Magneto-ionics relies on the voltage-driven transport of ions to modify magnetic properties. As a diffusion-controlled mechanism, defects play a central role in determining ion motion and, hence, magneto-ionic response. Here, the potential of ion implantation is exploited to engineer depth-resolved defect type and density with the aim to control the magneto-ionic behavior of Co3O4 thin films. It is demonstrated that through a single implantation process of light ions (He+) at 5 keV, the magneto-ionic response of a nanostructured 50 nm thick Co3O4 film, in terms of rate and amount of induced magnetization, at short-, mid-, and long-term voltage actuation, can be controlled by varying the generated collisional damage through the ion fluence. These results constitute a proof-of-principle that paves the way to further use ion implantation (tuning the ion nature, energy, fluence, target temperature, or using multiple implantations) to enhance performance in magneto-ionic systems, with implications in ionic-based devices. Light-ion implantation is exploited to engineer depth-resolved defect type and density along nanostructured 50 nm thick Co3O4 films. This allows for the control of the magneto-ionic response of the Co3O4 thin films in terms of rate and amount of induced magnetization, at short-, mid-, and long-term voltage actuation, by varying the generated collisional damage through ion fluence. image

We tested the feasibility of a novel machined silicon nanopore enrichment device to recover individual microbial taxa from anaerobic sediments. Unlike other environmental isolation devices that have multiple entry points for bacteria or require the sample to be manually placed inside of a culturing chamber, our silicon device contains 24 precisely sized and spaced nanopores, each of which is connected to one culturing well, thereby providing only one entry point for bacteria. The culturing wells allow nutrient transport, so the bacteria that enter continue to experience their natural chemical environment, allowing collection of microbes without manipulating the environment. The device was deployed in marsh sediment and subsequently returned to the laboratory for bacterial culturing and analysis. 16S rRNA marker gene and metagenomic sequencing was used to quantify the number of different microbial taxa cultured from the device. The 16S rRNA sequencing results indicate that each well of the device contained between 1 and 62 different organisms from several taxonomic groups, including likely novel taxa. We also sequenced the metagenome from 8 of the 24 wells, enabling the reconstruction of 56 metagenomic assembled genomes (MAGs), and 44 of these MAGs represented non-redundant genome reconstructions. These results demonstrate that our novel silicon nanofluidic device can be used for isolating and culturing consortia containing a small number of microbial taxa from anaerobic sediments, which can be very valuable in determining their physiological potential. Importance There are very few methods that can remove a few bacterial cells from a complex environment and keep the cells alive so that they can propagate sufficiently to be analyzed in a laboratory. Such methods are important to develop because the physiological functions of individual species of bacteria are often unknown, cannot be determined directly in the complex sample, and many bacterial cells cannot be grown outside of their natural environment. A novel bacterial isolation device has been made tested in a salt marsh. The results show that the device successfully isolated small groups of bacterial species from the incredibly diverse surroundings. The communities of bacteria were easily removed from the device in the laboratory and analyzed.

Magneto-ionics, which deals with the change of magnetic properties through voltage-driven ion migration, is expected to be one of the emerging technologies to develop energy-efficient spintronics. While a precise modulation of magnetism is achieved when voltage is applied, much more uncontrolled is the spontaneous evolution of magneto-ionic systems upon removing the electric stimuli (i.e., post-stimulated behavior). Here, we demonstrate a voltage-controllable N ion accumulation effect at the outer surface of CoN films adjacent to a liquid electrolyte, which allows for the control of magneto-ionic properties both during and after voltage pulse actuation (i.e., stimulated and post-stimulated behavior, respectively). This effect, which takes place when the CoN film thickness is below 50 nm and the voltage pulse frequency is at least 100 Hz, is based on the trade-off between generation (voltage ON) and partial depletion (voltage OFF) of ferromagnetism in CoN by magneto-ionics. This novel effect may open opportunities for new neuromorphic computing functions, such as post-stimulated neural learning under deep sleep.

Magneto-ionics is an emerging actuation mechanism to control the magnetic properties of materials via voltage-driven ion motion. This effect largely relies on the strength and penetration of the induced electric field into the target material, the amount of generated ion transport pathways, and the ionic mobility inside the magnetic media. Optimizing all these factors in a simple way is a huge challenge, although highly desirable for technological applications. Here, we demonstrate that the introduction of suitable transition-metal elements to binary nitride compounds can drastically boost magneto-ionics. More specifically, we show that the attained magneto-ionic effects in CoN films (i.e., saturation magnetization, toggling speeds, and cyclability) can be drastically enhanced through 10% substitution of Co by Mn in the thin-film composition. Incorporation of Mn leads to transformation from nanocrystalline into amorphous-like structures, as well as from metallic to semiconducting behaviors, resulting in an increase of N-ion transport channels. Ab initio calculations reveal a lower energy barrier for CoMn-N compared to Co-N that provides a fundamental understanding of the crucial role of Mn addition in the voltage-driven magnetic effects. These results constitute an important step forward toward enhanced voltage control of magnetism via electric field-driven ion motion.

