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The development of spintronic devices has been limited by the poor compatibility between semiconductors and ferromagnetic sources of spin. The broken inversion symmetry of some semiconductors may allow for spin–charge interconversion, but its control by electric fields is volatile. This has led to interest in ferroelectric Rashba semiconductors, which combine semiconductivity, large spin–orbit coupling and non-volatility. Here we report room-temperature, non-volatile ferroelectric control of spin-to-charge conversion in epitaxial germanium telluride films. We show that ferroelectric switching by electrical gating is possible in germanium telluride, despite its high carrier density. We also show that spin-to-charge conversion has a similar magnitude to what is observed with platinum, but the charge current sign is controlled by the orientation of ferroelectric polarization. Comparison between theoretical and experimental data suggests that the inverse spin Hall effect plays a major role in switchable conversion. The ferroelectric polarization of epitaxial thin films of germanium telluride can be switched by electrical gating and used to control spin-to-charge conversion.

We report on the formation of gas bubbles during the release of MEMS devices using buffered oxide etch. Several approaches to mitigate the problem are proposed and tested together with a qualitative study of the phenomenon. The chemical reaction behind such phenomenon and the influence of defects and topography is discussed. Finally, a comparison with the HF-vapor release technique is shown.

Although metal/ferroelectric/semiconductor tunnel junctions have been attracting widespread interest as next-generation memory devices, only limited effort has been devoted so far to quantitatively address their current–voltage characteristics and their achievable memory window. In this article, we show experimental data on template Pt/BaTiO3/Nb:SrTiO3 tunnel junctions confirming, first of all, that large memory windows can be achieved in these devices when the switching of the electric polarization in the ferroelectric layer moves the substrate between an accumulation and a depletion condition. Besides, by measuring the current–voltage curve of the devices quickly after the set/reset pulses used for polarization switching, the importance of considering the detrimental effects of the large depolarization fields in the ferroelectric layer when assessing the device memory window is demonstrated. The experimental data are, then, reproduced by a model for electron transport through the junction accounting for both drift/diffusion and distributed tunneling in the semiconductor. The model allows to catch a comprehensive physical picture of device operation and represents a powerful tool for the design and optimization of ferroelectric tunnel junctions with semiconductor electrodes.

In this article we present silicon oxycarbide (SiOC) as a potential dielectric platform for integrated photonic applications. By controlling the amount of carbon and oxygen in the composition of SiOC films, which in this work are deposited by using a reactive RF magnetron sputtering process, the refractive index of the material can be widely tuned from less than that of silica 1.40 to almost that of silicon carbide (3.0), while keeping high transparency in the near-infrared wavelength range. An in-depth analysis of the structural, morphological and optical properties of the deposited SiOC thin films is reported, pointing out the relationship between the change in the film composition and the tuneability of the refractive index. Single mode optical waveguides with a refractive index contrast of up to 28% and propagation loss as low as 2 dB/cm at 1550 nm are demonstrated. An integrated Mach-Zehnder interferometer is presented as a first example of PIC realized on high refractive index SiOC platform. Results show that SiOC is a promising alternative to conventional dielectric platforms for the realization of PICs.

The expression “quantum materials” identifies materials whose properties “cannot be described in terms of semiclassical particles and low-level quantum mechanics”, i.e., where lattice, charge, spin and orbital degrees of freedom are strongly intertwined. Despite their intriguing and exotic properties, overall, they appear far away from the world of microsystems, i.e., micro-nano integrated devices, including electronic, optical, mechanical and biological components. With reference to ferroics, i.e., functional materials with ferromagnetic and/or ferroelectric order, possibly coupled to other degrees of freedom (such as lattice deformations and atomic distortions), here we address a fundamental question: “how can we bridge the gap between fundamental academic research focused on quantum materials and microsystems?”. Starting from the successful story of semiconductors, the aim of this paper is to design a roadmap towards the development of a novel technology platform for unconventional computing based on ferroic quantum materials. By describing the paradigmatic case of GeTe, the father compound of a new class of materials (ferroelectric Rashba semiconductors), we outline how an efficient integration among academic sectors and with industry, through a research pipeline going from microscopic modeling to device applications, can bring curiosity-driven discoveries to the level of CMOS compatible technology.

