Showing papers on "Focused ion beam published in 2015"

Nanoscale 3D Chiral Plasmonic Helices with Circular Dichroism at Visible Frequencies

Abstract: The nanoscaling of metamaterial structures represents a technological challenge toward their application in the optical frequency range. In this work we demonstrate tailored chiro-optical effects in plasmonic nanohelices, by a fabrication process providing a nanometer scale control on geometrical features, that leads to a fine tuning of operation band even in the visible range. Helicoidal 3D nanostructures have been prototyped by a bottom-up approach based on focused ion and electron beam induced deposition, investigating resolution limits, growth control and 3D proximity effects as a function of the interactions between writing beam and deposition environment. The fabricated arrays show chiro-optical properties at the optical frequencies and extremely high operation bandwidth tailoring dependent on the dimensional features of these 3D nanostructures: with the focused ion beam we obtained a broadband polarization selection of about 600 nm and maximum dissymmetry factor up to 40% in the near-infrared regio...

Fabrication of high-Q lithium niobate microresonators using femtosecond laser micromachining

Abstract: We report on fabrication of high-Q lithium niobate (LN) whispering-gallery-mode (WGM) microresonators suspended on silica pedestals by femtosecond laser direct writing followed by focused ion beam (FIB) milling. The micrometer-scale (diameter ~82 μm) LN resonator possesses a Q factor of ~2.5 × 105 around 1550 nm wavelength. The combination of femtosecond laser direct writing with FIB enables high-efficiency, high-precision nanofabrication of high-Q crystalline microresonators.

Focused ion beams in biology

Abstract: A quiet revolution is under way in technologies used for nanoscale cellular imaging. Focused ion beams, previously restricted to the materials sciences and semiconductor fields, are rapidly becoming powerful tools for ultrastructural imaging of biological samples. Cell and tissue architecture, as preserved in plastic-embedded resin or in plunge-frozen form, can be investigated in three dimensions by scanning electron microscopy imaging of freshly created surfaces that result from the progressive removal of material using a focused ion beam. The focused ion beam can also be used as a sculpting tool to create specific specimen shapes such as lamellae or needles that can be analyzed further by transmission electron microscopy or by methods that probe chemical composition. Here we provide an in-depth primer to the application of focused ion beams in biology, including a guide to the practical aspects of using the technology, as well as selected examples of its contribution to the generation of new insights into subcellular architecture and mechanisms underlying host-pathogen interactions.

Cryo-focused Ion Beam Sample Preparation for Imaging Vitreous Cells by Cryo-electron Tomography

Abstract: Cryo-electron tomography (CET) is a well-established technique for imaging cellular and molecular structures at sub-nanometer resolution. As the method is limited to samples that are thinner than 500 nm, suitable sample preparation is required to attain CET data from larger cell volumes. Recently, cryo-focused ion beam (cryo-FIB) milling of plunge-frozen biological material has been shown to reproducibly yield large, homogeneously thin, distortion-free vitreous cross-sections for state-of-the-art CET. All eukaryotic and prokaryotic cells that can be plunge-frozen can be thinned with the cryo-FIB technique. Together with advances in low-dose microscopy, this has shifted the frontiers of in situ structural biology. In this protocol we describe the typical steps of the cryo-FIB technique, starting with fully grown cell cultures. Three recently investigated biological samples are given as examples.

Crystal Morphologies of Organolead Trihalide in Mesoscopic/Planar Perovskite Solar Cells.

Abstract: The crystal morphology of organolead trihalide perovskite (OTP) light absorbers can have profound influence on the perovskite solar cells (PSCs) performance. Here we have used a combination of conventional transmission electron microscopy (TEM) and high-resolution TEM (HRTEM), in cross-section and plan-view, to characterize the morphologies of a solution-processed OTP (CH3NH3PbI3 or MAPbI3) within mesoporous TiO2 scaffolds and within capping and planar layers. Studies of TEM specimens prepared with and without the use of focused ion beam (FIB) show that FIBing is a viable method for preparing TEM specimens. HRTEM studies, in conjunction with quantitative X-ray diffraction, show that MAPbI3 perovskite within mesoporous TiO2 scaffold has equiaxed grains of size 10–20 nm and relatively low crystallinity. In contrast, the grain size of MAPbI3 perovskite in the capping and the planar layers can be larger than 100 nm in our PSCs, and the grains can be elongated and textured, with relatively high crystallinity. ...

