Recording infraslow brain signals (<0.1 Hz) with microelectrodes is severely hampered by current microelectrode materials, primarily due to limitations resulting from voltage drift and high electrode impedance. Hence, most recording systems include high-pass filters that solve saturation issues but come hand in hand with loss of physiological and pathological information. In this work, we use flexible epicortical and intracortical arrays of graphene solution-gated field-effect transistors (gSGFETs) to map cortical spreading depression in rats and demonstrate that gSGFETs are able to record, with high fidelity, infraslow signals together with signals in the typical local field potential bandwidth. The wide recording bandwidth results from the direct field-effect coupling of the active transistor, in contrast to standard passive electrodes, as well as from the electrochemical inertness of graphene. Taking advantage of such functionality, we envision broad applications of gSGFET technology for monitoring infraslow brain activity both in research and in the clinic.

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.

Owing to their low dark current, high transparency, high thermal conductivity and potential radiation hardness, there is a special interest in silicon carbide devices for radiation monitoring in radiation harsh environments and with elevated temperatures and, especially, for the plasma diagnostic systems in future nuclear fusion reactors. In this work, four-quadrant pn junction diodes produced on epitaxial 4H-SiC substrates are studied. The impact of electron, neutron and proton irradiations (up to fluences of 1x1016 e/cm2, 2x1015 n/cm2 and 2.5x1015 p/cm2, respectively) on the electrical characteristics is studied by means of current-voltage (I-V) and capacitance-voltage (C-V) techniques. Relevantly, regardless of particle type and applied fluences, the results show similar low reverse currents for irradiated SiC devices, which are at least about four orders of magnitude lower than comparable Si devices. The effects of irradiation on interquadrant resistance and charge build-up in the interquadrant isolation are assessed. Furthermore, device performance as a radiation detector is investigated upon exposure to a collimated 239Pu-241Am-244Cm tri-alpha source. The performance at room temperature is preserved even for the highest irradiation fluences, and despite the fact that the rectification character in electrical characteristics is lost. From the results, advantages of using SiC devices in alpha particle detection in harsh environments can be envisaged.

Using a graphite cap to cover the silicon carbide (SiC) sample, it is shown that large isolated graphene anisotropic ribbons can be grown on the C face of on-axis, semi-insulating, $6H$-SiC wafers. The role of the cap is to modify the physics of the surface reconstruction process during Si sublimation, making more efficient the reconstruction of few selected terraces with respect to the others. The net result is the formation of a strongly step-bunched morphology with, in between, long (up to $600\mu \text{m}$) and large (up to $5\mu \text{m}$) homogeneous monolayers of graphene ribbons. This is shown by optical and scanning electron microscopy, while a closer view is provided by atomic force microscopy (AFM). From Raman spectroscopy, it is shown that most of the ribbons are homogeneous monolayers or bilayers of graphene. It is also shown that most of the thermal stress between the graphene layer and the $6H$-SiC substrate is relaxed by wrinkles. The wrinkles can be easily displaced by an AFM tip, which demonstrates evidence of graphene ironing at the nanoscale. Finally and despite the very low optical absorption of a single graphene layer, one shows that differential optical microtransmission can be combined to the micro-Raman analysis to confirm the monolayer character of the thinnest ribbons.