The integration of high-quality SrTiO 3 thin films on silicon substrates is crucial for various applications.

Lanthanide (Ln3+) coordination complexes featuring only Ln–S bonds have optical properties uniquely modulated by soft donor atoms. Yet, these complexes and their applications are underexplored, due to the stricter environmental control required for their preparation relative to complexes containing Ln–O bonds. Herein, we show that Ln-S coordination is ideally suited to generate information-rich near-infrared (NIR) photoluminescence, laying the optimal ground for machine learning-driven optical sensing. We prepared three new homoleptic complexes with general formula [K(2.2.2-cryptand)][Ln(L)4] (Ln = Nd3+ (1-Nd), Gd3+ (1-Gd), or Yb3+ (1-Yb); L = 2,6-bis-(4-tert-butylphenyl)phenyldithiocarboxylate). In all complexes, the Ln3+ ion is dodecahedrally coordinated to eight sulfur atoms, which exert a moderate, anisotropic ligand field—as unveiled via magnetic measurements and ab initio calculations. Temperature-dependent photoluminescence and optical absorption measurements allowed identifying the electronic transitions and energy transfer mechanisms underpinning the complexes’ optical properties, which are dominated by ligand sensitization of the Ln3+ emission. Survey of the photoluminescence-vs-temperature (calibration) datasets indicated the amenability of 1-Nd and 1-Yb to luminescence thermometry. Chiefly, the complex spectral variations induced by thermal changes can be comprehensively analyzed via Principal Component Analysis, thus extracting global optical features with readout precision that is one order of magnitude higher than classical, local spectral features. More broadly, this study demonstrates that spectral complexity in molecular systems sets the necessary preconditions for advanced optical sensing supported by machine learning algorithms.

The distribution of air pollution in urban environments is greatly influenced by its source and the complexity of the urban environment, which determine the pollution concentrations in individual locations. Traffic is one of the main pollution sources in cities and, especially particulate matter (PM) poses a serious risk for public health. This study applies magnetic biomonitoring using moss bags to establish an extensive urban canopy layer monitoring network (n = 52) to study the distributions and concentrations of magnetic PM. Moss bags were placed at street and roof levels within the grid plan area of Turku, Finland, for 62 days in late autumn. Samples were analysed for mass-specific magnetic susceptibility (χ), hysteresis parameters and elemental components. At street level, traffic was the primary source of magnetic PM and related elements. At higher altitudes, these concentrations were reduced and mainly replaced by crustal elements. Magnetic measurements were also applied to test for equivalence with the CAR-FMI dispersion model and to assess the representativeness of an air quality monitoring station in the city centre. Inconsistencies were observed between the model and magnetic PM concentrations at street level. At rooftop level, the model estimates were higher than indicated by the magnetic PM. The magnetic measurements complemented measurements derived from supplementary monitoring sensors and Turku monitoring station. The representativeness of the monitoring station should be re-evaluated, and recategorizing should be considered. Magnetic biomonitoring using moss bags is an unparalleled tool for monitoring airborne PM pollution and a reliable tool for evaluating monitoring stations and dispersion model performance.

The rapid rise of commercial compact fusion devices has triggered fast-growing demand for high-temperature superconducting tapes, creating a major opportunity for the high-temperature superconducting (HTS) tape industry. Pulsed laser deposition (PLD) has been extensively applied for fabrication of heteroepitaxial HTS wires or tapes based on REBCO-type superconductor, also referred to as, coated conductors (CCs). A combination of multi-plume, multi-turn deposition technique and use of high-power excimer lasers has enabled and accelerated the industrialization of REBCO coated conductors. Currently, the annual production of top-tier PLD-based, HTS-wire manufacturers exceeds 3,000 km-12 mm, contributing to over half of the total global HTS wire production. PLD-REBCO tapes have demonstrated excellent in-field performance (Ic > 200 A-4 mm @20K, 20T, B//c) and competitive pricing (∼$20/m). PLD technology continues to evolve, demonstrating strong competitive advantages. However, challenges remain in further cost reduction, process stability, and increasing efficiency of raw material utilization. AI-based data mining and tackling emerging fundamental issues are seen as potential solutions to further improve stability and performance.