The search for new rapid diagnostic tests for malaria is a priority for developing an efficient strategy to fight this endemic disease, which affects more than 3 billion people worldwide. In this study, we characterize systematically an easy-to-operate lab-on-chip, designed for the magnetophoretic capture of malaria-infected red blood cells (RBCs). The method relies on the positive magnetic susceptibility of infected RBCs with respect to blood plasma. A matrix of nickel posts fabricated in a silicon chip placed face down is aimed at attracting infected cells, while healthy cells sediment on a glass slide under the action of gravity. Using a model of infected RBCs, that is, erythrocytes with methemoglobin, we obtained a capture efficiency of about 70% after 10 min in static conditions. By proper agitation, the capture efficiency reached 85% after just 5 min. Sample preparation requires only a 1:10 volume dilution of whole blood, previously treated with heparin, in a phosphate-buffered solution. Nonspecific attraction of untreated RBCs was not observed in the same time interval.

Since the 1980s, the generation and detection of spin currents has relied on ferromagnets. Their switching today relies on spin-orbit torque from heavy metals. Nevertheless, spin injection in semiconductors has rather low efficiency. Ferroelectric Rashba semiconductors (FERSC) [1,2] may constitute a new paradigm for semiconductor spintronics, thanks to the combination of semiconductivity, large spin-orbit interaction, and the non-volatility provided by ferroelectricity. Here we report the room-temperature ferroelectric switching of spin-to-charge conversion in epitaxial GeTe films. We first show that ferroelectricity in GeTe can be reversed by electrical gating despite its high carrier density. Then, we reveal a spin-to-charge conversion as effective as in Pt, but whose sign switches with the ferroelectric polarization. These results open a route towards devices combining spin-logic and memory integrated into a silicon-compatible material.

A novel frequency modulated MEMS magnetometer is presented. The new device is inspired by the magnetic force microscopy technique, it combines standard MEMS technology with magnetic elements to obtain a magnetometer with potential for low power consumption and high performance. The analytical model and the characterization of the first proof-concept device are presented., Comment: Accepted version of the paper

Lead-free piezoceramics aiming at replacing the market-dominant Pb(ZrxTi1−x)O3 have been extensively researched for more than a decade worldwide due to the toxicity of lead. In this context, (K0.5Na0.5)NbO3 (KNN) triggered the attention of the scientific community thanks to its bulk record piezoelectric coefficient combined with high critical temperature, which make it a good candidate for applications. In this paper, (001)-oriented KNN thin films grown by pulsed laser deposition on Pt(111)/TiO2/SiO2/Si substrates are investigated. We highlight the relevance of the template substrate in determining the structure of the film. Developing a suitable treatment for the Pt substrate is of great importance to film morphologic and topographic quality and to electric, ferroelectric, and piezoelectric properties. From local characterization of piezoelectric properties, we find a piezoelectric coefficient d33 of about 80 pm/V, comparable to the highest values reported for state-of-the-art undoped KNN thin films. Finally, electrical characterization of fabricated micro-capacitors allows the investigation of dielectric performance and shows remanent ferroelectric polarization over microscopic areas, thus paving the way to the integration of these KNN films in microfabricated actuator devices.

Despite the huge efforts for malaria eradication, this infectious disease still represents a critical issue worldwide, with 3.5 billion people still at risk, 229 million new cases and 409.000 deaths in 2019. The infection is caused by the Plasmodiun parasite which attacks red blood cells, feeds on hemoglobin and transform it into hemozoin nanocrystals. In this paper we report on a novel pan-malaria test (TMek), based on the paramagnetic properties of hemozoin nanocrystals, which allows for the automatic quantification of infected red blood cells (i-RBCs) on a microchip. Exploiting the competition between gravity and magnetic forces, i-RBCs in a whole blood specimen are captured on micromagnetic concentrators and electrically detected, allowing for the measurement of their concentration with a limit of sensitivity down to 10 parasites/μl.

The impact of magnetic domains in magnetic flux concentrators is studied using the simulation software MuMax3. First, the simulation parameters are validated using experimental results from magnetic force microscopy; second the simulation output is benchmarked with the one obtained using Comsol Multiphysics. Finally, the impact of magnetic domain is assessed, showing how micromagnetic effects can become relevant, if not dominant, when scaling the gap between the MFC and the sensor., Comment: this is the accepted manuscript

We developed a biosensing system for serological detection of viruses based on the impedance variation between gold microelectrodes upon the capture of the target antibodies hybridized with nanobeads for signal amplification. The microfluidic platform core features a Differential Impedance Sensing (DIS) architecture between a reference and an active sensor able to reach nanoparticle resolution of few tens. The biosensor, functionalized with a copoly layer housing a synthetic peptide probe, has shown a limit of detection (LOD) below 100 pg/mL using a model IgG antibody spiked in a buffer. The biosensor was also tested with human serum samples for quantitative counts of anti-Dengue Virus antibodies, reaching a sensitivity that outperforms commercial ELISA kit. The system is perfectly suited to be easily reconfigured for novel probes by simply modifying the preparation of the biosensor chip surface, thus addressing a wide range of pathogens and diseases with clinically relevant concentrations for rapid immunoassays in a point of care setting.