Electric-field-driven ion motion to tailor magnetic properties of materials (magneto-ionics) offers much promise in the pursuit of voltage-controlled magnetism for highly energy-efficient spintronic devices. Electrolyte gating is a relevant means to create intense electric fields at the interface between magneto-ionic materials and electrolytes through the so-called electric double layer (EDL). Here, improved magneto-ionic performance is achieved in electrolyte-gated cobalt oxide thin films with the addition of inorganic salts (potassium iodide, potassium chloride, and calcium tetrafluoroborate) to anhydrous propylene carbonate (PC) electrolyte. Ab initio molecular dynamics simulations of the EDL structure show that K+ is preferentially located on the cobalt oxide surface and KI (when compared to KCl) favors the accumulation of positive charge close to the surface. It is demonstrated that room temperature magneto-ionics in cobalt oxide thin films is dramatically enhanced in KI-containing PC electrolyte at an optimum concentration, leading to 11-fold increase of generated magnetization and 35-fold increase of magneto-ionic rate compared to bare PC.

Voltage control of magnetism via electric-field-driven ion migration (magneto-ionics) has generated intense interest due to its potential to greatly reduce heat dissipation in a wide range of information technology devices, such as magnetic memories, spintronic systems or artificial neural networks. Among other effects, oxygen ion migration in transition-metal-oxide thin films can lead to the generation or full suppression of controlled amounts of ferromagnetism ('ON-OFF' magnetic transitions) in a non-volatile and fully reversible manner. However, oxygen magneto-ionic rates at room temperature are generally considered too slow for industrial applications. Here, we demonstrate that sub-second ON-OFF transitions in electrolyte-gated paramagnetic cobalt oxide films can be achieved by drastically reducing the film thickness from >200 nm down to 5 nm. Remarkably, cumulative magneto-ionic effects can be generated by applying voltage pulses at frequencies as high as 100 Hz. Neuromorphic-like dynamic effects occur at these frequencies, including potentiation (cumulative magnetization increase), depression (i.e., partial recovery of magnetization with time), threshold activation, and spike time-dependent magnetic plasticity (learning and forgetting capabilities), mimicking many of the biological synapse functions. The systems under investigation show features that could be useful for the design of artificial neural networks whose magnetic properties would be governed with voltage.

Omnidirectional absorption is important to non-tracking systems designed for the harvesting of solar energy. Presently, we examine both experimentally and numerically the broadband absorption under oblique illumination driven by deep sidewall subwavelength structures (DSSS) in silicon nanopillar arrays (DSSS arrays). Specifically, we target DSSS geometries that are a built-in side effect of the top-down cyclic Bosch dry etch process employed to realize high aspect ratio silicon nanopillar (NP) arrays. We numerically compare the DSSS array with an optically-optimized straight-sidewall nanopillar array (SSNP array) under oblique illumination. We show how the presence of DSSS generates a higher absorptivity particularly for the spectral range >600 nm, induces the formation of absorptivity peaks at the near-infrared spectral range, and overall provides an enhanced omnidirectional broadband absorption. We experimentally show that the specular reflectivity and the total reflectivity of silicon DSSS arrays that were fabricated using a top-down Bosch dry etch process is significantly lower compared with that of the corresponding SSNP arrays. Specifically, we show a decrement in the broadband specular reflection of up to 30% for certain angles of illumination, and about 13% decrement in the total reflectivity.

This work presents a flexible polyimide-based capacitive tactile sensing array with sub-millimeter spatial resolution. The sensor is conceived to be embedded in a multimodal artificial finger to detect and classify the texture morphology of an object's surface. The proposed tactile sensor comprises a 16 x 16 array of capacitive sensing units. Each unit is composed of a parallel square electrode pairs (340 mu m x 340 mu m) separated by a compressible air cavity and embedded into a flexible polyimide substrate. Standard MEMS microfabrication techniques were used to develop the sensor. The polyimide device was covered with a thin compressible PDMS layer to tune the normal pressure sensitivity and dynamic range (225-430 mu m thin PDMS layer resulting in 0.23-0.14 fF/kPa). The detection of the surface morphologies of a regular grating stamp for different orientation and a small metallic nut placed on the sensor is demonstrated, showing a 420 mu m spatial resolution. The proposed sensor represents a novel capacitive tactile sensing device with a sub-mm resolution of human fingertip sensitivity.