Toward Two-Dimensional All-Carbon Heterostructures via Ion Beam Patterning of Single-Layer Graphene.

Abstract: Graphene has many claims to fame: it is the thinnest possible membrane, it has unique electronic and excellent mechanical properties, and it provides the perfect model structure for studying materials science at the atomic level. However, for many practical studies and applications the ordered hexagon arrangement of carbon atoms in graphene is not directly suitable. Here, we show that the atoms can be locally either removed or rearranged into a random pattern of polygons using a focused ion beam (FIB). The atomic structure of the disordered regions is confirmed with atomic-resolution scanning transmission electron microscopy images. These structural modifications can be made on macroscopic scales with a spatial resolution determined only by the size of the ion beam. With just one processing step, three types of structures can be defined within a graphene layer: chemically inert graphene, chemically active amorphous 2D carbon, and empty areas. This, along with the changes in properties, gives promise that ...

Electrochemical Deposition and Stripping Behavior of Lithium Metal across a Rigid Block Copolymer Electrolyte Membrane

Abstract: Author(s): Harry, KJ; Liao, X; Parkinson, DY; Minor, AM; Balsara, NP | Abstract: Replacing the conventional graphite anode in rechargeable batteries with lithium metal results in a significant increase in energy density. However, growth of electronically conductive structures, like dendrites, from lithium anodes causes premature battery failure by short circuit. Mechanically rigid electrolytes are thought to promote smooth lithium deposition by increasing the energy required for lithium reduction at regions of high local strain, like a dendrite tip. The study reported herein used X-ray microtomography, Focused Ion Beam (FIB) milling, and Scanning Electron Microscopy (SEM) imaging to investigate the electrochemical stripping and deposition behavior of lithium in symmetric lithium - polymer cells using a rigid polystyrene-b-poly(ethylene oxide) membrane as the electrolyte. In situ experiments show the formation of globular lithium structures that grow to puncture the polymer electrolyte membrane. They form on faceted impurity particles that are initially located at the lithium/electrolyte interface. While the impurities are uniformly distributed throughout the lithium foil in initial images, their relative concentration near the electrolyte changes as lithium is stripped from one electrode and deposited on the other. Notably, the deposited lithium is devoid of faceted impurities. This electrolytic refining of lithium could be used to prepare anodic lithium foils for batteries with improved cycle life.

Focused Electron and Ion Beam Induced Deposition on Flexible and Transparent Polycarbonate Substrates.

Abstract: The successful application of focused electron (and ion) beam induced deposition techniques for the growth of nanowires on flexible and transparent polycarbonate films is reported here. After minimization of charging effects in the substrate, sub-100 nm-wide Pt, W, and Co nanowires have been grown and their electrical conduction is similar compared to the use of standard Si-based substrates. Experiments where the substrate is bent in a controlled way indicate that the electrical conduction is stable up to high bending angles, >50°, for low-resistivity Pt nanowires grown by the ion beam. On the other hand, the resistance of Pt nanowires grown by the electron beam changes significantly and reversibly with the bending angle. Aided by the substrate transparency, a diffraction grating in transmission mode has been built based on the growth of an array of Pt nanowires that shows sharp diffraction spots. The set of results supports the large potential of focused beam deposition as a high-resolution nanolithograp...

Continuum models of focused electron beam induced processing.

Abstract: Focused electron beam induced processing (FEBIP) is a suite of direct-write, high resolution techniques that enable fabrication and editing of nanostructured materials inside scanning electron microscopes and other focused electron beam (FEB) systems. Here we detail continuum techniques that are used to model FEBIP, and release software that can be used to simulate a wide range of processes reported in the FEBIP literature. These include: (i) etching and deposition performed using precursors that interact with a surface through physisorption and activated chemisorption, (ii) gas mixtures used to perform simultaneous focused electron beam induced etching and deposition (FEBIE and FEBID), and (iii) etch processes that proceed through multiple reaction pathways and generate a number of reaction products at the substrate surface. We also review and release software for Monte Carlo modeling of the precursor gas flux which is needed as an input parameter for continuum FEBIP models.