Malaria remains the most important mosquito‐borne infectious disease worldwide, with 229 million new cases and 409.000 deaths in 2019. The infection is caused by a protozoan parasite which attacks red blood cells by feeding on hemoglobin and transforming it into hemozoin. Despite the WHO recommendation of prompt malaria diagnosis, the quality of microscopy‐based diagnosis is frequently inadequate while rapid diagnostic tests based on antigens are not quantitative and still affected by non‐negligible false negative/positive results. PCR‐based methods are highly performant but still not widely used in endemic areas. Here, a diagnostic tool (TMek), based on the paramagnetic properties of hemozoin nanocrystals in infected red blood cells (i‐RBCs), is reported on. Exploiting the competition between gravity and magnetic forces, i‐RBCs in a whole blood specimen are sorted and electrically detected in a microchip. The amplitude and time evolution of the electrical signal allow for the quantification of i‐RBCs (in the range 10–105 i‐RBC µL−1) and the distinction of the infection stage. A preliminary validation study on 75 patients with clinical suspect of malaria shows on‐field operability, without false negative and a few false positive results. These findings indicate the potential of TMek as a quantitative, stage‐selective, rapid test for malaria., Malaria is caused by the Plasmodium parasite which feeds on hemoglobin and produces paramagnetic hemozoin crystals within red blood cells (RBCs). A quantitative and stage‐selective pan‐malaria diagnostic test is disclosed, based on a simple concept implemented on a microchip: the sorting and electrical detection of infected RBCs, thanks to the competition between magnetic and gravity forces.

Publisher Copyright: © 2021 The Author(s). Published by IOP Publishing Ltd. Magnonics is a budding research field in nanomagnetism and nanoscience that addresses the use of spin waves (magnons) to transmit, store, and process information. The rapid advancements of this field during last one decade in terms of upsurge in research papers, review articles, citations, proposals of devices as well as introduction of new sub-topics prompted us to present the first roadmap on magnonics. This is a collection of 22 sections written by leading experts in this field who review and discuss the current status besides presenting their vision of future perspectives. Today, the principal challenges in applied magnonics are the excitation of sub-100 nm wavelength magnons, their manipulation on the nanoscale and the creation of sub-micrometre devices using low-Gilbert damping magnetic materials and its interconnections to standard electronics. To this end, magnonics offers lower energy consumption, easier integrability and compatibility with CMOS structure, reprogrammability, shorter wavelength, smaller device features, anisotropic properties, negative group velocity, non-reciprocity and efficient tunability by various external stimuli to name a few. Hence, despite being a young research field, magnonics has come a long way since its early inception. This roadmap asserts a milestone for future emerging research directions in magnonics, and hopefully, it will inspire a series of exciting new articles on the same topic in the coming years.

The development of innovative diagnostic tests is fundamental in the route towards malaria eradication. Here, we discuss the sorting capabilities of an innovative test for malaria which allows the quantitative and rapid detection of all malaria species. The physical concept of the test exploits the paramagnetic property of infected erythrocytes and hemozoin crystals, the magnetic fingerprints of malaria common to all species, which allows them to undergo a selective magnetophoretic separation driven by a magnetic field gradient in competition with gravity. Upon separation, corpuscles concentrate at the surface of a silicon microchip where interdigitated electrodes are placed in close proximity to magnetic concentrators. The impedance variation proportional to the amount of attracted particles is then measured. The capability of our test to perform the selective detection of infected erythrocytes and hemozoin crystals has been tested by means of capture experiments on treated bovine red blood cells, mimicking the behavior of malaria-infected ones, and suspensions of synthetic hemozoin crystals. Different configuration angles of the chip with respect to gravity force and different thicknesses of the microfluidic chamber containing the blood sample have been investigated experimentally and by multiphysics simulations. In the paper, we describe the optimum conditions leading to maximum sensitivity and specificity of the test.

Synthetic antiferromagnets (SAF) are widely used for a plethora of applications among which data storage, computing, and in the emerging field of magnonics. In this framework, controlling the magnetic properties of SAFs via localized thermal treatments represents a promising route for building novel magnonic materials. In this paper, we study via vibration sample magnetometry the temperature dependence of the magnetic properties of sputtered exchange bias SAFs grown via magnetron sputtering varying the ferromagnetic layers and spacer thickness. Interestingly, we observe a strong, reversible modulation of the exchange field, saturation field, and coupling strength upon heating up to 250 &deg, C. These results suggest that exchange bias SAFs represent promising systems for developing novel artificial magnetic nanomaterials via localized thermal treatment.