This study explores the area-dependent resistive switching (RS) characteristics of Gd0.2Ca0.8MnO3 (GCMO)-based memristors with aluminum (Al) and gold (Au) electrodes, emphasizing their potential for neuromorphic computing applications. Using a combination of electrical measurements and X-ray photoelectron spectroscopy (XPS), we demonstrate that the high-resistance (HRS) and low-resistance (LRS) states exhibit predictable scaling with device area, with HRS resistances ranging from 107 to 108 Ω and LRS from 105 to 107 Ω, supporting the hypothesis of interface-type RS. XPS depth profiling revealed notable differences in AlO x interfacial layer composition between HRS and LRS, with a higher oxide content and a widened interfacial region in HRS. Additionally, the multistate RS capability of up to ten distinct levels was achieved by modulating applied voltages, highlighting GCMO's suitability as a material for synaptic weight storage in artificial neural networks. Our findings underscore GCMO's promise for energy-efficient, scalable memristor-based systems.

To increase performance of many photonic devices (e.g., solar cell, light emitting diode (LED), photodetector), it is essential to decrease light reflection at device interfaces. Sustainable and scalable methods have been intensively developed for manufacturing nanostructured antireflection coatings at device surfaces to reduce the reflection‐induced losses in them. In this work, a novel wet chemical method is demonstrated to prepare black nanostructured GaAs surfaces in scalable manner. This facile method includes two steps: immersion of GaAs in hot H 2 O 2 solution followed by immersion in hot H 2 O both at around 80 °C. Microscopy, spectroscopy, and diffraction measurements reveal that the H 2 O 2 immersion increases a surface porosity at GaAs while the hot‐water treatment causes the formation of GaOOH nanocrystals. Reflectivity at the resulting black GaAs surface is decreased even below 1% in a broadband. Photoluminescence intensity measurements are used to study whether the presented top‐to‐down method increases harmful non‐radiative recombination, as compared to the initial GaAs surface. Integration of the found black‐GaAs method with device manufacturing is presented by means of planar metal–GaAs–metal photodetectors, of which external quantum efficiency increases due to the method.

Low-resistive Ohmic contacts are needed in most microelectronics and photonics devices to connect a device to the electric circuit. Manufacturing of Ohmic contacts typically requires the doping of a semiconductor surface region as n-type or p-type (i.e., electron- or hole-doped, respectively). This task has, however, become challenging when the doping needs to be controlled with nanometer or even atomic level precision at lowered processing temperatures. In this work, we demonstrate a low-temperature method to tackle this contact manufacturing challenge using ultrathin antimony (Sb) doped germanium (Ge) nanolayers. We have integrated the method with the common lift-off processing to make Ohmic nickel (Ni) contacts on low-doped n-type Ge and Si substrates and on semi-insulating GaAs, which initially show the Schottky contacts. A proper combination of wet chemical cleaning plus depositing Sb and Ge atomic layers on the substrates, kept at room temperature, in a very clean environment of ultrahigh vacuum before the Ni-film deposition and postmetallization heating changes the Schottky contacts to Ohmic ones. Complementary methods are used to probe the physicochemical properties of interfaces during the manufacturing process to clarify the mechanisms behind the Ohmic-contact formation.

Epitaxial Sr2FeMoO6(SFMO) films were investigated for their magnetoresistive properties. The results revealed a distinct anisotropic resistance response to the magnetic field, which was especially noticeable when the current path was oriented along different crystallographic directions. This anisotropic behavior was observed as varying symmetries in the resistance-field direction dependence. The phenomenon was discussed in the context of magnetocrystalline anisotropy as well as more general electrical properties. The findings suggest that some commonly accepted explanations for anisotropic magnetoresistance are insufficient to account for the recent observations. A deeper understanding of the electrical properties of SFMO-and similar materials-is therefore necessary. Additionally, the work demonstrated an enhancement in magnetic properties as a result of temperature annealing treatment.

Polycrystalline silicon (poly-Si) is an excellent material for use in microelectronic devices, both in electrical and mechanical applications. Its mechanical and electrical properties are widely adjustable, its processing technology is compatible with existing microcircuit manufacturing technology, and its availability and recyclability are at a high level. Here, we focus on investigating the properties of poly-Si that distinguish it from other forms of silicon, that is, grains, grain boundaries, and the conditions and treatments that determine grain and grain boundary properties. Starting from the molecular dynamics simulations of the deposition of thin poly-Si films under different growth conditions we study the properties of the films, grains, and grain boundaries as a function of growth time, growth temperature, and post-annealing. We aim to get data and information that will form the essential basis for future research on the electrical properties of poly-Si. The main results are: (i) the effect of post-annealing on the distribution of the grain size and grain boundary thickness (ii) the distribution of the grain orientations, and (iii) the density of the 3- and 5-bonded atoms as a function of deposition temperature.

A method of producing high-quality thin films of perovskite manganites utilizing citrate-based aqueous chemical solution deposition is presented. The method is applied to the production of thin films of gadolinium calcium manganite, Gd1−xCaxMnO3 (GCMO). The film quality is verified by x-ray diffraction analysis, electron microscopy, and magnetic measurements. Finally, planar memristors are fabricated using GCMO films, demonstrating the material’s ability to exhibit resistive switching. This underscores its potential for future memristor technologies.

