Focused ion beam (FIB) technology has transformed materials science by enabling precise micro- and nano-scale modifications through ion beam interactions. Originally developed for semiconductor doping and device fabrication, FIBs use different ionization sources such as liquid metals (e.g., gallium), gas field ionization, and plasma sources. Recent advancements include the use of Ionic Liquid Ion Sources (ILIS), which promise enhanced capabilities for materials research and applications. Recent progress in the Ionic Liquid Ion Sources- Focused ion beam (ILIS-FIB) technology is presented in this overview paper. ILIS-FIB systems operate similarly to conventional systems but employ ionic liquids (ILs) as ion sources, ionizing IL molecules at the emitter tip with applied voltage and using standard focusing components to refine the ion beam. Challenges which are reviewed in this article, include maintaining pure ionic emission for stable operation, necessitating optimization of tip emitting properties, IL characteristics, and voltage settings. It was reviewed in this paper that, ILIS-FIB systems use room-temperature ILs with low melting points, low vapor pressures, and customizable chemical compositions to ensure pure ion emission and improve beam performance for emerging applications. Despite challenges in beam composition and commercial readiness, ILIS-FIB research focuses on developing mathematical models to predict beam stability and performance, advancing theoretical groundwork for refinement and eventual commercialization of ILIS-based FIB technologies in materials science. This overview can shed light on the understanding of ionic liquid ion sources for Focused Ion Beam applications.

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.

We report on the development of an ion beam irradiation facility for focusing beams of highly charged ions (HCI) down to diameters in the low micrometer range. The use of highly charged noble gas ions creates unique features leading to applications and technical solutions which can complement the existing equipment market. The developed, built and commissioned facility consists of an electron beam ion source (EBIS), a downstream Wien filter for ion mass and charge state separation, an ion-optical column for the fine-focussed ion beam (FIB) formation, a target chamber with a sample transfer system, a sample holder with sub-micrometer positioning precision and a ToF-SIMS spectrometer for high-resolved surface analysis.

30 keV Ga + irradiation-induced changes of magnetic and magneto-optical properties of sputtered Pt/Co/Pt ultrathin trilayers films have been studied as a function of the ion fluence. Out-of-plane magnetic anisotropy states with enhanced magneto-optical effects were evidenced for specific values of cobalt thickness and irradiation fluence. Results obtained after uniform or quasi-uniform focused ion beam irradiation on either out-of-plane or in-plane magnetized sputtered pristine trilayers are compared. Similar irradiation-induced magnetic changes are evidenced in quasi-uniformly focused ion beam or uniformly irradiated films, grown either by sputtering or molecular beam epitaxy. We discuss on plausible common mechanisms underlying the observed effects.

In this article, the authors review, compare, and discuss the characteristics and applicative potential of a variety of nongallium ion liquid metal ion sources they have developed and successfully applied to nanopatterning. These sources allow generating on-demand ion beams and are promising for extending focused ion beams applications. They detail the operating characteristics of such sources capable to emit metal projectiles ranging from atomic ions with different charge states to polyatomic ions and to large metal clusters having sizes up to a few nanometers. They highlight their interest and relevance to current nanoscience challenges in terms of ultimate patterning or bottom-up nanofabrication capabilities.

Zero-mode waveguides (ZMWs) are optical nanostructures fabricated in a thin metallic film capable of confining the excitation volume to the zeptoliter range. In this work we describe the batch fabrication of a nanopore-based device, based upon high-resolution arrays of nanopores (of various sizes), which is used to directly measure the passage of DNA. In our method, nanopores are fabricated in ultrathin dielectric films with a deposited gold layer. The gold layer on the device induces a zero mode waveguide illumination at the cis end of the nanopores. The method presented allows for optical detection, in real time, at the level of a single molecule and a single pore. The detection of fluorescently labelled single molecules passing through the pores, measured using an electron multiplying charge coupled device camera, is described. Molecules inside the nanopore were invisible until they reached the volume illuminated by the evanescent field. This fabrication methodology appears to be very promising for the development and batch fabrication of a new generation of nanopore-based sensor devices. (C) 2017 Elsevier B.V. All rights reserved.