Solid-state additive manufacturing for metallized optical fiber integration

Abstract: The formation of smart, Metal Matrix Composite (MMC) structures through the use of solid-state Ultrasonic Additive Manufacturing (UAM) is currently hindered by the fragility of uncoated optical fibers under the required processing conditions. In this work, optical fibers equipped with metallic coatings were fully integrated into solid Aluminum matrices using processing parameter levels not previously possible. The mechanical performance of the resulting manufactured composite structure, as well as the functionality of the integrated fibers, was tested. Optical microscopy, Scanning Electron Microscopy (SEM) and Focused Ion Beam (FIB) analysis were used to characterize the interlaminar and fiber/matrix interfaces whilst mechanical peel testing was used to quantify bond strength. Via the integration of metallized optical fibers it was possible to increase the bond density by 20–22%, increase the composite mechanical strength by 12–29% and create a solid state bond between the metal matrix and fiber coating; whilst maintaining full fiber functionality.

Single Grain Boundary Break Junction for Suspended Nanogap Electrodes with Gapwidth Down to 1–2 nm by Focused Ion Beam Milling

Abstract: Single grain boundary junctions are used for the fabrication of suspended nanogap electrodes with a gapwidth down to 1-2 nm through the break of such junctions by focused ion beam (FIB) milling. With advantages of stability and no debris, such nanogap electrodes are suitable for single molecular electronic device construction.

An Integrated Method for Upscaling Pore-Network Characterization and Permeability Estimation: Example from the Mississippian Barnett Shale

Abstract: Although pore-network characterization of shale rock systems is being actively investigated, a detailed understanding of the pore network at the nanometer-to-millimeter scale has not been completed. This is because of the technical limitations of collecting and integrating data at the wide spectrum of scales necessary to understand the pore network. Permeability for a micrometer-scale volume can be estimated based on pore-scale modeling for the focused ion beam/scanning electron microscope (FIB/SEM) milled 3D pore network; however, it is not clear how representative this permeability is for larger volumes. In this study, an integrated method employing FIB/SEM, helium ion microscopy, and synchrotron X-ray micro-computed tomography (micro-CT) was developed and applied to a Barnett Shale sample for pore and organic-matter distribution network characterization and upscaling. Organic-matter particle network characterization using synchrotron micro-CT scanning is the key step that bridges the gap between nanometer-scale and macroscopic observations. A conceptual model and an empirical equation were developed for permeability estimation based on FIB/SEM and micro-CT image analysis and mercury intrusion data. Upscaled permeability estimation was produced based on the empirical equation and parameters from the image and mercury intrusion analysis. The resulting permeability values of 2–22 and 0.6–3 nD for parallel and perpendicular to bedding planes, respectively, are comparable to laboratory measurements of the same sample. The proposed technique provides a method for more basic understanding of the pore network and pore-permeability relationship for organic-rich shale samples, and can serve as a basis for further upscaling to core and formation scale.

High temperature oxidation behavior of laser cladding MCrAlY coatings on austenitic stainless steel

Abstract: The development of coatings has become technologically significant in many industries. A common approach in high temperature applications is the production of new thermal barrier coatings (TBCs). Laser cladding (LC) can be an alternative method to thermal spraying in the production of high quality bond coats in TBCs. In this work, dense coatings that formed adequate metallurgical bonds with the substrate were obtained by overlapping coaxial laser cladding. The oxidation behavior of the coating specimens was assessed by air furnace oxidation tests at 1100 °C for up to 200 h. The coatings' microstructures are composed of a γ matrix phase and a β interdendritic phase, confirmed by X-ray diffraction (XRD). At high temperatures, the growth and formation of oxide layers protect the underlying coating and substrate from oxidation at elevated temperatures. The possible formation and morphology of oxides on the oxidized surface were evaluated using scanning electron microscopy (SEM), XRD and atom force microscopy (AFM). The evaluation of the thickness and phases present in thermally grown oxide scales was evaluated using field emission scanning electron microscopy (FESEM) and energy dispersive spectroscopy microanalysis (EDS), with a previous cut using the Focused Ion Beam Ga Column (FIB) method.