In this paper, we report on the magnetic and chemical characterization of the exchange-biased CoFeB/IrMn bilayers, grown by magnetron sputtering on a Si-based platform and capped by either a Ru or MgO/Ru overlayer. For Ru capping, the blocking temperature monotonously increases with the IrMn thickness within the investigated range (3.5–8 nm). On the contrary, for MgO/Ru capping, the exchange bias is inhibited below 6 nm, whereas above 6 nm, the magnetic behavior is the same of Ru-capped films. The chemical analysis reveals a significant dependence of the Mn content from the capping layer for thin IrMn films (2.5 nm), whereas the difference disappears when IrMn becomes thick (7 nm). Our work suggests that a non-uniform composition of the IrMn films directly affects the exchange coupling at the IrMn/CoFeB interface.

In vivo, cells are frequently exposed to multiple mechanical stimuli arising from the extracellular microenvironment, with a deep impact on many biological functions. On the other hand, current methods for mechanobiology do not allow one to easily replicate in vitro the complex spatio-temporal profile of such mechanical signals. Here we introduce a new platform for studying the mechanical coupling between single cells and a dynamic extracellular environment, based on active substrates for cell culture made of Fe-coated polymeric micropillars. Under the action of quasi-static external magnetic fields, each group of pillars produces synchronous mechanical stimuli at different points of the cell membrane, thanks to the highly controllable pillars' deflection. This method allows one to apply complex stress fields, resulting in the parallel application of localized forces with tunable intensity and temporal profile. The platform has been validated by studying the cellular response to periodic stimuli in NIH3T3 fibroblasts. We find that low-frequency mechanical stimulation affects the actin cytoskeleton, nuclear morphology, and H2B core-histone dynamics and induces MKL transcription-cofactor translocation from nucleus to cytoplasm. The unique capability of the proposed platform to apply stimuli with a tunable temporal profile and high parallelism on a cell culture holds great potential for the investigation of mechanotransduction mechanisms in cells and tissues.

In recent years, the development of portable platforms for performing fast and point-of-care analyses has drawn considerable attention for their wide variety of applications in life science. In this framework, tools combining magnetoresistive biosensors with magnetic markers have been widely studied in order to detect concentrations of specific molecules, demonstrating high sensitivity and ease of integration with conventional electronics. In this work, first, we develop a protocol for efficient hybridization of natural DNA; then, we show the detection of hybridization events involving natural DNA, namely genomic DNA extracted from the pathogenic bacterium Listeria monocytogenes, via a compact magnetic tunneling junction (MTJ)-based biosensing apparatus. The platform comprises dedicated portable electronic and microfluidic setups, enabling point-of-care biological assays. A sensitivity below the nM range is demonstrated. This work constitutes a step forward towards the development of portable lab-on-chip platforms, for the multiplexed detection of pathogenic health threats in food and food processing environment.

By performing density functional theory and Green's functions calculations, complemented by x-ray photoemission spectroscopy, we investigate the electronic structure of Fe/GeTe(111), a prototypical ferromagnetic/Rashba-ferroelectric interface. We reveal that such a system exhibits several intriguing properties resulting from the complex interplay of exchange interaction, electric polarization, and spin-orbit coupling. Despite a rather strong interfacial hybridization between Fe and GeTe bands, resulting in a complete suppression of the surface states of the latter, the bulk Rashba bands are hardly altered by the ferromagnetic overlayer. This could have a deep impact on spin-dependent phenomena observed at this interface, such as spin-to-charge interconversion, which are likely to involve bulk rather than surface Rashba states.

Interfaces play a crucial role in the study of novel phenomena emerging at heterostructures comprising metals and functional oxides. In this work, we consider Cr/BaTiO3 heterostructures grown on Nb:SrTiO3 (0 0 1) substrates. Chromium thin films with 2 nm nominal thickness are deposited by molecular beam epitaxy on the BaTiO3 layer, and subsequently annealed in vacuum at temperatures ranging from 800 K to 970 K, and finally exposed to 10−7 torr of molecular oxygen for 300 s. Highly ordered films are obtained for each of this condition, ranging from metallic Cr to insulating Cr2O3 with tetragonal structure. Quite unexpectedly, an intermediate – fully ordered – case exists, with the co-presence of Cr and Cr2O3 compounds, each one with its proper crystal orientation. These results show the opportunity of controlling the metal/oxide state of crystalline Cr films grown onto the ferroelectric template BaTiO3/Nb:SrTiO3.