Nano device prototyping (NDP) is essential for realizing and assessing ideas as well as theories in the form of nano devices, before they can be made available in or as commercial products. In this review, application results patterned similarly to those in the semiconductor industry (for cell phone, computer processors, or memory) will be presented. For NDP, some requirements are different: thus, other technologies are employed. Currently, in NDP, for many applications direct write Gaussian vector scan electron beam lithography (EBL) is used to define the required features in organic resists on this scale. We will take a look at many application results carried out by EBL, self-organized 3D epitaxy, atomic probe microscopy (scanning tunneling microscope/atomic force microscope), and in more detail ion beam techniques. For ion beam techniques, there is a special focus on those based upon liquid metal (alloy) ion sources, as recent developments have significantly increased their applicability for NDP.

Today, Focused Ion Beam (FIB) processing is nearly exclusively based on gallium Liquid Metal Ion Sources (LMIS). But, many applications in the mu m- or nm range could benefit from ion species other than gallium: local ion implantation, ion beam mixing, ion beam synthesis, or Focused Ion Beam Lithography (IBL). Therefore, Liquid Metal Alloy Ion Sources (LMAIS) represent a promising alternative to expand the remarkable application fields for FIB. Especially, the IBL process shows potential advantages over, e.g., electron beam or other lithography techniques: direct, resistless, and three-dimensional patterning, enabling a simultaneous in-situ process control by cross-sectioning and inspection. Taking additionally into account that the used ion species influences significantly the physical and chemical nature of the resulting nanostructures-in particular, the electrical, optical, magnetic, and mechanic properties leading to a large potential application area which can be tuned by choosing a well suited LMAIS. Nearly half of the elements of the periodic table are recently available in the FIB technology as a result of continuous research in this area during the last forty years. Key features of a LMAIS are long life-time, high brightness, and stable ion current. Recent developments could make these sources feasible for nano patterning issues as an alternative technology more in research than in industry. The authors will review existing LMAIS, LMIS other than Ga, and binary and ternary alloys. These physical properties as well as the fabrication technology and prospective domains for modern FIB applications will similarly be reviewed. Other emerging ion sources will be also presented and their performances discussed. Published by AIP Publishing.

Laser sources with a controllable flexible wavelength have found widespread applications in optical fiber communication, optical sensing, and microscopy. Here, we report a tunable mode-locked fiber laser using a graphene-based saturable absorber and a tapered mirror as an end mirror in the cavity. The phase layer in the mirror is precisely etched by focused ion beam (FIB) milling technology, and the resonant wavelength of the mirror shifts correspond to the different etch depths. By scanning the tapered mirror mechanically, the center wavelength of a mode-locked fiber laser can be continuously tuned from 1562 to 1532 nm, with a pulse width in the sub-ps level and repetition rate of 27 MHz.

Fabrication of nanopores and nanomasks has recently emerged as an area of considerable interest for research applications ranging from optics, to electronics and to biophysics. In this work we evaluate and compare the fabrication of nanopores, using a finely focused gallium beam, in free-standing membranes/films made of Si, SiN, and SiO"2 (having thicknesses of a few tens of nanometers) and also in graphene and hexagonal boron nitride (h-BN) atomically thin suspended sheets. Mechanical resistance, charging effects and patterning performances are evaluated and compared. In spite of the very different properties of the membranes we report that reproducible nanopore fabrication in the sub-10nm range can be achieved in both amorphous and atomically thin sheets using Ga^+ focused ion beams (FIB).

Focused ion beam milling has been applied to fabricate an ultra-thin taper structure on crystalline indium phosphide to realize a multi-wavelength vertical cavity photonic device. The appropriate FIB scanning procedures and operating parameters were used to control the target material re-deposition and to minimize the surface roughness of the milled area. The sputtering yield of crystalline indium phosphide target was determined by investigating the relationship between milling depth and ion dose. By applying the optimal experimentally obtained yield and related dose range, we have fabricated an ultra-thin taper structure whose etch depths are precisely and progressively tapered from 25 nm to 55 nm, with a horizontal slope of about 1:13,000. The optical characterization of this tapered device confirms the expected multi-wavelength behavior of our device and shows that the optical losses induced by the FIB milling process are negligible. (C) 2014 Elsevier B.V. All rights reserved.

