely low charge dose required, Cryo-FEBID and Cryo-FIBID are found to excel in terms of growth rate, which is typically a few hundred/thousand times higher than room-temperature deposition. Cryo-FIBID using the W(CO)6 precursor has demonstrated the growth of metallic deposits, with resistivity not far from the corresponding deposits grown at room temperature. This paves the way for its application in circuit edit and the fast and direct growth of micro/nano-electrical contacts with decreased ion damage. The last part of the contribution is dedicated to the comparison of these techniques with other charge-based lithography techniques in terms of the charge dose required and process complexity. The comparison indicates that Cryo-FIBID is very competitive and shows great potential for future lithography developments.