Gallium Focused Ion Beam Research Articles

Rubidium and Cesium Ion-Induced Electron and Ion Signals for Scanning Ion Microscopy Applications.

Scanning ion microscopy applications of novel focused ion beam (FIB) systems based on ultracold rubidium (Rb) and cesium (Cs) atoms were investigated via ion-induced electron and ion yields. Results measured on the Rb+ and Cs+ FIB systems were compared with results from commercially available gallium (Ga+) FIB systems to verify the merits of applying Rb+ and Cs+ for imaging. The comparison shows that Rb+ and Cs+ have higher secondary electron (SE) yields on a variety of pure element targets than Ga+, which implies a higher signal-to-noise ratio can be achieved for the same dose in SE imaging using Rb+/Cs+ than Ga+. In addition, analysis of the ion-induced ion signals reveals that secondary ions dominate Cs+ induced ion signals while the Rb+/Ga+ induced signals contain more backscattered ions.

Wavelike Periodic Structures on the Silicon Surface Initiated by Irradiation with a Focused Gallium Ion Beam

Wavelike Periodic Structures on the Silicon Surface Initiated by Irradiation with a Focused Gallium Ion Beam

Plasmonic slanted slit gratings for efficient through-substrate light-plasmon coupling and sensing

We present an experimental study of plasmonic slanted slit gratings (PSSGs) designed to achieve directional coupling between an incident light beam and surface plasmon polaritons (SPPs) propagating along the surface of the structure. We also investigate mirrored PSSG pairs interconnected by a plasmonic slab waveguide. The structures are fabricated using direct milling by a gallium focused ion beam (FIB). In a mirrored pair arrangement, the first PSSG couples a perpendicularly-incident light beam to SPPs propagating in one direction along the waveguide, while the second PSSG decouples SPPs to perpendicularly-emerging light. This configuration shows promise for sensing applications due to the high sensitivity of the excited SPPs to changes in the refractive index of the bounding medium, and the separation of the optics from the fluidics by the substrate. The design also exhibits robustness to fabrication tolerances. The optical characteristics and sensing potential are investigated theoretically and experimentally, highlighting its potential for a wide range of applications.

Roadmap for focused ion beam technologies

The focused ion beam (FIB) is a powerful tool for fabrication, modification, and characterization of materials down to the nanoscale. Starting with the gallium FIB, which was originally intended for photomask repair in the semiconductor industry, there are now many different types of FIB that are commercially available. These instruments use a range of ion species and are applied broadly in materials science, physics, chemistry, biology, medicine, and even archaeology. The goal of this roadmap is to provide an overview of FIB instrumentation, theory, techniques, and applications. By viewing FIB developments through the lens of various research communities, we aim to identify future pathways for ion source and instrumentation development, as well as emerging applications and opportunities for improved understanding of the complex interplay of ion–solid interactions. We intend to provide a guide for all scientists in the field that identifies common research interest and will support future fruitful interactions connecting tool development, experiment, and theory. While a comprehensive overview of the field is sought, it is not possible to cover all research related to FIB technologies in detail. We give examples of specific projects within the broader context, referencing original works and previous review articles throughout.

High-Tc Josephson Junction Arrays for THz Applications

High-T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> superconductors (HTS) like yttrium barium copper oxide (YBa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7-x</sub> ) pave the way towards readily available and precise voltage standards at liquid nitrogen temperatures. They can be driven by terahertz radiation, thus achieving higher output voltages with a significantly reduced junction count. The reduced effort in cooling also simplifies the overall application. The use of a gallium focused ion beam (Ga-FIB) represents a promising method to tailor the geometry of Josephson junctions after conventional patterning of an array to tune the junction parameters individually. In this work, we present a Josephson junction array made from the HTS YBa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7-x</sub> based on grain-boundary Josephson junctions. The junction parameters are investigated and afterwards the influence of the Ga-FIB on the junctions is examined. This serves as an important step to show the suitability of this process for HTS voltage standards. Furthermore, the high frequency properties of the array and the associated Shapiro steps are characterized in the terahertz range. This technique represents an important step towards versatile HTS voltage standards.

The reduction of FIB damage on cryo-lamella by lowering energy of ion beam revealed by a quantitative analysis

Focused ion beam (FIB) is widely used for thinning frozen cells to produce lamellae for cryo-electron microscopy imaging and for protein structures study invivo. However, FIB damages the lamellae and a quantitative experimental analysis of the damage is lacking. We used a 30-keV gallium FIB to prepare lamellae of a highly concentrated icosahedral virus sample. The viruses were grouped according to their distance from the surface of lamellae and reconstructed. Damage to the approximately 20-nm-thick outermost lamella surface was similar to that from exposure to 16 e-/Å2 in a 300-kV cryo-electron microscope at high-resolution range. The damage was negligible at a depth beyond 50nm, which was reduced to 30nm if 8-keV Ga+ was used during polishing. We designed extra steps in the reconstruction refinement to maximize undamaged signals and increase the resolution. The results demonstrated that low-energy beam polishing was essential for high-quality thinner lamellae.

