Self-assemblies of tunable units are being intensively studied as physical systems with signal-processing capabilities. Specifically, silver nanowire networks (AgNWNs) have demonstrated accumulation, non-linearity, and memory retention with multiple timescales, features that enable a wide variety of neuromorphic implementations. In this study, we aim to extract the interconnection scheme to analyze the experimentally obtained network architecture and, eventually, use it as input to a previously developed simulation platform. By post-processing photomicrographs of AgNWN, we present a pipeline optimized to extract the interconnection diagram, recognizing the intersections formed among the nanowires, to determine the associated graph for each physical sample. A graph is a collection of nodes and edges whose properties can be associated with different electrical responses. It is thus possible to study graphs' metrics, such as the degree distribution, community size, clustering coefficient, and path-length, to compare the experimental assemblies' attributes to those of topological models of reference. Small-world, modular, and scale-free are well-known structures in the field of mathematical graphs. By analyzing the degree distribution, the adjacency matrices, among other useful representation means, the experimental assemblies reveal similarities to both small-world and modular topologies. All the mentioned analyses were conducted considering the interconnection scheme obtained from zenithal-view optical images, which overestimates the number of NWs' interconnections (due to the impossibility of distinguishing real junctions from spurious cross-points between vertically displaced NWs). For that reason, this communication also studies the impact of artificially removing junctions from the resulting graphs on the previously calculated clustering coefficient and path length.

ABSTRACT In‐materia processing offers a new paradigm for computing by enabling learning capacity and pattern recognition directly within a physical substrate. We report the development of a 3D nanowire network formed by a polyvinylpyrrolidone matrix embedded with silver nanowires, tailored for neuromorphic applications. Compared to conventional 2D networks, these nanocomposite films lower the switching voltage by effectively increasing the population of filamentary junctions. The polymer's intrinsic hygroscopic properties enhance hydration, acting as a dynamic humidity‐responsive reservoir that facilitates silver ion mobility and modulates resistive switching. Under elevated relative humidity (RH), the film exhibits reversible swelling and enhanced ion mobility, reducing the threshold voltage required to activate conductance. Once activated at high RH, the conductive state remains highly sensitive when returning to lower RH, providing an encoding strategy for retaining information. Multi‐electrode devices were fabricated to demonstrate spatial switching dynamics, short‐term memory, and associative learning tasks. Finally, an epoxy‐resin encapsulation strategy is proposed to preserve hydration and stabilize the neuromorphic performance under diverse environmental conditions. The synergistic combination of a 3D nanocomposite network with hydration‐assisted ion transport offers a promising route toward adaptive, energy‐efficient neuromorphic devices.

We report an unconventional resistive switching effect on high-density self-assembled Ag-nanowire networks tailored by a fuse-like operation. We propose a mechanism to rationalize the observed phenomenology by analyzing the electrical signatures before and after such a fusing. The explanation allows reconciling the results obtained in similar systems early adopted as transparent electrodes and the more recent attempts to use this type of substrate for in-materia computational operations. In addition to the usual analog nature of the available resistance states and the ability to tune internal weights, we show that these networks' sparsity and non-linear behavior are also attributes. Thus, the formerly exhibited nanowires' abilities to code synaptic behavior are complemented by neuronal features upon properly tuning the network density and the applied electrical protocol.

Patterns of ferroic domains and domain walls are being intensively studied to implement new logic schemes. Any technological application of such objects depends on a detailed understanding of them. Using low-temperature magnetic force measurements (10-300 K), the evolution of ferromagnetic stripes on equiatomic FePt thin films is thoroughly analyzed. Since FePt is known to develop a transition from in-plane homogeneous magnetization to stripe domains upon varying its thickness, multiple samples are studied demonstrating the well-established reduction upon thickness decrease and a non-trivial dependence on temperature. Moreover, the room-temperature uniform distribution of the pattern evolves into a distorted one upon temperature cycling. Finally, dissimilar stripe patterns are obtained upon reducing and increasing temperature indicating the states are dependent on the history of applied stimuli rather than the parametric conditions.

