Chromium-based coatings are of interest for applications in harsh environments due to their high hardness and excellent resistance to corrosion. However, coatings deposited by magnetron sputtering often exhibit columnar microstructure which can compromise their performance by promoting porosity and reducing mechanical integrity. In this work, we present an approach to overcome this limitation by alloying Cr with Nb and N, forming (Cr1-xNbx)N-y films. Increasing Nb content in Cr1-xNbx films (0.19 <= x <= 0.55) led to an X-ray amorphous microstructure, confirmed by X-ray diffractometry and high-resolution transmission electron microscopy, while hardness remains similar to 8 to 11 GPa regardless of Nb content. Adding N to Nb-containing films (0.19 < x < 0.55) produced a nanocrystalline, denser microstructure with reduced column width, resulting in a similar to 66 % higher hardness (similar to 15 GPa) than the metallic films. Electrochemical measurements show enhanced passivity of Nb-containing coatings above 1 V vs. Ag/AgCl, attributed to the suppression of soluble Cr6+ species. X-ray photoelectron spectroscopy results indicate that Nb2O5 could oxidize soluble species in the electrolyte forming NbO2 on the surface. These findings show how Nb and N additions can tailor the microstructure, mechanical properties, and corrosion resistance of (Cr1-xNbx)N-y films.

Electrocatalytic CO 2 reduction (CO 2 RR) into value‐added chemicals represents a promising strategy for sustainable CO 2 utilization. This strategy relies on nanoscale structural engineering to gain desired CO 2 RR catalyst performance, which is insufficiently understood. For example, how the pore structure, defect distribution, and surface reconstruction can be used to promote catalytic activity and material stability is not clarified. Here, we investigate how mesopores and oxygen vacancies (V O ) synergistically regulate the CO 2 RR behavior of SnO 2 . Mesoporous SnO 2 (M‐SnO 2 ) synthesized hydrothermally shows enhanced mesoporosity and a higher specific surface area (59 vs. 21 m 2 g −1 ) than bulk SnO 2 (B‐SnO 2 ), achieving a Faradaic efficiency (FE) of 50.9% for formate at –1.15 V vs. reversible hydrogen electrode (RHE) and improved durability (FE loss: 13.0% vs. 55.8% after 12 h). Electrochemical analysis, in situ spectroscopy, and density functional theory (DFT) calculations reveal that mesostructure facilitates CO 2 adsorption, charge transfer, stabilizes *OCHO intermediates, and lowers the reaction energy barrier via V O in M‐SnO 2 . In addition, it is shown that mesostructure promotes formation of V O , which stabilizes the oxidation state of Sn and contributes to improved stability of the catalyst. These findings establish the synergistic roles of mesoporous structure and V O for optimizing Sn‐based CO 2 RR catalysts and offer guidance for rational design of efficient CO 2 RR electrocatalysts.

The deposition of dense, smooth, and columnar-free transition metal nitride films by reactive magnetron sputtering requires precise control of nitrogen content and substrate bias to optimize microstructure, and mechanical properties. In this work, the influence of ion bombardment on the composition, phase formation, and mechanical properties of CrNy and Cr1-xNbxNy films was investigated. Ion energies were controlled by varying the substrate bias from floating potential to -50, -75, and -100 V. CrNy films were deposited by DC magnetron sputtering (DCMS) with DC substrate biasing, while Cr1-xNbxNy films were grown using a hybrid high-power impulse magnetron sputtering Nb-HiPIMS-Nb/Cr-DCMS process with synchronized pulsed biasing (-50, -75, and -100 V). Nitrogen flow ratios of 5%, 7%, and 9%, were used, with the same substrate bias applied for each flow. Increasing nitrogen content promoted the formation of nitrogen-doped bcc-Cr and h-Cr2N phases, in DCMS-grown CrNy films. Increasing substrate bias improved the film density and indentation hardness from ~10-12 GPa to ~18-20 GPa, while the microstructure evolved from columnar to dense and columnar-free. In hybrid Nb-HiPIMS/Cr-DCMS grown Cr1-xNbxNy films, Nb incorporation enhanced nitrogen uptake compared with DCMS-CrNy. Columnar-free microstructures were obtained at 0.20 ≤ y ≤ 0.30, whereas higher nitrogen contents led to the formation of Nb containing h-Cr2N and columnar growth. Hardness remained at ~14-16 GPa regardless of bombarding Nb+ ion energy. These results demonstrate that nitrogen concentration is a key parameter that governs microstructural evolution in CrN-based systems, while Nb incorporation modifies nitrogen uptake and the processing window for achieving dense, columnar-free films.