Understanding the impact of heavy ions and tailoring the optical properties of large-area monolayer WS2 using focused ion beam

Focused ion beam (FIB) is an effective tool for precise nanoscale fabrication. It has recently been employed to tailor defect engineering in functional nanomaterials such as two-dimensional transition metal dichalcogenides (TMDCs), providing desirable properties in TMDC-based optoelectronic devices. However, the damage caused by the FIB irradiation and milling process to these delicate, atomically thin materials, especially in extended areas beyond the FIB target, has not yet been fully characterised. Understanding the correlation between lateral ion beam effects and optical properties of 2D TMDCs is crucial in designing and fabricating high-performance optoelectronic devices. In this work, we investigate lateral damage in large-area monolayer WS2 caused by the gallium focused ion beam milling process. Three distinct zones away from the milling location are identified and characterised via steady-state photoluminescence (PL) and Raman spectroscopy. The emission in these three zones have different wavelengths and decay lifetimes. An unexpected bright ring-shaped emission around the milled location has also been revealed by time-resolved PL spectroscopy with high spatial resolution. Our findings open up new avenues for tailoring the optical properties of TMDCs by charge and defect engineering via focused ion beam lithography. Furthermore, our study provides evidence that while some localised damage is inevitable, distant destruction can be eliminated by reducing the ion beam current. It paves the way for the use of FIB to create nanostructures in 2D TMDCs, as well as the design and realisation of optoelectrical devices on a wafer scale.

Simulation of Silicon Carbide Sputtering by a Focused Gallium Ion Beam

Simulation of Silicon Carbide Sputtering by a Focused Gallium Ion Beam

Hot Carrier-Induced Nonlinear Photoluminescence in a Thin Indium Tin Oxide Layer Patterned by Ga Ion Beam Milling

This paper explores the nonlinear photoluminescence emitted by indium tin oxide (ITO) thin layers patterned by focused gallium ion beam milling. Using tightly focused near-infrared femtosecond pulsed laser excitation, a broad up-converted luminescence spectrum spanning the visible is detected. The intensity of the luminescence follows a nonmonotonous relationship with milling doses and can be related to the modification of the ITO electronic band structure by the implantation of Ga ions. The shape and the power dependence of the spectrum share strong similarities with those of nonlinear photoluminescence arising from metals. The results are consistent with a nonlinear process originating from the radiative decay of photogenerated hot carriers. The thermal coefficient relating the carrier temperature to the laser intensity is determined as a function of milling dose.

Micromechanical properties of low-carbon martensitic stainless steel by microtensile experiments

This paper presents a detailed experimental approach to extract the critical resolved shear stress (CRSS) and the saturation stress of the elementary constituents of the microstructure of quenched S41500 martensitic stainless steel by conducting various microscopy observations and microtensile testing. To the authors' knowledge, the direct extraction of micromechanical properties of a single martensite variant by tensile testing has never been performed. However, the literature does propose studies that measured the mechanical properties of the bulk or small volumes containing a few variants. In this work, a particular attention is dedicated to the preparation of the specimens from the macro to the microscale, where final machining of test specimens was made using a Gallium Focused Ion Beam (Ga-FIB). In the present work, the CRSSs of {110}, {211} and {123} plane-related slip systems were directly measured. The post-experiment analysis showed no significant difference between the slip resistance of those planes. To relate this effort with previous work, a comparison with results from the literature was made using a similar testing procedure in lath martensite, revealing similar values of CRSS. The slip resistance saturation was also measured on different slip systems, and the data suggest a very similar hardening behavior for most of the samples tested. Finally, cross-slip remains, in this alloy, a very potent mechanism to reduce the strain hardening that can arise from clusters of nanoparticles observed by TEM.