High-performing hybridization platforms fabricated by reactive microcontact printing of DNA probes are presented. Multishaped PDMS molds are used to covalently bind oligonucleotides over a functional copolymer (DMA-NAS-MAPS) surface. Printed structures with minimum width of about 1.5 mu m, spaced by 10 mu m, are demonstrated, with edge corrugation lower than 300 nm. The quantification of the immobilized surface probes via fluorescence imaging gives a remarkable concentration of 3.3 X 103 oligonudeotides/mu m(2), almost totally active when used as probes in DNA-DNA hybridization assays. Indeed, fluorescence and atomic force microscopy show a 95% efficiency in target binding and uniform DNA hybridization over printed areas.

This work presents a platform for the detection of the neuronal magnetic signal arising from the propagation of the action potential along the axon, via an array of highly sensitive magnetoresistive sensors and a low noise front-end electronic setup. We report the results of calculations and experiments for estimating the limit of detection of such platform in terms of minimum detectable magnetic field. Furthermore, an experimental setup for recording the magnetic signal in a brain slice is presented.

Integrated optically inspired wave-based processing is envisioned to outperform digital architectures in specific tasks, such as image processing and speech recognition. In this view, spin waves represent a promising route due to their nanoscale wavelength in the gigahertz frequency range and rich phenomenology. Here, a versatile, optically inspired platform using spin waves is realized, demonstrating the wavefront engineering, focusing, and robust interference of spin waves with nanoscale wavelength. In particular, magnonic nanoantennas based on tailored spin textures are used for launching spatially shaped coherent wavefronts, diffraction-limited spin-wave beams, and generating robust multi-beam interference patterns, which spatially extend for several times the spin-wave wavelength. Furthermore, it is shown that intriguing features, such as resilience to back reflection, naturally arise from the spin-wave nonreciprocity in synthetic antiferromagnets, preserving the high quality of the interference patterns from spurious counterpropagating modes. This work represents a fundamental step toward the realization of nanoscale optically inspired devices based on spin waves.

According to World Health Organization(WHO), 3.2 billion people are at risk for malaria. In 2015, 212 million new cases and 429000 deaths were estimated [1, 2]. Despite treatment in the early stage of the disease is usually very effective, conventional diagnostic tests via optical microscopy examination of thick and thin blood smears are unsuitable for an effective screening of the population. On the other hand, the over-treatment of the disease due to the large percentage of false positives in currently available rapid diagnostic tests (RDTs) may increase the risk of drug resistance. In this scenario, there is a strong need of novel RTDs with (i) the same sensitivity of the gold standard (optical microscopy examination) and (ii) a reduced number of false positives. To fulfill the last requirement, a real improvement would be to move from the detection of antigens or antibodies, which can be hardly washed out in a patient living in an endemic zone even after many weeks from the last malaria episode, to the quantification of infected red blood cells in a blood smear (i-RBC). This essentially means to go back to the concept of gold standard tests, with the additional requirement of integrating i-RBC counting in lab-on-chip platforms suitable for low-cost, rapid and on-site wide screening of the population in endemic zones. It is well known that i-RBCs display a paramagnetic behavior with respect to blood plasma, so that they can be separated from healthy ones and other corpuscles in a high magnetic field gradient. [3] This is due to the fact that, during the intra-erythrocytic development, the parasite degrades hemoglobin into free heme. This molecule, highly toxic to the parasite, is converted in an insoluble form, known as hemozoin or malaria pigment, which crystallizes into paramagnetic nanocrystals found both within the i-RBCs and free in the blood, after RBCs lysis. Of course, both the concentration of free hemozoin crystals and i-RBCs can be used for the determination of the parasitemia. In this paper we present an on-chip magnetophoretic platform for the separation and concentration of i-RBC and hemozoin nanocrystals on pre-defined areas of a chip. This is a pre-requisite for the quantification of the relative percentage of i-RBC with respect to healthy ones (parasitemia) with high sensitivity. The blood drop is placed on a glass substrate, which is then put in close contact to the surface of a chip with Nickel micropillars, at a distance defined by an outer ring which defines also the volume of the cell where magnetophoretic separation takes place. The chip is placed face-down, so that magnetic attraction towards the nickel pillars, in the macroscopic field gradient produced by an external system of permanent magnets, opposes the gravity. In this configuration, i-RBCs and hemozoin crystals are attracted upwards, towards the micropillars, while non-infected erythrocytes and the other blood cells (i.e. white blood cells and platelets) sediment towards the glass substrate. Our design allows to obtain a macroscopic field gradient as high as $1\times 10 ^{15}$ A2/m3 up to a distance of 500 micron from the chip surface, strong enough to overcome gravity and attract i-RBCs and hemozoin crystals towards the chip surface. The chip consists of an array of Ni pillars, with 20–30 micron diameter and 20 micron height, fabricated by electroplating and arranged on a hexagonal closed packed lattice. In close proximity to the chip surface, Ni pillars produce a much stronger field gradient, up to $3\times 10 ^{16}$ A2/m3 at a few microns from their surface, which concentrate the i-RBCs and hemozoin crystals. We have tested this system using RBCs from bovine blood, treated with NaNO 2 in order to induce the transformation of hemoglobin into paramagnetic meta-hemoglobin. [4] In this way, we obtained suspensions in PBS of RBCs mimicking i-RBCs, suitable for experiments of capture. In figure 1 we report optical images from experiments performed in a direct configuration, where gravity and magnetic forces act in the same direction. Untreated RBCs (ut-RBCs) and treated ones with NaNO2 (t-RBCs) were stained with a red fluorophore to improve the quality of optical images. As evident from Figure 1, in case of t-RBCs we observed a capture efficiency of 100% by magnetic pillars in a lattice with center to center spacing of 80 microns. For hemozoin crystals the capture is even easier, because of their much larger volume susceptibility, $3.4\times 10 ^{-4}$ to be compared with $3.9\times 10 ^{-6}$ in case of i-RBCs. These results pave the way to the use of our magnetic chips as active slides for the magnetophoretic separation and concentration of malaria markers, both i-RBCs and hemozoin crystals, in well-defined areas of the chips where quantification can be performed with high sensitivity.