Electrocatalytic CO2 reduction (CO2RR) into value-added chemicals represents a promising strategy for sustainable CO2 utilization. This strategy relies on nanoscale structural engineering to gain desired CO2RR catalyst performance, which is insufficiently understood. For example, how the pore structure, defect distribution, and surface reconstruction can be used to promote catalytic activity and material stability is not clarified. Here, we investigate how mesopores and oxygen vacancies (VO) synergistically regulate the CO2RR behavior of SnO2. Mesoporous SnO2 (M-SnO2) synthesized hydrothermally shows enhanced mesoporosity and a higher specific surface area (59 vs. 21 m2 g-1) than bulk SnO2 (B-SnO2), achieving a Faradaic efficiency (FE) of 50.9% for formate at -1.15 V vs. reversible hydrogen electrode (RHE) and improved durability (FE loss: 13.0% vs. 55.8% after 12 h). Electrochemical analysis, in situ spectroscopy, and density functional theory (DFT) calculations reveal that mesostructure facilitates CO2 adsorption, charge transfer, stabilizes *OCHO intermediates, and lowers the reaction energy barrier via VO in M-SnO2. In addition, it is shown that mesostructure promotes formation of VO, which stabilizes the oxidation state of Sn and contributes to improved stability of the catalyst. These findings establish the synergistic roles of mesoporous structure and VO for optimizing Sn-based CO2RR catalysts and offer guidance for rational design of efficient CO2RR electrocatalysts.

Epitaxial growth of AlN on silicon is highly attractive for integrated nitride-based devices but remains challenging, as conventional techniques typically require high growth temperatures or suffer from limited industrial scalability. High-power impulse magnetron sputtering (HiPIMS) has emerged as a promising alternative by enabling enhanced ionization of the sputtered species and control of ion energy through substrate biasing. However, selective acceleration of the ionized film-forming species in HiPIMS is particularly challenging for AlN, due to the low atomic mass of Al relative to Ar. In this work, we successfully demonstrate that selective Al+ ion acceleration can be achieved by tuning the HiPIMS pulse length to exploit gas rarefaction, which suppresses Ar+ ion generation while sustaining a high Al+ ion density. Time-resolved mass spectrometry, supported by process modeling, reveals that increasing the pulse length induces a pronounced temporal separation between Ar+ and Al+ ion fluxes, resulting in a metal-ion–rich time window suitable for synchronized substrate biasing. Under these conditions, epitaxial AlN growth on Si(111) is achieved at a substantially reduced substrate temperature without the use of buffer or seed layers. The resulting films exhibit a clear enhancement in crystalline quality, strain state, and surface morphology consistent with a shift from Ar-ion–dominated to metal-ion–assisted growth. These findings establish pulse-length–controlled HiPIMS as an effective strategy for metal-ion–assisted epitaxial growth of AlN on silicon at moderate temperatures.

High quality epilayers with a minimum of microstructural features can act as test beds to elucidate intrinsic materials properties and improve the understanding of more complex materials. We report on the growth of epitaxial Ti1-xAlxNy thin films with low aluminium content (x = 0–0.4) on MgO (001) substrates using reactive magnetron co-sputtering from a pure Ti and a compound Ti0.75Al0.25 target. The films are fully strained and display a pronounced (001) orientation with low mosaicity and high lateral coherence. The hardness increases up to 29 GPa because of solid-solution hardening and coherency strains associated with early-stage spinodal decomposition, despite an increase in tensile residual stress with Al content. Electrical resistivity increases as the charge carrier concentration decreases with Al content, because enhanced solute scattering and progressive depletion of the metallic Ti-3d-N-2p hybridized conduction band. Al substitution for Ti introduces lattice distortions that increase disorder, reflected by a decreasing Ioffe-Regel parameter (kFl) with Al content. Mobility shows a non-monotonic trend, first decreasing and then increasing with Al content. The changes in electrical resistivity, carrier density, mobility and Ioffe–Regel parameter imply a shift from metallic to increasingly localized electronic transport with increasing Al incorporation.

