National Institute Of Materials Physics - Romania

In this study, we investigate the electrochemical performance and stability of silicon thin films, deposited by magnetron sputtering, as anodes for lithium-ion batteries (LIBs). The conventional direct current magnetron sputtering and the highly ionized technique high power impulse magnetron sputtering HiPIMS, known to produce high-density thin films, were used for the purpose. Silicon films with thicknesses of 50, 75, 124, 600 and 1000 nm were prepared and the morphology, density, and electrochemical performances of the films produced using both techniques were compared. Characterization of the prepared electrodes showed that the DCMSdeposited films exhibited lower density and large grain sizes, while the HiPIMS-deposited films exhibited higher density and relatively smaller grain sizes. The electrochemical tests revealed that the DCMS-deposited electrodes exhibited discharge capacities of 800 mAh g- 1 and 406 mAh g- 1 at a current density of 5 A g- 1 for electrode thicknesses of 600 nm and 1000 nm , respectively, demonstrating their high potential for fast charging applications. Additionally, these electrodes showed remarkable initial coulombic efficiency (ICE), with the 1000 nm thick electrode achieving an ICE of 96.08 %, outperforming traditional graphite anodes, which was attributed to a larger particle size and a lower SEI resistance. Furthermore, DCMS-deposited Si electrodes showed higher resistance to plastic deformation, which enhanced capacity retention and mitigated volume expansion, demonstrating their potential for high-performance anodes.

We report large-scale synthesis of monolayer WS2 films obtained by sulfurization of oxidized magnetron sputtered monolayer W precursors. Literature routes typically require similar to 800 degrees C, well above the 400 degrees C limit imposed by back-end-of-line (BEOL) integration. Here, using an enhanced chemical vapor deposition (CVD) approach, the magnetron sputtered ultrathin W precursor (a W monolayer film, 0.27 nm thick, which in ambient air becomes a WOx monolayer) is sulfurized at the lowest possible temperature (450 degrees C) within a microreactor, which consists of a sandwich-like structure formed by the precursor and a clean Si substrate. The obtained WS2 material has a good crystallinity and uniform morphology across the entire growth substrate, as confirmed by detailed characterization. These results highlight the versatility of the method combining magnetron sputtering and microreactor-CVD, facilitating its applications to wafer-scale synthesis of monolayer WS2, heterogeneously integrated into electronic circuits (a major objective for next-generation electronics and optoelectronics). Additionally, we investigate in detail the properties of WS2 films synthesized from a bilayer W precursor (0.43 nm thick), under the same conditions, and we calculated the frequencies of the second-order Raman scattering modes. For electrical measurements, we fabricated WS2/few-layer-graphene heterostructures, whose atomically clean interface yields reliable, low-resistance contacts. These devices exhibit resistive switching behavior, likely governed by vacancy migration, making it a promising candidate for memristive applications. Our results demonstrate that electronics-grade monolayer WS2 can be synthesized at 450 degrees C, approaching the BEOL requirement of 400 degrees C.

Design of products involves functional and sensory aspects, where surfaces play an important role. This study uses (i) sensory attributes to show that tactile sensation is highly dependent on surface roughness, and (ii) variation in pupil diameter to suggest that roughness close to fingerprint geometry causes less arousal. A panel of over 30 participants explored six plexiglass surfaces with different roughness generated by variations in milling speed and depth. The pattern obtained on the samples is periodic in one direction, with an average wavelength between 113 mu m to 600 mu m and an average height between 13 mu m and 123 mu m. During a blind touch, the sensory attributes of smoothness, grip and quality of each sample were evaluated by the panellists, as well as the emotional attributes of valence and arousal. The evolution of pupil diameter over time was also recorded, and its average value during the first two seconds of touch was considered as a new emotional attribute. These attributes made it possible to calculate six centred indicators, ranging between -1 and 1, for each panellist and each sample. Statistical analysis of these indicators showed that the declared valence is correlated with smoothness, grip, and quality, all gradually decreasing as roughness increases. These results will allow product designers to improve the hedonic experience of future users. To more precisely analyse arousal, valence, and the evolution of pupil diameter, three of the six samples, manufactured with the same cutting tool, were considered. Valence and arousal appeared relatively difficult to verbalised, but the pupil diameter allowed the samples to be discriminated. The sample with a roughness close to the geometry of the fingerprint appeared to be the least emotional.