Miniaturized Supercapacitors: Focused Ion Beam Reduced Graphene Oxide Supercapacitors with Enhanced Performance Metrics

Abstract: Miniaturization of energy storage devices with enhanced performance metrics can reduce the footprint of microdevices being used in our daily life. Micro-­supercapacitor architectures with planar geometry provides several advantages, such as, the ability to control and reduce the distances ions travel between two electrodes, easy integration to microdevices, and offer the potential of being extended into 3D without compromising the interelectrode distances. Here, focused ion beam (FIB) technology is used to directly write miniaturized planar electrode systems of reduced graphene oxide (FIB-rGO) on films of graphene oxide. Using optimized ion beam irradiation, interdigitated FIB-rGO electrode designs with 40 μm long and 3.5 μm wide fingers with ultrasmall interelectrode spacing of 1 μm demonstrate a large capacitance (102 mF cm−2), ultrasmall time response (0.03 ms), low equivalent series resistance (0.35 mΩ cm2), and retain 95% of the capacitance after 1000 cycles at an ultrahigh current density of 45 mA cm−2. These performance metrics show remarkable improvements on several counts of supercapacitor performance over existing reports due to the miniaturized electrode dimensions and minimal damage to the graphene sheets. It is believed that these results can provide avenues for large-scale fabrication of arrayed, planar, high-performance micro-supercapacitors with a small environmental footprint.

Erosion Mechanism of MoS2-Based Films Exposed to Atomic Oxygen Environments

Abstract: The erosion mechanism of magnetron sputtered MoS2 films exposed to the atomic oxygen environment was studied and compared with the Ti-doped MoS2 and MoS2/Ti multilayer films. The compositional and structural changes were investigated as a function of incident fluence by Rutherford back scattering (RBS) and focused ion beam combining with scanning electron microscopy (FIB&SEM). The RBS results indicate that the sulfur atoms are eroded by the incident atomic oxygen atoms and the removed sulfur amount increases but the erosion rate decreases with increasing of incident fluence. For pure MoS2 films the erosion process turns to saturate at the end of investigated fluence of 4.8 × 1021 O cm–2, and for Ti-doped and MoS2/Ti multilayer films the saturation of sulfur erosion is much earlier around incident fluence of 5.2 × 1019 and 2.6 × 1019 O cm–2, respectively. FIB cross-section results reveal that pores structures present in the as-deposited MoS2 films provide a reaction highway, which allows the incident atomi...

Integration of individual TiO2 nanotube on the chip: Nanodevice for hydrogen sensing

Abstract: Titania (TiO2) exists in several phases possessing different physical properties. In view of this fact, we report on three types of hydrogen sensors based on individual TiO2 nanotubes (NTs) with three different structures consisting of amorphous, anatase or anatase/rutile mixed phases. Different phases of the NTs were produced by controlling the temperature of post-anodization thermal treatment. Integration of individual TiO2 nanotubes on the chip was performed by employing metal deposition function in the focused ion beam (FIB/SEM) instrument. Gas response was studied for devices made from an as-grown individual nanotube with an amorphous structure, as well as from thermally annealed individual nanotubes exhibiting anatase crystalline phase or anatase/rutile heterogeneous structure. Based on electrical measurements using two Pt complex contacts deposited on a single TiO2 nanotube, we show that an individual NT with an anatase/rutile crystal structure annealed at 650 degrees C has a higher gas response to hydrogen at room temperature than samples annealed at 450 degrees C and as-grown. The obtained results demonstrate that the structural properties of the TiO2 NTs make them a viable new gas sensing nanomaterial at room temperature. (C) 2015 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim

Focused-ion beam patterning of organolead trihalide perovskite for subwavelength grating nanophotonic applications

Abstract: The coherent amplified spontaneous emission and high photoluminescence quantum efficiency of organolead trihalide perovskite have led to research interest in this material for use in photonic devices. In this paper, the authors present a focused-ion beam patterning strategy for methylammonium lead tribromide (MAPbBr3) perovskite crystal for subwavelength grating nanophotonic applications. The essential parameters for milling, such as the number of scan passes, dwell time, ion dose, ion current, ion incident angle, and gas-assisted etching, were experimentally evaluated to determine the sputtering yield of the perovskite. Based on our patterning conditions, the authors observed that the sputtering yield ranged from 0.0302 to 0.0719 μm3/pC for the MAPbBr3 perovskite crystal. Using XeF2 for the focused-ion beam gas-assisted etching, the authors determined that the etching rate was reduced to between 0.40 and 0.97, depending on the ion dose, compared with milling with ions only. Using the optimized patterning...