In this article we review some fundamentals of the Focused Ion Beam (FIB) technique based on scanning finely focused beams of gallium ions over a sample to perform direct writing. We analyse the main limitations of this technique in terms of damage generation or local contamination and through selected examples we discuss the potential of this technique in the light of the most sensitive analysis techniques. In particular we analyse the limits of Ga-FIB irradiation for the patterning of III-V heterostructures, thin magnetic layers, artificial defects fabricated onto graphite or graphene and atomically thin suspended membranes. We show that many of these early-pointed "limitations" with appropriate attention and analysis can be valuable for FIB instrument development, avoided, or even turned into decisive advantages. Such new methods transferable to the fabrication of devices or surface functionalities are urgently required in the emerging nanosciences applications and markets.

We report on the fabrication of fully suspended two-dimensional electron and hole gases in III-V heterostructures. Low temperature transport measurements verify that the properties of the suspended gases are only slightly degraded with respect to the non-suspended gases. Focused ion beam technology is used to pattern suspended nanostructures with minimum damage from the ion beam, due to the small width of the suspended membrane.

We report on the selective creation of spin filtering regions in non-magnetic InGaAs layers by implantation of Ga ions by Focused Ion Beam. We demonstrate by photoluminescence spectroscopy that spin dependent recombination (SDR) ratios as high as 240% can be achieved in the implanted areas. The optimum implantation conditions for the most efficient SDR are determined by the systematic analysis of different ion doses spanning four orders of magnitude. The application of a weak external magnetic field leads to a sizable enhancement of the SDR ratio from the spin polarization of the nuclei surrounding the polarized implanted paramagnetic defects.

Instabilities and strong spatiotemporal fluctuations in out-of-plane demagnetized stripe domain patterns of a Pt/Co(0.5 nm)/Pt film designed by Ga${}^{+}$ ion irradiation were visualized by polar magneto-optical Kerr effect microscopy and studied in the spin reorientation transition temperature region. A two-dimensional-stripe melting transition was evidenced before reaching the in-plane spin state. Slow dynamics were driven by short-range instabilities on magnetic defects which trigger long-range transverse wall fluctuations. The spatial and temporal behavior of stripelike ``floating'' patches was investigated. Dynamics cannot be simply interpreted by models previously proposed for liquid crystals.

In this article we report on carving nanopores into suspended graphene sheets using a finely focused and shaped gallium ion beam. We show that in addition to serving as a nearly ideal substrate for high resolution patterning, suspended graphene can be patterned with high accuracy using a methodology that is described. Furthermore, shapes and dimensions of the fabricated nanopores were investigated, showing stable structures that do not follow the circular shape of the FIB probe. These results highlight the role of preferential engraving directions during the carving process of the graphene material. We conclude in confirming the highly insulating properties of such graphene when immersed in an ionic solution, which is of particular interest for experiments such as DNA translocation.

In this paper, we report on the surface patterning of punctual defects onto graphene films grown on 6H-SiC(0001) substrates, using a finely focused gallium (Ga^+) ion beam. We present organized arrays of nano-defects, designed using ion doses in the range of 10-1x10^6Ga^+ ions/dot. Using Conductive Atomic Force Microscopy (CAFM) and Raman spectroscopy we evidence the strong resilience of graphene towards ion irradiation and characterize the morphology and the electronic properties of the FIB-induced local nano-defects. We show that punctual ion irradiation and dose control allow progressive amorphization of graphene leading to the promising perspective of graphene-based tunable templates.

We present here an overview on unfolding of biomolecular structures as DNA double strands or protein folds. After some theoretical considerations giving orders of magnitude about transport timescales through pores, forces involved in unzipping processes … we present our experiments on DNA unzipping or protein unfolding using a nanopore. We point out the difficulties that can be encountered during these experiments, such as the signal analysis problems, noise issues, or experimental limitations of such system.