Understanding the behavior of biomaterials under physiological conditions is essential for the development of new materials for implants and bone regeneration. This study addresses the critical need to evaluate how exposure to simulated body fluid (SBF) affects hydroxyapatite (HAp) and dextran-coated hydroxyapatite (HApDx) nanoparticles, which are widely considered for biomedical applications due to their bioactivity and biocompatibility. Structural, morphological, and surface property changes induced by SBF immersion were systematically investigated for the first time using advanced characterization techniques, such as X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), FT-Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and fractal and Minkowski functional analyses. The results revealed that SBF immersion significantly influenced both HAp and HApDx, leading to reduced crystallite sizes, surface smoothening, and enhanced structural homogeneity. FTIR and FT-Raman spectra indicated subtle structural modifications, while SEM and AFM analyses confirmed the formation of a biomimetic apatite layer and a decrease in surface roughness. These changes are indicative of improved bioactivity, suggesting enhanced potential for osteoconductivity and cellular interaction. Biological evaluations using MG63 osteoblast-like cells demonstrated favorable cell viability and adhesion across 24, 48, and 72 h, particularly for the samples immersed in SBF. AFM further confirmed that surface modifications supported the cell attachment and proliferation. Overall, our findings underscore the importance of SBF exposure in enhancing the physicochemical and biological performance of HAp-based materials, reinforcing their promise for biomedical applications.

The main objective of this research is to get a comprehensive view on the subsurface geological data on the Esh El Mellaha area and environs, Red Sea, Egypt. This includes determining the depth and structural characteristics of the basement surface beneath the region, as well as identifying additional gravity and magnetic sources and potential structures within the sedimentary cover. To achieve this goal, Bouguer gravity and aeromagnetic data were used, processed and analyzed. Various depth estimation techniques were employed to analyze subsurface structures, each offering distinct advantages. Euler Deconvolution effectively delineates structural discontinuities and fault systems, while the Source Parameter Imaging (SPI) method improves depth accuracy through wavenumber analysis. The Analytical Signal method enhances resolution, providing detailed depth variations. Across these methods, the estimated depth ranges from 300 to 5000 m, with an average depth of approximately 2380 m, offering critical insights into the subsurface geological framework. Two-dimensional (2.5D) modeling was conducted on two selected gravity and magnetic profiles to estimate the depth, dip, density, and magnetic susceptibility of the source bodies. Additionally, three-dimensional (3D) modeling was applied to Bouguer gravity and Reduced-to-the-Pole (RTP) magnetic profiles, providing a detailed representation of the causative source structures. The results of the 3D inversion of gravity and magnetic data reveal the subsurface distribution of density and magnetic susceptibility, aiding in the identification of major geological structures. The sectional maps and 3D models illustrate the vertical and horizontal variations in subsurface formations, highlighting distinct anomaly zones that may correspond to faults and lithological changes. The obtained results indicate that the sedimentary succession thickness is ranging from 1.0 to 2.2 km, a finding corroborated by the borehole data. Positive structural features identified in these models suggest promising targets for potential hydrocarbon reservoirs.

Ferroelectric-ferromagnetic heterostructures with well-defined polarization orientation are the focus of many research studies owing to their interesting interface-driven phenomena such as magnetoelectric coupling. In most practical electronic applications, capacitor geometry is often used, and in the case of ferroelectric-ferromagnetic heterostructures this can bring additional challenges regarding the overall functionality due to the physical phenomena from the ferroelectric-electrode interface. In this study, it is presented the influence of the top and bottom electrode on the electrical properties of Pb(Zr0,2Ti0,8)O3-La1-xSrxMnO3/SrTiO3(001) epitaxial heterostructures. This was done by growing the thin films with different layer stacking sequences by changing the Sr doping level from the bottom electrode. It was found that both the ferroelectric polarization orientation and tetragonality of the PZT films were significantly affected by the layer stacking sequence and Sr doping level of the bottom electrode. The ferroelectric polarization was oriented either towards or away from the Pb(Zr0,2Ti0,8)O3-La1-xSrxMnO3 interface depending on the layer stacking sequence, and the tetragonality increased when the Sr doping increases from x = 0.3 to x = 0.33. The materials used as the top electrode were Pt and Au/SrRuO3. Electric measurements performed in capacitor geometry show that the hysteresis curves start to be affected by leakage currents, which have a direct impact on the estimation of the ferroelectric polarization values and on the internal built in field. The most severely affected were the measurements performed with top Pt electrodes. The conduction mechanisms and leakage current values obtained by using the top Au/SrRuO3 electrode were found to be dependent on the Sr doping level, despite the fact that the electrical resistivity values and microstructures of the individual La1-xSrxMnO3 films were similar.