Optical fiber tip templating using direct focused ion beam milling

Abstract: We report on a method for integrating sub-wavelength resonant structures on top of optical fiber tip. Our fabrication technique is based on direct milling of the glass on the fiber facet by means of focused ion beam. The patterned fiber tip acts as a structured template for successive depositions of any responsive or functional overlay. The proposed method is validated by depositing on the patterned fiber a high refractive index material layer, to obtain a 'double-layer' photonic crystal slab supporting guided resonances, appearing as peaks in the reflection spectrum. Morphological and optical characterizations are performed to investigate the effects of the fabrication process. Our results show how undesired effects, intrinsic to the fabrication procedure should be taken into account in order to guarantee a successful development of the device. Moreover, to demonstrate the flexibility of our approach and the possibility to engineering the resonances, a thin layer of gold is also deposited on the fiber tip, giving rise to a hybrid photonic-plasmonic structure with a complementary spectral response and different optical field distribution at the resonant wavelengths. Overall, this work represents a significant step forward the consolidation of Lab-on-Fiber Technology.

Crystalline nano-coatings of fluorine-substituted hydroxyapatite produced by magnetron sputtering with high plasma confinement

Abstract: A radio-frequency magnetron sputtering technique operating in right-angle geometry (RAMS) with high plasma confinement was revised to produce thin films (15–570 nm) of fluorine-substituted hydroxyapatite, FHA, adapted to be used as nano-coatings for biomedical implants. An electron temperature of T eff ≈ 9.0 eV and a plasma electron density of 1.2 × 10 15 m − 3 assured the nucleation of an amorphous fluorine-substituted hydroxyapatite phase on Si and Ti surfaces. With the aid of a Langmuir probe, the RAMS plasma energy was tuned to control the coating stoichiometry and the ratio between the crystalline and amorphous phases. The energy delivered over time from the bombardment of ions and electrons transformed the amorphous calcium phosphate phase into crystalline fluorine-substituted hydroxyapatite. The crystalline films were obtained at room temperature. The partial substitution of OH − for F − in the HA structure was confirmed by X-ray diffraction using synchrotron radiation in grazing-incidence mode, X-ray photoelectron spectroscopy and attenuated total reflection Fourier transform infrared spectroscopy. High-resolution transmission electron microscopy carried out on cross-section film samples prepared by a focused ion beam (FIB) technique revealed that the film ultrastructure was composed of columnar crystals oriented perpendicularly to the substrate surface. The crystals were connected to the substrate surface by ordered nanolayers, indicating the existence of a continuous binding between the two materials. This work demonstrates that the RAMS technique is able to produce FHA nano-coatings with controlled chemical compositions and structures on metallic implants for clinical applications.

A state-of-the-art review of micron-scale spatially resolved residual stress analysis by FIB-DIC ring-core milling and other techniques

Abstract: Quantification of residual stress gradients can provide great improvements in understanding the complex interactions between microstructure, mechanical state, mode(s) of failure and structural integrity. Highly focused local probe non-destructive techniques such as X-ray diffraction, electron diffraction or Raman spectroscopy have an established track record in determining spatial variations in the relative changes in residual stress with respect to a reference state for many structural materials. However, the interpretation of these measurements in terms of absolute stress values requires a strain-free sample often difficult to obtain due to the influence of chemistry, microstructure or processing route. With the increasing availability of focused ion beam instruments, a new approach has been developed which is known as the micro-scale ring-core focused ion beam-digital image correlation technique. This technique is becoming the principal tool for quantifying absolute in-plane residual stresses. It can b...