Polycrystalline silicon (poly-Si) significantly expands the properties of the ICT miracle material, silicon (Si). Depending on the grain size and shape and grain boundary structure, the properties of poly-Si exceed what single-crystal (c-Si) and amorphous (a-Si) silicon can offer, especially for radio frequency (RF) applications in microelectronics. Due to its wide range of applications and, on the one hand, its theoretically and technologically challenging microstructure, poly-Si research is the most timely (Ding et al 2020 Mater. Charact. 161 110174; Zhao and Li 2019 Acta Mater. 168 52-62). In this report, we describe how we simulate and analyse the phenomena and mechanisms that control the effect of poly-Si deposition parameters on the structure of the deposited poly-Si films using classical molecular dynamics simulations. The grain shape and size, degree of crystallinity, grain boundary structure and the stress of poly-Si films are determined depending on the growth temperature, temperature distribution in the growing film, deposition flux, flux variation and the energy transferred to the film surface due to the deposition flux. The main results include: (i) the dependence of the crystallinity profile of the deposited poly-Si films on the stress, temperature and the different parameters of the deposition flux, (ii) growth modes at the early stages of the deposition, (iii) interaction and stability of seed crystallites at the early stage of the deposition of poly-Si films and the transition from the isolated crystallite growth to the poly-Si growth, (iv) interplay of the temperature, crystallinity, crystal shape and heath conductivity of different Si phases, (v) four different stages of crystallite growth are described: nucleation, growth, disappearance and retardation.

Urban areas form a mosaic of microenvironments and structures, such as street canyons that are susceptible to elevated levels of traffic related pollutants. Street canyons are a relevant topic in air quality research and modelling since they are prone to reduced natural ventilation and when exposed to increased traffic emissions, can pose a serious risk to public health. We applied magnetic biomonitoring using moss bags to evaluate the quality of Operational Street Pollution Model (OSPM) and to study vertical distribution of modelled particulate matter (PM), magnetic PM and heavy metal pollution in a street canyon in Turku and Helsinki, Finland. Moss bags were attached on opposite sides of the streets at 3-, 6-, 9-and 12-m heights for 44 days in late autumn. Samples were analysed for mass-specific magnetic susceptibility (chi), hysteresis parameters and elemental components. High chi values and elemental concentrations of Fe, Al, Ti, Zn, Mn, Cu and Ba were found in both street canyons. Compared to measurements with airborne magnetic PM, the OSPM model underestimated the difference in PM concentrations between the opposite street canyon faces and overestimated the dilution of PM concentrations with altitude. In Turku the results between the OSPM model and magnetic measurements were incompatible. We suspect this is due to meteorological model input data from a distant weather station, street canyon features and a high slope angle contributing to non-uniform emissions in the street canyon. We demonstrate that the moss bag technique is a versatile tool to understand the small-scale variations of concentrations in a variety of complex urban environments.

Abstract Manganite-based memristive devices have emerged as promising candidates for next-generation non-volatile memory and neuromorphic computing applications, owing to their unique resistive switching behavior and tunable electronic properties. This review explores recent innovations in manganite-based memristive devices, with a focus on materials engineering, device architectures, and fabrication techniques. We delve into the underlying mechanisms governing resistive switching in manganite thin films, elucidating the intricate interplay of oxygen vacancies, charge carriers, and structural modifications. This review underscores breakthroughs in harnessing manganite memristors for a range of applications, from high-density memory storage to neuromorphic computing platforms that mimic synaptic and neuronal functionalities. Additionally, we discuss the role of characterization techniques and the need for a unified benchmark for these devices. We provide insights into the challenges and opportunities associated with the co-integration of manganite-based memristive devices with more mature technologies, offering a roadmap for future research directions.

The heterogeneous integration of ferroelectric BaTiO3 thin films on silicon (Si) and silicon nitride (SiN)-based platforms for photonic integrated circuits (PICs) plays a crucial role in the development of future nanophotonic thin film modulators. Since the electro-optic (EO) properties of ferroelectric thin films strongly depend on their crystal phase and texture, the integration of BaTiO3 thin films on these platforms is far from trivial. So far, a conventional integration route using a SrTiO3 template film in combination with high vacuum deposition methods has been developed, but it has a low throughput, is expensive and requires monocrystalline substrates. To close this gap, a cost-efficient, high-throughput and scalable method for integrating highly textured BaTiO3 films is needed. Therefore, an alternative method for the integration of highly textured BaTiO3 films using a La2O2CO3 template film in combination with a chemical solution deposition (CSD) process is presented. In this work, the structural and EO properties of the solution-processed BaTiO3 film are characterized and its integration into an optical ring resonator is evaluated. The BaTiO3 film exhibits a fiber texture, has a large Pockels coefficient (r(eff)) of 139 pm V-1, and integration into a ring resonator-based modulator shows a V pi L of 1.881 V cm and a bandwidth of > 40 GHz. This enables low-cost, high-throughput, and flexible integration of BaTiO3 films on PIC platforms and the potential large-scale fabrication of nanophotonic BaTiO3 thin-film modulators.