New insight into anodization of aluminium with focused ion beam pre-patterning

The self-ordered anodic aluminium oxide (AAO) structure consists of micron-scale domains—defect-free areas with a hexagonal arrangement of pores. A substantial increase in domain size is possible solely by pre-patterning the aluminium surface in the form of a defect-free hexagonal array of concaves, which guide the pore growth during subsequent anodization. Among the numerous pre-patterning techniques, direct etching by focused gallium ion beam (Ga FIB) allows the preparation of AAO with a custom-made geometry through precise control of the irradiation positions, beam energy, and ion dosage. The main drawback of the FIB approach includes gallium contamination of the aluminium surface. Here, we propose a multi-step anodizing procedure to prevent gallium incorporation into the aluminium substrate. The suggested approach successfully covers a wide range of AAO interpore distances from 100 to 500 nm. In particular, anodization of FIB pre-patterned aluminium in 0.1 M phosphoric acid at 195 V to prepare AAO with the interpore distance of about 500 nm was demonstrated for the first time. The quantification of the degree of pore ordering reveals the fraction of pores in hexagonal coordination above 96% and the in-plane mosaicity below 3° over an area of about 1000 μm2. Large-scale defect-free AAO structures are promising for creating photonic crystals and hyperbolic metamaterials with distinct functional properties.

Selective growth of graphene films on gallium-focused ion beam irradiated domains

Graphene, a single layer of carbon atoms tightly bound in a hexagonal honeycomb lattice to form a two-dimensional lattice, is a very interesting material with promising electronic, optical, chemical, and mechanical applicative potential [Geim and Novoselov, Nat. Mater. 6, 183 (2007)]. The properties of graphene make it suitable for a wide range of applications; however, its applicative future still depends on large scale technologies capable to robustly and reproducibly transfer its outstanding intrinsic properties into devices or complex structures. It must be recognized that a crucial technological problem, that still inhibits the applicability of high quality graphene material properties, is related to the patterning of this material using traditional top down instruments and lithographical methods. In this work, we will detail our investigations on applying a precise 30 keV Ga+ ion irradiation to selectively shape and modify a copper precursor surface for promoting the local growth of graphene surface domains. The morphology of these domains is investigated using scanning tunneling microscopy and spectroscopy to probe simultaneously the structural and the electronic properties at the atomic scale of the graphene films.

Demonstration of multiple quantum interference and Fano resonance realization in far-field from plasmonic nanostructure in Er3+-doped tellurite glass

It is crucial to control the tuning and improve the emission of a quantum emitter at the nanoscale. We report multiple Fano resonances in metallic nanostructures on an Er3+-doped tellurite glass. Periodic nanoslits were fabricated with a focused gallium ion beam on a gold thin film deposited on the tellurite glass. Is proposed a coupling function with Fano line-shape form, and the asymmetric parameter q for each resonance wavelength in the 515 to 535 nm region was calculated. This asymmetric resonance effect is a consequence of the quantum interaction between the continuum state, generated in the nanostructure, and the Stark splits of the ^2H_{11/2} state.

Characterization and simulation of sputtering etched profile by focused gallium ion beam on GaN substrate

With the continuous development of manufacturing technology of micro/nano devices based on GaN, focused gallium ion beam has become a momentous method for machining complex GaN structures. Therefore, this study focuses on the characterization and simulation of sputtering etched profile by Ga FIB on GaN substrate. First, the profile characterization experiments are carried out to analyze the influence of ion dose, dwelling time, and scan area, and the results reflect that the sputtering etched regularity on GaN substrate differs from that on Si substrate, especially in redeposition effect, milling rate, and droplet phenomenon. In addition, the forming mechanism of droplet phenomenon is discussed, and the milling experiments are conducted to research the droplets avoidance method, which shows that the appearance of droplets is impacted by ion dose and dwelling time. Finally, the sputtering yield of GaN under focused gallium ion beam is measured and sorted, and the simulation program is developed based on continuous cellular automaton (CCA) model. This work can provide a guidance for the further application of GaN-based materials.

Features of the Formation of Ripple Structures on the Surface of Silicon under Irradiation with a Focused Gallium Ion Beam

Features of the Formation of Ripple Structures on the Surface of Silicon under Irradiation with a Focused Gallium Ion Beam

Effect of wet chemical treatment on the properties of GaAs FIB-modified surface

We present the results of studies of the effect of wet chemical treatment on the properties of a GaAs surface modified by a gallium focused ion beam. Our studies based on results of AFM, KpAFM and Raman spectroscopy measurements have shown that, during wet chemical treatment, the damaged areas disappear completely in the case of low accelerating voltages and small doses of ions. At the same time, large accelerating voltages lead to the formation of extended damaged regions, the complete removal of which requires a longer treatment or additional processing.

