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The focused ion beam (FIB) is a powerful tool for the 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 the various research communities, we aim to identify future pathways for ion source and instrumentation development as well as emerging applications, and the scope 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 interests 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., Comment: This publication is based upon work from the COST Action FIT4NANO CA19140, supported by COST (European Cooperation in Science and Technology) https://www.cost.eu/. Financial support from COST Action CA19140 is acknowledged http://www.fit4nano.eu/ Version 3 has many text and language edits as well as layout tuning but no substantial new content

Chiral lattice modes are hybrid states arising from chiral plasmonic particles assembled in ordered arrays with opportune periodicity. These resonances exhibit dependence on excitation handedness, and their observation in plasmonic lattices is strictly related to the chiroptical features of the fundamental plasmonic unit. Here, we show the emergence of chiral surface lattice resonances in properly engineered arrays of nanohelices, fully 3D chiral nano-objects fabricated by focused ion beam processing. By tuning the relative weight of plasmonic and photonic components in the hybrid mode, we analyze the physical mechanism of strong diffractive coupling leading to the emergence of the lattice modes, opening the way to the engineering of chiral plasmonic systems for sensing applications. In particular, we identify a coupling regime where the combination of a large intrinsic circular dichroism of the plasmonic resonance with a well-defined balance between the photonic quality factor and the plasmonic field enhancement maximizes the capability of the system to discriminate refractive index changes in the surrounding medium. Our results lay the foundation for exploiting circular dichroism in plasmonic lattices for high performance biosensing., Comment: 9 pages, 4 figures + supporting

Fine control of the chiral light-matter interaction at the nanoscale, by exploiting designed metamaterial architecture, represents a cutting-edge craft in the field of biosensing, quantum and classic nanophotonics. Recently, artificially engineered 3D nanohelices have demonstrated programmable wide chiroptical properties by tuning materials and architecture, but fundamental diffractive aspects that are to the origin of chiral resonances still remain elusive. Here, we proposed a novel concept of three-dimensional chiral MetaCrystal, where the chiroptical properties are finely tuned by in-plane and out-of-plane diffractive coupling. Different chiral dipolar modes can be excited along the helix arms, generating far field optical resonances and radiation pattern with in-plane side lobes and suggesting that a combination of efficient dipole excitation and diffractive coupling matching controls the collective oscillations among the neighbor helices in the chiral MetaCrystal. This concept enables the tailorability of chiral properties in a broad spectral range for a plethora of forefront applications, since the proposed compact chiral MetaCrystal can be suitable for integration with quantum emitters and can open perspectives in novel schemes of enantiomeric detection., Comment: 22 pages (article + supporting information) 5 figures

Highly sensitive and selective label free devices for real-time identification of specific biomarkers are expected to significantly impact the biosensing field. The ability of plasmonic systems to confine the light in nanometer volume and to manipulate it by tuning the size, shape and material features of the nanostructures, makes these systems promising candidates for biomedical devices. In this work we demonstrate the engineered sensing capabilities of a compact array of 3D metal dielectric core-shell chiral metamaterial. The intrinsic chirality of the nano-helices makes the system circular polarization dependent and unaffected by the background interferences, allowing to work even in complex environment. The core-shell architecture enhances the sensing properties of the chiral metamaterial on both in the far and near field, offering also a large surface to molecular immobilization. With our system we recorded sensitivity of about 800nm/RIU and FOM= 1276 RIU-1. The sensing abilities of the system is demonstrated with the detection of the of the TAR DNA-binding protein 43 (TDP-43) , a critical biomarker for the screening of neurodegenerative diseases. In particular, the sensor was tested in different environments, such as human serum, with concentrations ranging from 1pM down to 10fM, opening new perspectives for novel diagnostic tools., Comment: 13 pages 6 figures plus supporting

In recent years significant efforts have been made to design and fabricate functional nanomaterials for biomedical applications based on the control of light matter interaction at the nanometer scale. Among many other artificial materials, hyperbolic dispersion metamaterials allow to access unprecedented physical effects and mechanisms due to the extreme anisotropy of their optical constants. The unbound isofrequency surface of hyperbolic metamaterials (HMMs) enable the possibility to support a virtually infinite density of states and ultra-high confinement of electromagnetic fields, allowing perfect absorption of light and extreme sensing properties. Optical sensor technology based on plasmonic metamaterials offers significant opportunities in the field of clinical diagnostics, particularly for the detection of low-molecular-weight biomolecules in highly diluted solutions. In this context, we present a computational effort to engineer a biosensing platform based on hyperbolic metamaterials, supporting highly confined bulk plasmon modes integrated with out-of-plane chiral metasurfaces. The role of the helicoidal chiral metasurface is manifold: i) as a diffractive element to increase the momentum of the incoming light to excite the plasmon sensing modes with linearly and circularly polarized light; ii) as out-of-plane extended sensing surface to capture target analytes away from the substrate thereby the diffusion limit; iii) as a plamonic chiral nanostructure with enhanced sensing performance over circularly polarized reflectance light.