Harnessing the full power of memristors as artificial synapses demands a simple and scalable crossbar architecture enabling their seamless integration into diverse applications. This Letter presents the 3×3 memristor crossbar array configuration featuring a grid of interconnected devices. The composition includes Al as the reactive top electrode connecting the device columns and Gd1−xCaxMnO3 (GCMO, x=0.8) serving as the bottom electrode connecting the device rows as well as the memristive material eliminating the need for additional layers and fabrication steps. Controlled-sized vias through insulating the Al2O3 layer connect the electrodes forming the active interface. The idea is validated with a test sample of 3×3 crossbars with the Au/GCMO/Al structure, Au enabling Ohmic contact to GCMO, with device resistive switching ratios mostly around 102 and yield of over 90%. The devised crossbar structure could provide a highly scalable, yet simple, geometry suitable for synaptic networks.

We conducted experiments involving BZO-added YBCO/Ca-doped YBCO heterostructures with varying layer numbers to investigate the role of Ca doping and the mechanism behind the enhanced J(c). Our findings reveal that the inclusion of Ca-doped layers enhances the quality of the YBCO matrix within the BZO-added layer by reducing microstrain and the formation of other crystalline defects, while also optimizing the oxygen content of YBCO with the increasing layer number. These structural improvements lead to a significant increase in self-field J(c)(0), which is also observed to correspond to an increase in in-field J(c)(B) without directly impacting flux pinning. The remarkable enhancement in J(c) at 65 K can be explained by a theoretical model, where the improvement in J(c) at high temperatures is attributed to the more coherent interface between the BZO nanorods and the YBCO matrix. Therefore, we conclude that the overall enhancement of J(c) in the Ca-doped heterostructures is attributed to the improved crystalline structure rather than enhanced flux pinning.

The present study systematically investigates the impact of strain-induced defects on the anisotropy of the critical current density across wide temperature and magnetic field ranges. We focus on 0-10 wt % BaZrO3 (BZO)-doped YBa2Cu3O7- x (YBCO) thin films that are deposited on SrTiO3 substrates with a 5 degrees surface miscut. Our findings highlight the crucial role played by these vicinal substrates in governing the growth of BZO nanorods within the YBCO films. Interestingly, we observe that the miscutinduced surface step-edge terraces serve as preferred nucleation sites for BZO, resulting in controlled nanorod growth and a significant enhancement in both the self-field and in-field critical current densities. Furthermore, we note that the optimal BZO content for effective flux pinning varies considerably depending on the applied temperature, magnetic field, and its orientation. These findings hold significant implications for the design and development of high-performance superconducting materials. The primary objective in such endeavors is to construct an optimal flux pinning structure that can achieve a high critical current density at relatively high magnetic fields.

Inspired by the biological nervous system, unsupervised spiking neural networks (SNNs) with the spike-timing-dependent plasticity (STDP) learning rule have been considered as the next-generation artificial neural networks (ANNs). However, to construct a functional SNN with high pattern recognition accuracy and low power consumption, hardware elements that present synaptic behavior still need to be developed. In this work, we studied Gd0.3Ca0.7MnO3 (GCMO)-based memristive devices comprised of an asymmetrical electrode configuration, Al/GCMO/Au. We verified its switching properties, focusing on single pulse switching and its usability as artificial synapse by means of the STDP learning rule. The dynamic range is well controlled by the pulse amplitude and width, and the conductance change shows a clear dependence on the interval between the pulses. Moreover, pattern recognition accuracy (>87%) is obtained in biologically plausible unsupervised SNN simulations when the device characteristics are utilized as the synaptic weight in the network. The results shed some light on the complexity of the operation of the devices for utilization in unsupervised SNNs, that is, the evolution of the ANNs for which the first proof-of-concept is currently being reported. Additionally, the bioplausibility of the simulated network opens the door to considering biohybrid systems and their enormous application possibilities.

The self out-of-plane oriented La 2 O 2 CO 3 thin film can be used as an integration tool to obtain fiber textured ferroelectric thin film stacks.