This study investigates magnetic domains in Fe/Si and Fe/Si + B4C multilayers using spin flip off-specular polarized neutron reflectometry. The results show that Fe/Si multilayers exhibit pronounced spin flip off-specular scattering originating from magnetic domains that are uncorrelated out of plane. With increasing external magnetic field the domains progressively coalesce and their magnetization rotates toward alignment with the applied field, approaching a homogeneous magnetic state at higher fields. In contrast, Fe/Si + B4C multilayers exhibit no detectable spin flip off-specular scattering already at low fields, indicating that the multilayer reaches magnetic saturation at significantly lower applied fields. The scattering patterns are interpreted using distorted wave Born approximation simulations in BornAgain, enabled by our added code for simulating magnetic domains and magnetic ordering. To further probe the magnetic behavior, low-energy mu+SR measurements were performed, representing the first mu+SR investigation of polarizing neutron optics multilayers. Together with comparison to previously reported VSM data, these measurements provide insight into the magnetic behavior across short range, medium range, and long range length scales. The results show that incorporating approximately 15 vol.

Neutron reflectivity is a powerful technique for probing density profiles in films, with applications across Physics, Chemistry, and Biology. However, challenges arise when dealing with samples characterized by high roughness, unknown scattering length density (SLD) with low contrast, very thin layers, or complex multi-layered structures, that cannot be uniquely resolved due to the phase problem. Incorporating a magnetic reference layer (MRL) and using polarized neutron reflectivity improves sensitivity and modeling accuracy by providing complementary information. In this study, we introduce a quantitative way to compare MRL systems in a model-free way. We apply this approach to demonstrate that CoTi alloys offer a superior solution as an MRL compared to the commonly used Fe or Ni-based MRLs. The low nuclear and magnetic scattering length densities of CoTi significantly enhance sensitivity, making it particularly advantageous for soft matter research. Furthermore, the tunable Co vs Ti ratio allows for optimization of the SLDs to achieve maximum sensitivity, establishing CoTi as a highly effective choice for MRL applications. The applied simulation framework for optimizing MRL sensitivity to a specific materials system and research question is a generic approach that can be used prior to growing the MRL for a given experiment.

This study further investigates the effects of 11B4C co-sputtering on the structural and optical properties of Fe/Si stacked multilayers, with a focus on neutron supermirror applications. X-ray and neutron reflectivity techniques confirm with greater clarity that 11B4C incorporation improves interface sharpness, reduces roughness, and enhances reflectivity for various multilayer periods, compared to earlier studies on a single period thickness. Neutron reflectivity measurements show reduced spin-flip intensities, while wafer-curvature measurements indicate a 50 % reduction in internal stress, allowing for higher mechanical stability of the multilayers. These improvements are attributed to the amorphization of Fe layers, which also suppress the formation of structural and magnetic domains responsible for stress and spin-flip scattering. In contrast, the pure Fe/Si sample exhibits a persistent half-order Bragg peak, indicating residual antiferromagnetic coupling. The results demonstrate that 11B4C enhances neutron optics by reducing spin-flip effects, increasing reflectivity and polarization, and alleviating stress, enabling the use of polarizers at reduced external fields compared to pure Fe/Si multilayers. These findings establish 11B4C as a transformative material for advancing neutron supermirror technology, paving the way for more efficient, stable, and high-performance polarizers in next-generation neutron optics.

This study investigates the effects of incorporating 11B4C interlayers into Fe/Si multilayers, with a focus on interface quality, reflectivity, polarization, and magnetic properties for polarizing neutron optics. It is found that the introduction of 1-2 & Aring; 11B4C interlayers significantly improves the interface sharpness, reducing interface width and preventing excessive Si diffusion into the Fe layers. X-ray reflectivity and polarized neutron reflectivity measurements show enhanced reflectivity and polarization, with a notable increase in polarization for 30 & Aring; period multilayers. The inclusion of interlayers also helps prevent the formation of iron-silicides, improving both the magnetic properties and neutron optical performance. However, the impact of interlayers is less pronounced in thicker-period multilayers (100 & Aring;), primarily due to the ratio between layer and interface widths. These results suggest that 11B4C interlayers offer a promising route for optimizing Fe/Si multilayer performance in polarizing neutron mirrors.