Random networks offer fertile ground for achieving complexity and criticality, both crucial for an unconventional computing paradigm inspired by biological brains' features. In this work, we focus on characterizing and modeling different electrical transport regimes of self-assemblies of silver nanowires (AgNWs). As percolation plays an essential role in such a scenario, we explore a broad range of areal density coverage. Close-to-percolation realizations (usually used to demonstrate neuromorphic computing capabilities) have large pristine resistance and require an electrical activation. Up to now, highly conductive over-percolated systems (commonly used in electrode fabrication technology) have not been thoroughly considered for hardware-based neuromorphic applications, though biological systems exhibit such an extremely high degree of interconnections. Here, we show that high current densities in over-percolated low-resistance AgNW networks induce a fuse-type process, allowing a switching operation. Such electro-fusing discriminates between weak and robust NW-to-NW links and enhances the role of filamentary junctions. Their reversible resistive switching enable different conductive paths exhibiting linear I-V features. We experimentally study both percolation regimes and propose a model comprising two types of junctions that can describe, through numerical simulations, the overall behavior and observed phenomenology. These findings unveil a potential interplay of functionalities of neuromorphic systems and transparent electrodes.

Patterns of ferroic domains and domain walls are being intensively studied to implement new logic schemes. Any technological application of such objects depends on a detailed understanding of them. This study analyzes patterns of ferromagnetic stripes on equiatomic FePt thin films at low temperatures. Since FePt is known to develop a transition from in-plane homogeneous magnetization to stripes upon varying its thickness, multiple samples are studied to consider the critical value within the analyzed range. Stripes' width demonstrates the well-known Murayama's law while a non-trivial dependence on temperature is also reported. Moreover, the room-temperature uniform distribution of the pattern evolves into a distorted one upon temperature cycling. Finally, dissimilar striped patterns are obtained upon reducing and increasing temperature indicating the states are dependent on the history of applied stimuli rather than the parametric conditions.

Electronic conduction along individual domain walls (DWs) is reported in BiFeO3 (BFO) and other nominally insulating ferroelectrics. DWs in these materials separate regions of differently oriented electrical polarization (domains) and are just a few atoms wide, providing self‐assembled nanometric conduction paths. Herein, it is shown that electronic transport is possible also from wall‐to‐wall through the dense network of as‐grown DWs in BFO thin films. Electric field cycling at different points of the network, performed locally by conducting atomic force microscopy (cAFM), induces resistive switching selectively at the DWs, both for vertical (single wall) and lateral (wall‐to‐wall) conduction. These findings are the first step toward investigating DWs as memristive networks for information processing and in-materio computing.

Self-assembled structures are possible solutions to the problem of increasing the density and connectivity of memristive units in massive arrays. Although they would allow surpassing the limit imposed by the lithographic feature size, the spontaneous formation of highly interconnected networks poses a new challenge: how to characterize and control the obtained assemblies. In view of a flourishing field of such experimental realizations, this study explores the collective electrical response of simulated memristive units when assembled in geometrically organized and progressively distorted configurations. We show that highly idealized memristive arrays already display a degree of complexity that needs to be taken into account when characterizing self-assemblies to be technologically exploited. Moreover, the introduction of simple distortions has a considerable impact on the available resistance states and their evolution upon cycling. Considering arrays of a limited size, we also demonstrate that the collective response resembles aspects of the individual model while also revealing its own phenomenology.

Percolating networks formed by coated metallic nanowires have recently shown to exhibit memristive properties, opening a path for the development of neuromorphic systems. In this work, the resistive switching phenomena occurring in percolative networks of silver nanowires (AgNWs) coated with a thin layer of polyvinylpyrrolidone is studied. By performing voltage‐driven excursions, the highly‐conductive pristine state irreversibly changes to a higher resistance state. Such an electroforming procedure enables the switching among multiple resistance states. The stability and controllability of the resistance levels are found to be highly dependent on the initial state and the environmental conditions. In low relative humidity environments, the system displays the most controlled switching operation, while in high humidity environments the system shows a high conductance level. Samples with hysteretic response display sharp and spontaneous transitions to different resistance states, exhibiting multilevel memory device features. Both behaviors can be associated with regions of high local concentration of AgNWs that can couple or decouple from the conduction paths according to external stimuli. Conductivity is determined at a fundamental level by electrochemical processes at critical junctions in which water molecules play a key role. These results are relevant for the development of AgNWs‐based electronics and in‐hardware neuromorphic computing.