Ferroelectric tunnel junctions are promising candidates for the realization of energy-efficient digital memories and analog memcomputing devices. In this work, we investigate the impact of a semiconducting layer in series to the junction on the sign of electroresistance. To this scope, we compare tunnel junctions fabricated out of Pt/BaTiO3/La1/3Sr2/3MnO3 (LSMO) and Pt/BaTiO3/Nb:SrTiO3 (Nb:STO) heterostructures, displaying an opposite sign of the electroresistance. By capacitance-voltage profiling, we observe a behavior typical of Metal-Oxide-Semiconductor tunnel devices in both cases but compatible with the opposite sign of charge carriers in the semiconducting layer. While Nb:STO displays the expected n-type semiconducting character, metallic LSMO develops an interfacial p-type semiconducting layer. The different types of carriers at the semiconducting interfaces and the modulation of the depleted region by the ferroelectric charge have a deep impact on electroresistance, possibly accounting for the different sign observed in the two systems.Ferroelectric tunnel junctions are promising candidates for the realization of energy-efficient digital memories and analog memcomputing devices. In this work, we investigate the impact of a semiconducting layer in series to the junction on the sign of electroresistance. To this scope, we compare tunnel junctions fabricated out of Pt/BaTiO3/La1/3Sr2/3MnO3 (LSMO) and Pt/BaTiO3/Nb:SrTiO3 (Nb:STO) heterostructures, displaying an opposite sign of the electroresistance. By capacitance-voltage profiling, we observe a behavior typical of Metal-Oxide-Semiconductor tunnel devices in both cases but compatible with the opposite sign of charge carriers in the semiconducting layer. While Nb:STO displays the expected n-type semiconducting character, metallic LSMO develops an interfacial p-type semiconducting layer. The different types of carriers at the semiconducting interfaces and the modulation of the depleted region by the ferroelectric charge have a deep impact on electroresistance, possibly accounting for the dif...

The search of novel tools controlling the physical and chemical properties of matter at the nanoscale is crucial for developing next-generation integrated systems, with applications ranging from computing to medicine. Here, we show that thermal scanning probe lithography (t-SPL) can be a flexible tool for manipulating with nanoscale precision the surface properties of a wide range of specifically designed systems. In particular, we show that via t-SPL, we pattern nanoscale chemical patterns on polymeric substrates, which are then used to specifically bind extracellular matrix (ECM) proteins to the polymer surface. We demonstrate that the concentration of immobilized proteins can be controlled by varying the tip temperature, so that nanoscale protein gradients can be created. On a different system, we show that, by performing t-SPL on a thin film magnetic multilayer, in an external magnetic field, we are able to write reversibly magnetic patterns with arbitrarily oriented magnetization and tunable magnetic anisotropy. This demonstrates that t-SPL represents a novel, straightforward and extremely versatile method for the nanoscale engineering of the physicalchemical properties in a wide variety of materials.