Annealing treatment of focused gallium ion beam processing of SERS gold substrate

Raman spectroscopy is a type of inelastic scattering spectroscopy that is widely used in determining and analyzing molecular structure. It also has a number of practical applications in evaluating food safety, medicine, and forensics. The Raman spectral signal is weak, but the development of the surface-enhanced Raman scattering (SERS) technique has overcome this problem and led to further developments in Raman spectroscopy. This paper describes a fundamental study of the use of focused ion beam (FIB) direct writing for preparing gold substrates for SERS. Molecular dynamics and Monte Carlo simulation methods are used to investigate the damage induced by gallium ion implantation of a gold substrate. Based on characterization by x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy, the mechanism by which ion implantation and annealing influence the damage induced by a gallium FIB is analyzed. After annealing at 350 °C, a mixture of metallic gallium, its oxide Ga2O3 conforming to the stoichiometric ratio, and its sub-stable oxide (Ga2Ox) in sub-stoichiometric ratio precipitated on the surface are detected by XPS. Annealing treatment can effectively reduce the effect of gallium ion implantation on a SERS substrate fabricated by FIB direct writing.

Metallic Contaminant Detection in Liquids using a High-Tc RF-SQUID

We have developed a system using high-temperature radio frequency superconducting quantum interference device (RF-SQUID) for detecting metallic contaminants in the liquid component of a lithium-ion battery. Although we have executed detection experiments using a simulated system without liquid in the past[1], we have developed a new system to inspect real liquid components. Small cylindrical metallic contaminant samples were fabricated using a gallium-focused ion beam to evaluate the detection performance. Tap water containing the metallic contaminant sample was poured into the tube using a pump, and the magnetic signal of the contaminant matter was detected using the RF-SQUID. Among the tested small metallic contaminant samples, the volume of a minimum detectable metallic contaminant was evaluated to be 2 × 104 μm3, which corresponded to that of a spherical sample with a diameter of 33 μm and a sensitivity of a signal-to-noise ratio of more than three. Moreover, the dependence of the detected signal strength on the volume of the metallic contaminant samples is discussed here.

Morphology and formation of crystalline leucine microparticles from a co-solvent system using multi-orifice monodisperse spray drying

The purpose of this study was twofold: to investigate leucine crystallization kinetics in co-solvent spray drying for a deeper understanding of the morphology and formation process of spray-dried crystalline particles, and also to develop multi-orifice plates using gallium focused ion beam milling in order to increase the production rate of monodisperse spray drying. A monodisperse spray drying technique using a vibrating orifice atomizer equipped with a gallium focused ion beam-manufactured dual-orifice plate was used to produce model particles in this study. The dual-orifice plate achieved an average production rate of 23.8 ± 2.0 mg/hr for the model particles, which allowed sufficient production of monodisperse powders for microscopic and spectroscopic analysis as well as fragility testing, within a reasonable spray drying time period. Leucine was dissolved in a water-ethanol co-solvent at ratios of 0.25/0.75 w/w, 0.5/0.5 w/w, and 1/0 w/w, and then spray dried at inlet temperatures of 20, 40, and 80 °C. Crystallinity of the spray-dried particles was confirmed by Raman spectroscopy. Numerical models were used to predict the crystallization and drying kinetics for the different co-solvent ratios and drying temperatures. Increasing the time available for crystallization correlated qualitatively with a larger crystal size. Changes in particle morphology affected the fragility of the particles, as illustrated in electron microscope images. This work highlights the importance of controlling crystal size and particle morphology via solvent environment and drying temperature in the design and manufacture of microparticles for desired powder properties.Copyright © 2021 American Association for Aerosol Research

Fabrication of HTS Low-Noise Nanobridge Josephson Junction by Gallium FIB

High-temperature superconductor (HTS) Josephson junctions (JJs) are primarily based on artificial grain boundaries. Bi-crystal JJs are typically utilized in HTS superconducting quantum interference devices (SQUIDs). However, the performances of bi-crystal JJs depend significantly on the quality of the interface at the junction. In this study, we investigate a method for forming nanobridge JJs via gallium focused ion beam (FIB) irradiation. A 100-nm-thick YBa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7-</sub> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">δ</sub> was deposited on an MgO (100) substrate via pulsed laser deposition. An additional 20-nm-thick Au layer, which serves as a protection layer preventing ion damage during alignment, was deposited in situ. HTS microchannels with a width of 4 μm were defined via photolithography and argon ion milling. The HTS microchannel widths are decreased via FIB line scans to create nanobridges. The JJs are fabricated using two types of HTS thin films, in which one has a higher critical current density (J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</sub> ) that the other. The fabrication process using the gallium FIB was optimized and nanobridges with a junction width of 80 nm were prepared. As a result, a better with higher J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</sub> (5 MA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) HTS films allowed for making junctions exhibiting up to five Shapiro steps at 77 K.