We propose an algorithm for determining the zeros of the electric conductivity in large molecular nanonstructures such as graphene sheets. To this end, we employ the inverse graph method, whereby non-zeros of the Green's functions are represented graphically by a segment connecting two atomic sites, to visually signal the existence of a conductance zero as a line that is missing. In rectangular graphene structures the topological properties of the inverse graph determine the existence of two types of Green's function zeros that correspond to absolute conductance cancellations with distinct behavior in the presence of external disorder. We discuss these findings and their potential applications in some particular cases.

This study presents a systematic approach to engineering the electron transport layer (ETL) in perovskite solar cells using a spray deposition technique to fabricate sequentially compact and mesoporous titanium dioxide (c-TiO2, m-TiO2) films. The spray coating method leads to the development of a distinct reticulated morphology characterized by well-defined wavy-like surface features and significantly increased roughness-at least twice that of spin-coated mesoporous films. The increased interfacial area between the mesoporous TiO2 and the perovskite layer facilitates more efficient charge transfer, contributing to higher device performance. By optimizing the deposition parameters, particularly the number of spray cycles for the m-TiO2 layer, we achieve a significant enhancement in device performance, with improvements in power conversion efficiency (PCE), reduced series resistance, and minimized hysteresis. Our results demonstrate that an optimal film thickness promotes better perovskite anchoring, while excessive deposition impedes light transmission and increases sheet resistance. These findings advance the practical fabrication of high-performance perovskite solar cells using simple solution-processing techniques and highlights the potential of scalable spray deposition methods for industrial-scale fabrication.

Ag-decorated TiO2 aerogels were synthesized using an acid-catalyzed sol-gel method, followed by drying under supercritical CO2 and annealing within the temperature range of 350-500 degrees C, with 50 degrees C increments. This study explores the preparation-structure-performance relationships of Ag-TiO2 aerogels influenced by the annealing process, focusing on their morphological, (micro)structural, optical, and textural properties and surface defects concerning photocatalytic activity. X-ray diffraction (XRD) and Raman spectroscopy confirmed that all aerogels exhibited a single anatase phase of TiO2, while electron microscopy (SEM/TEM) and XPS analysis demonstrated the presence of components. Increasing the annealing temperature resulted in particle size and pore structure changes, reducing the aerogel's overall surface area and porosity, as observed by SEM and nitrogen (N2) sorption analysis. Additionally, according to the Williamson-Hall (W-H) analysis based on the X-ray peak profile, the lattice microstrain value decreased while the crystallite size increased with rising annealing temperature. Optical investigation showed a strong UV light absorption characteristic of TiO2 and a visible light absorption band attributed to the plasmonic effect of silver nanoparticles. Moreover, a gradual photoluminescence (PL) quenching trend was observed with decreasing annealing temperature, indicating a reduction in the recombination rate of photo-induced electrons and holes in Ag-TiO2, alongside the formation of oxygen vacancies and structural defects, consistent with electron paramagnetic resonance (EPR) measurements. The Ag-decorated TiO2 aerogels demonstrated enhanced visible-light photocatalytic activity for methylene blue (MB) degradation, with the Ag-TiO2 aerogel annealed at 500 degrees C exhibiting the highest photocatalytic performance. This improvement can be attributed to the synergistic effects of chemical composition, plasmonic enhancement, morphological properties, and light absorption characteristics.

This study investigates the development of electrochemical genosensors using gold-coated electrospun polymeric fibers electrodes, Au/PMMA/PET and immobilized phosphorothioated oligonucleotides. Scanning electron microscopy (SEM) with energy-dispersive X-rays spectroscopy (EDS) revealed a uniform distribution of oligonucleotides on the fibers, contrary to planar gold electrodes Au/Ti/SiO2/Si, where network-like films were observed. X-ray photoelectron spectroscopy (XPS) confirmed the successful immobilization of the phosphorothioated oligonucleotides via strong covalent gold-sulfur bonds, while surface plasmon resonance (SPR) indicated superior binding affinity, with significantly lower equilibrium dissociation constants, when compared to unmodified probes. The detection of BCR/ABL fusion gene of chronic myeloid leukemia using differential pulse voltammetry and methylene blue as electroactive indicator, showed that the Au/PMMA/PET electrodes achieved a sensitivity of 379 +/- 12 mu A cm(-)(2) pM(-)(1) and a limit of detection of similar to 5.00 +/- 0.01 fM, outperforming the Au/Ti/SiO2/Si planar electrodes. Reduced non-specific adsorption was observed on the Au/PMMA/PET electrodes and attributed to the inherent charges introduced during the electrospinning process, which created localized electrostatic fields that repelled weakly adsorbing molecules. These findings demonstrate the potential of Au/PMMA/PET electrodes as a robust platform for further development of high-performance clinical diagnostic devices.