Domain switching in polycrystalline BaTiO3 is exploited to realize self-holding phase actuators in Si-photonics. A non-volatile change of the BaTiO3 refractive-index is achieved and poly-BaTiO3-coated silicon photonic circuits are demonstrated.

The electric and nonvolatile control of the spin texture in semiconductors would represent a fundamental step toward novel electronic devices combining memory and computing functionalities. Recently, GeTe has been theoretically proposed as the father compound of a new class of materials, namely ferroelectric Rashba semiconductors. They display bulk bands with giant Rashba-like splitting due to the inversion symmetry breaking arising from the ferroelectric polarization, thus allowing for the ferroelectric control of the spin. Here, we provide the experimental demonstration of the correlation between ferroelectricity and spin texture. A surface-engineering strategy is used to set two opposite predefined uniform ferroelectric polarizations, inward and outward, as monitored by piezoresponse force microscopy. Spin and angular resolved photoemission experiments show that these GeTe(111) surfaces display opposite sense of circulation of spin in bulk Rashba bands. Furthermore, we demonstrate the crafting of nonvolatile ferroelectric patterns in GeTe films at the nanoscale by using the conductive tip of an atomic force microscope. Based on the intimate link between ferroelectric polarization and spin in GeTe, ferroelectric patterning paves the way to the investigation of devices with engineered spin configurations.

Integrated Mach-Zehnder interferometers, ring resonators, Bragg reflectors or simple waveguides are commonly used as photonic biosensing elements. They can be used for label-free detection relating the changes in the optical signal in realtime, as optical power or spectral response, to the presence and even the quantity of a target analyte on the surface of the photonic waveguide. The label-free method has advantages in term of sample preparation but it is more sensitive to spurious effects such as temperature and refractive index sample variation, biological noise, etc. Label methods can be more robust, more sensitive and able to manipulate the biological targets. In this work, we present an innovative labeled biosensing technique exploiting magnetic nano-beads for enhancement of sensitivity over integrated optic microrings. A sandwich binding is exploited to bring the magnetic labels close to the surface of the optical waveguide and interact with the optical evanescent field. The proximity and the quantity of the magnetic nano-beads are seen as a shift in the resonance of the microring. Detection of antibodies permits to reach a high level of sensitivity, down to 8 pM with a high confidence level. The sizes of the nano-beads are 50 to 250 nm. Furthermore, time-varying magnetic fields permit to manipulate the beads and even induce specific signals on the detected light to easy the processing and provide a reliable identification of the presence of the desired analyte. Multiple analytes detection is also possible.

Spin-orbit coupling effects in materials with broken inversion symmetry are responsible for peculiar spin textures. Among them, ferroelectric materials allow for non-volatile control of the spin degree of freedom through the non-volatile electrical inversion of the spin texture, through to their reversible spontaneous polarization. Such functionality holds potential for technological applications exploiting spin effects controlled by electric fields. The ferroelectric Rashba semiconductor Germanium Telluride stands out as material for Spin-Orbitronics: its ferroelectricity provides a nonvolatile state variable able to generate and drive a giant bulk Rashba-type spin splitting of the electronic bands, while its semiconductivity would allow for the realization of spin-based transistors. The ferroelectric control of the bands topology and of the spin texture is expected to reflect in the tunability of the spin transport properties. Here we exploit the unidirectional spin Hall magnetoresistance of Fe/GeTe heterostructures to characterize charge-to-spin conversion in GeTe. Our preliminary results indicate a sizable conversion efficiency at low temperature (120 K), which promotes ferroelectric Rashba semiconductors as promising candidates for the implementation of non-volatile electrically reconfigurable computing devices based on spin transport in semiconductors.

Methods for the manipulation of single magnetic particles have become very interesting, in particular for in vitro biological studies. Most of these studies require an external microscope to provide the operator with feedback for controlling the particle motion, thus preventing the use of magnetic particles in high-throughput experiments. In this paper, a simple and compact system with integrated electrical feedback is presented, implementing in the very same device both the manipulation and detection of the transit of single particles. The proposed platform is based on zig-zag shaped magnetic nanostructures, where transverse magnetic domain walls are pinned at the corners and attract magnetic particles in suspension. By applying suitable external magnetic fields, the domain walls move to the nearest corner, thus causing the step by step displacement of the particles along the nanostructure. The very same structure is also employed for detecting the bead transit. Indeed, the presence of the magnetic particle in suspension over the domain wall affects the depinning field required for its displacement. This characteristic field can be monitored through anisotropic magnetoresistance measurements, thus implementing an integrated electrical feedback of the bead transit. In particular, the individual manipulation and detection of single 1-μm sized beads is demonstrated.