Originally studied for their suitability to store information compactly, memristive networks are now being analysed as implementations of neuromorphic circuits. An extremely high number of elements is thus mandatory. To surpass the limited achievable connectivity - due to the featuring size - exploiting self-assemblies has been proposed as an alternative, in turn posing more challenges. In an attempt for offering insight on what to expect when characterizing the collective electrical response of switching assemblies, in this work, networks of memristive elements are simulated. Collective electrical behaviour and maps of resistance states are characterized upon different electrical stimuli. By comparing the response of homogeneous and heterogeneous networks, we delineate differences that might be experimentally observed when the number of memristive units is scaled up and disorder arises as an inevitable feature.

BaBiO$_3$ is a charged ordered Peierls-like perovskite well known for its superconducting properties upon K or Pb doping. We present a study on the transport and electronic properties of BaBiO$_3$ perovskite with strong Bi-deficiency. We show that it is possible to synthesize BaBiO$_3$ thin layers with Bi-vacancies above 8-10% by depositing an yttrium-stabilized zirconia capping layer. By combining transport measurements with ab initio calculations we propose an scenario where the Bi-vacancies give rise to the formation of polarons and suggest that the electrical transport is dominated by the migration of these polarons trapped at Bi$^{3+}$ sites. Our work shows that cation vacancies engineering -- hardly explored to date -- appears as a promising pathway to tune the electronic and functional properties of perovskites.

Originally studied for their suitability to store information compactly, memristive arrays are now being analysed as implementations of neuromorphic systems. Nevertheless, the achievable interconnectivity is usually limited by the featuring size of each technological era. An alternative strategy is to exploit self-assembled arrays of potential memristive units. To bridge the gap between models of individual memristive units and how to take advantage of experimental self-assemblies, in this work, arrays of memristive devices are simulated and the overall response is characterized upon different electrical stimuli. By comparing the response of uniform and homogeneous arrays (ideal) with non-uniform and heterogeneous ones (distorted), we delineate differences that might be experimentally observed when the number of memristive units is scaled up and disorder arises as an inevitable feature.

The creep motion of domain walls driven by external fields in magnetic thin films is described by universal features related to the underlying depinning transition. One key parameter in this description is the roughness exponent characterizing the growth of fluctuations of the domain wall position with its longitudinal length scale. The roughness amplitude, which gives information about the scale of fluctuations, however, has received less attention. Albeit their relevance, experimental reports of the roughness parameters, both exponent and amplitude, are scarce. We report here experimental values of the roughness parameters for different magnetic field intensities in the creep regime at room temperature for a Pt/Co/Pt thin film. The mean value of the roughness exponent is zeta = 0.74, and we show that it can be rationalized as an effective value in terms of the known universal values corresponding to the depinning and thermal cases. In addition, it is shown that the roughness amplitude presents a significant increase with decreasing field. These results contribute to the description of domain wall motion in disordered magnetic thin systems.

Memristive devices made of silicon compatible simple oxides are of great interest for storage and logic devices in future adaptable electronics and non-digital computing applications. A series of highly desirable properties observed in an atomic-layer-deposited hafnia-based stack, triggered our interest to investigate their suitability for technological implementations. In this paper, we report our attempts to reproduce the observed behaviour within the framework of a proposed underlying mechanism. The inability of achieving the electrical response of the original batch indicates that a key aspect in those devices has remained undetected. By comparing newly made devices with the original ones, we gather some clues on the plausible alternative mechanisms that could give rise to comparable electrical behaviours.