Light trapping and the broadband absorption of the solar radiation are significant to a plethora of absorption-based photonic devices. Specifically, efficient broadband absorption was recently demonstrated with arrays of subwavelength structures. The current study examines both numerically and experimentally light trapping driven by deep sidewall subwavelength structures (DSSS) in silicon nanopillar (NP) arrays (DSSS arrays). Particularly, the focus is on DSSS geometries that are an inherent outcome of the top-down dry etch approach used in arrays of high aspect ratio NPs due to the periodical operationality of the Bosch dry etch method. ~10% enhancement in the broadband absorption of DSSS arrays compared with NP arrays is demonstrated numerically, as well as the generation of near-IR absorptivity peaks of ~25% for DSSS arrays. Importantly, it is shown that the introduction of DSSS systematically blue-shifts the absorptivity peaks of the NP arrays and in this manner a deterministic light trapping is possible. Finally, decrements of ~40% in direct reflectivity and ~7% in diffused reflectivity in DSSS arrays realized on silicon wafers is demonstrated experimentally.

Large-area and dense arrays of nanometric scale structures are commonly fabricated for several applications. The characterisation of sub-micron structures (below 1 mu m) at a large scale as well as the related data analysis are challenging tasks. Here, we present a method to address the image acquisition, the data extraction and the data analysis, applied to the evaluation of the uniformity of nanometric structures in a silicon master. Automated routines for both high and low magnification Scanning Electron Microscope (SEM) imaging have been successfully developed. SEM images have been automatically acquired by scripting routines, which collect large amounts of images of the nanometric structures covering multiple regions of the wafer in a few hours. Geometric parameters of the nanometric structures such as diameter, period and height have been extracted from the raw images using the developed image processing scripts. Finally, the data extracted from more than 4800 images acquired with three different characterisation scripts (1600 images for each study) have been analysed and plotted according to their position in the wafer.

Electromigration (EM) is an important phenomenon in microelectronics, widely studied and modeled in chip design in the last decades. More recently, the increase of packaging density pushed EM studies outside of the chip. In Wafer Level Fan-In and Wafer Level Fan-Out designs, EM studies have focused on the package solder joins, due to the poor robustness of solder alloys to EM. Inside the package, the copper traces in the redistribution layer (RDL) have not been considered critical because the minimum cross-sectional area of RDL technology had non-critical current densities. However, the constant demand for packaging miniaturization is requiring even higher RDL densities, with line/space (L/S) <;5 μm under development for fan-out and L/S<;2 μm for fan-in. Due to RDL process limitations, L/S reduction carries a quadratic reduction on the trace's cross-section, which can have a significant impact on EM reliability. Moreover, while IC lines are embedded in a thermally-conductive medium, RDL lines are built on dielectrics with poor heat dissipation and, also critical, fan-out packages have areas / materials with very different thermal conductivity - silicon (Si), mold compound (MC), which lead to hotter and uneven line temperatures and consequently different EM rates. This paper studies the EM effects in RDL and quantifies its impact on reliability and product life expectancy for Amkor's WLFI/WLFO technologies. The increase of relative resistance, ΔR/R, was analyzed on highly stressed RDL Cu traces, built over Si and MC units to test the extreme conditions in fan-out packages. Both continuous and on-off cycled temperature tests were conducted to investigate the thermomechanical stress impact on EM. The results showed very different increase rates of ΔR/R due to the very different thermal dissipation abilities, identigying the need for specific RDL design rules. In the continuous temperature tests, the fairly linear increase of ΔR/R suggested the use of a degradation rate (DR) to characterize the EM effects in a very fast way, instead of determining mean time to failure (MTTF) figures that are time-consuming and depend on arbitrary and heuristic failure criteria (e.g., 20% rise of ΔR/R). The linear extrapolation enabled by the DR also allowed the fast build-up of MTTF Weibull plots that would otherwise take several months to complete. A model for the DR, adapted from Black's model, was developed for the statistical estimation of mean DR for a given temperature and current density. In the on-off cycled temperature test, a stepwise behavior of ΔR/R was observed, with general reduction of net MTTF, while DR acceleration was only observed on the MC units, pointing to external thermomechanical-induced effects on the measured ΔR/R, which are filtered by the DR analysis.