Pt/BaTiO3/La0.7Sr0.3MnO3 tunnel junctions, at negative voltage bias, for two polarization directions are represented. It is demonstrated that reversing the polarization direction of a ferroelectric barrier in a tunnel junction leads to a change of junction conductance and capacitance, with concomitant variations on the barrier height and effective thickness, both contributing to produce larger electroresistance.

Magnetoencephalography (MEG) has revolutionized neuroscience, offering a tool with unprecedented spatial and temporal resolution. Today, MEG has clinical uses in detecting and localizing pathological activity in patients with brain tumors or intractable epilepsy [1]. Despite the wide clinical applications, the nature of MEG signals at local level is still not well understood [2]. In this context, there is evident crucial interest in developing a new generation of devices for local magnetic recording for an in vitro system. Several recent studies have implied that MagnetoResistive (MR) technologies can detect a biological magnetic field at local scale [3,4] (i.e., brain slice, muscle in vitro). However, to date, no attempts have been carried out for neurons in culture due to the long-term biocompatibility required. In this work, we will present a platform based on MR sensors array, namely magnetic tunneling junctions (MTJs) to detect the activity of neurons in culture from a magnetic point of view. We will show the biocompatibility of our devices and the preservation of the physical properties of the sensors. Murine embryonic hippocampal neurons were grown on top of the MR sensors array. We achieve a lifetime of the on-chip neuronal networks of longer than 20 days. Neurite growth was studied during development with immunostaining analysis. In conclusion, we achieved the biocompatibility conditions of a MR platform suitable for studying the magnetic field generated by the activity of in vitro neuronal networks.

A promising strategy to get deeper insight on brain functionalities relies on the investigation of neural activities at the cellular and sub-cellular level. In this framework, methods for recording neuron electrical activity have gained interest over the years. Main technological challenges are associated to finding highly sensitive detection schemes, providing considerable spatial and temporal resolution. Moreover, the possibility to perform non-invasive assays would constitute a noteworthy benefit. In this work, we present a magnetoresistive platform for the detection of the action potential propagation in neural cells. Such platform allows, in perspective, the in vitro recording of neural signals arising from single neurons, neural networks and brain slices.

Magnonics is envisioned to enable highly efficient data transport and processing, by exploiting propagating perturbations in the spin-texture of magnetic materials. Despite the demonstrations of a plethora of proof-of-principle devices, the efficient excitation, transport and manipulation of spin-waves at the nanoscale is still an open challenge. Recently, we demonstrated that the spin-wave excitation and propagation can be controlled by nanopatterning reconfigurable spin-textures in a continuous exchange biased ferromagnetic film. Here, we show that by patterning 90° stripe-shaped magnetic domains, we spatially modulate the spin-wave excitation in a continuous film, and that by applying an external magnetic field we can reversibly “switch-off” the spin-wave excitation. This opens the way to the use of nanopatterned spin-textures, such as domains and domain walls, for exciting and manipulating magnons in reconfigurable nanocircuits.

In the last years, magnetoresistive biosensors arrays have drawn a great interest due to their high sensitivity and integrability in lab-on-chip platforms. In such devices, the selective functionalization of the sensor active area is a major issue, in order to achieve high sensitivity and quantification capability. Here, we present a straightforward photolithographic procedure to create patterns of bio-reactive polymer regions on the sensor's surface, with micrometric resolution. The effectiveness of the procedure in providing high specificity and improved sensor performance is demonstrated in the case of magnetoresistive biosensors based on magnetic tunneling junctions (MTJs). On-chip biomolecular recognition assays demonstrate an enhanced sensitivity in selectively functionalized sensors with respect to non-patterned sensors, eventually leading to a limit of detection below the pM range, without target pre-concentration or chemical amplification.

In this work, a new method to functionalize a gold surface by dip coating with a functional copolymer is presented. The coating procedure is simple, robust and can be accomplished in less than one hour. Atomic force microscopy (AFM) scratch tests reveal the presence of a homogeneous polymer coating with a thickness of 2.5 nm. X-ray photoemission spectroscopy spectra from C1s, N1s and O1s levels present the typical fingerprints of the polymeric overlayer, i.e. the characteristic peaks from CNCO and NCO groups. Surface plasmon resonance (SPR) binding assays were used to check the coating functional properties. Immobilization of heparin to SPR gold surfaces functionalized with copoly(DMA-NAS-MAPS)- followed by binding analysis with the well known heparin binding protein fibroblast growth factor 2 yield binding kinetic parameters comparable to those obtained with commercially available carboxymethyl dextran-functionalized sensorchips, thus confirming the great potential of the proposed technique. © 2013 Elsevier B.V. All rights reserved.