Understanding the effect of fabrication conditions on domain wall (DW) motion in thin films with perpendicular magnetization is a mandatory issue in order to tune their properties aiming to design spintronics devices based on such phenomenon. In this context, the present work intends to show how different growth conditions may affect DW motion in the prototypical system Pt/Co/Pt. The trilayers were deposited by dc sputtering, and the parameters varied in this study were the Co thickness, the substrate roughness and the base pressure in the deposition chamber. Magneto-optical Kerr effect-based magnetometry and microscopy combined with x-ray reflectometry, atomic force microscopy and transmission electron microscopy were adopted as experimental techniques. This permitted us to elucidate the impact on the hysteresis loops and on the DW dynamics, produced by different growth conditions. As other authors, we found that Co thickness is strongly determinant for both the coercive field and the DW velocity. On the contrary, the topographic roughness of the substrate and the base pressure of the deposition chamber evidence a selective impact on the nucleation of magnetic domains and on DW propagation, respectively, providing a tool to tune these properties.

The domain wall response under constant external magnetic fields reveals a complex behavior where sample disorder plays a key role. Furthermore, the response to alternating magnetic fields has only been explored in limited cases and analyzed in terms of the constant field solution. Here we unveil phenomena in the evolution of magnetic domain walls under the application of alternating magnetic fields within the creep regime, well beyond a small fluctuation limit of the domain wall position. Magnetic field pulses were applied in ultrathin ferromagnetic films with perpendicular anisotropy, and the resulting domain wall evolution was characterized by polar magneto-optical Kerr effect microscopy. Whereas the dc characterization is well predicted by the elastic interface model, striking unexpected features are observed under the application of alternating square pulses: Magneto-optical images show that after a characteristic number of cycles, domain walls evolve toward strongly distorted shapes concomitantly with a modification of domain area. The morphology of domain walls is characterized with a roughness exponent when possible and contrasted with alternative observables which are more suitable for the characterization of this transient evolution. The final stationary convergence as well as the underlying physics is discussed.

We report the precise control of tunneling magnetoresistance (TMR) in devices of self-assembled core/shell Fe$_3$O$_4$/Co$_{1-x}$Zn$_x$Fe$_2$O$_4$ nanoparticles ($0\leq x\leq 1$). Adjusting the magnetic anisotropy through the content of Co$^{2+}$ in the shell, provides an accurate tool to control the switching field between the bistable states of the TMR. In this way, different combinations of soft/hard and hard/soft core/shell configurations can be envisaged for optimizing devices with the required magnetotransport response.

Multiferroic tunnel junctions (MFTJs) with Hf0.5Zr0.5O2 barriers are reported to show both tunneling magnetoresistance effect (TMR) and tunneling electroresistance effect (TER), displaying four resistance states by magnetic and electric field switching. Here we show that, under electric field cycling of large enough magnitude, the TER can reach values as large as 10(6)%. Moreover, concomitant with this TER enhancement, the devices develop electrical control of spin polarization, with sign reversal of the TMR effect. Currently, this intermediate state exists for a limited number of cycles and understanding the origin of these phenomena is key to improve its stability. The experiments presented here point to the magneto-ionic effect as the origin of the large TER and strong magneto-electric coupling, showing that ferroelectric polarization switching of the tunnel barrier is not the main contribution.

Atomic layer deposition (ALD) is a standard technique employed to grow thin-film oxides for a variety of applications. We describe the technique and demonstrate its use for obtaining memristive devices. The metal/insulator/metal stack is fabricated by means of ALD-grown HfO2, deposited on top of a highly doped Si substrate with an SiO2 film and a Ti electrode. Enhanced device capabilities (forming free, self-limiting current, non-crossing hysteretic current-voltage features) are presented and discussed. Careful analysis of the stack structure by means of X-ray reflectometry, atomic force microscopy, and secondary ion mass spectroscopy revealed a modification of the device stack from the intended sequence, HfO2/Ti/SiO2/Si. Analytical studies unravel an oxidation of the Ti layer which is addressed for the use of the ozone precursor in the HfO2 ALD process. A new deposition process and the model deduced from impedance measurements support our hypothesis: the role played by ozone on the previously deposited Ti layer is found to determine the overall features of the device. Besides, these ALD-tailored multifunctional devices exhibit rectification capability and long enough retention time to deserve their use as memory cells in a crossbar architecture and multibit approach, envisaging other potential applications.