Magnetic hysteresis properties in Fe/Si multilayers have been studied as a function of the B4C content to control magnetization amplitude, coercivity, and hysteresis tilt, properties that are beneficial to tune for advancing applications in e.g. data storage, spintronics, and sensors. With an ion-assisted magnetron sputtering technique, 35 distinct thin film multilayer samples were prepared and their magnetic and structural properties were characterized by vibrating sample magnetometry, X-ray photoelectron spectroscopy, near edge X-ray absorption fine structure spectroscopy, and X-ray and neutron scattering methods. Key findings indicate that adding B4C lowers the coercivity and can decrease the saturation magnetization, demonstrating the tunability of magnetic responses based on composition. For samples with Lambda=30 & Aring; periodicity, 10-15 % of B4C addition produces antiferromagnetically (AF) coupled multilayers, and such AF coupling strength increases with the B4C content. Our findings reveal that B atoms do not chemically bind within the Fe atoms but instead occupy interstitial positions, disrupting medium- to long-range crystallinity thereby inducing the amorphization. Thereon, the observed effects on magnetic properties are directly attributed to this amorphization process caused by the presence of B4C. The demonstrated ability to finely adjust magnetic properties by varying the B4C content offers a promising approach to overcome challenges in magnetic device performance and efficiency.

Artificial superlattices exhibit exceptional electronic, magnetic, optical, and mechanical properties which make them unique candidates for applications in a broad range of technologies. A common key feature of superlattices is the need for atomically abrupt interfaces. However, superlattices comprised of materials with different properties, such as melting points and diffusivities, pose large challenges for achieving high crystal quality of both constituents with abrupt interfaces. By employing ion-assisted magnetron sputter epitaxy, we present an innovative solution to this problem with utilizing a unique combination of thermal radiation and kinetic energy that enable sufficient adatom mobility for epitaxial growth of both materials. The research was implemented for the case of CrB2/TiB2 heteroepitaxial superlattices, as neutron interference mirrors, wherein the constituents' melting points differ by 1100 K. Ion-induced intermixing was avoided by commencing growth of each TiB2 and CrB2 layer by up to 3 unit cells (uc) without ion assistance, forming a buffer to protect the interface during the ion-assisted growth of the remainder of each layer. Heteroepitaxial superlattice growth with interface widths sigma(CrB2) similar to 1 uc and sigma(TiB2) similar to 2 uc was confirmed for different modulation periods. More than 3000 uc (similar to 1 mu m) thick superlattices with abrupt interfaces were demonstrated for neutron mirror applications.

From nanoscale devices including sensors, electronics, or biocompatible coatings to macroscale structural, automotive or aerospace components, fundamental understanding of plasticity and fracture can guide the realization of materials that ensure safe and durable performance. Identifying the role of atomic-scale plasticity is crucial, especially for applications relying on brittle ceramics. Here, stress-intensity-controlled atomistic simulations of fracture in cubic Ti1-xAlxN model systems demonstrate how & Aring;-scale plasticity - manifested as lattice distortions, phase transformation, nucleation and emission of dislocations - substantially affects the macroscale fracture toughness (K-Ic) and fracture strength (sigma(f)) of brittle ceramics. The extent of plastic deformation in Ti1-xAlxN increases monotonically with the Al content (x), due to a corresponding decrease in cubic -> hexagonal polymorph transition energies and unstable stacking fault energies. Overall, plasticity positively affects the mechanical properties, resulting in optimal combinations of strength and toughness for x approximate to 0.6. However, for x exceeding similar to 0.7, the benefits of plasticity diminish. The initial rise followed by a decline in K-Ic(x) and sigma(f)(x) is explained based on the interplay between phase transformation, shear-induced faulting, and tensile cleavage on the easiest fracture plane. The results highlight the impact of atomic-scale plasticity on observable properties and point to strategies for toughening ceramics through control of polymorph competition.

Typical length scales associated with superconductivity are in the range of nanometers. Accordingly, measurements of electrical resistance over much larger distances are supposed to be insensitive to details of spatial inhomogeneities of superconducting order. We observe that current paths adopt a highly nonuniform distribution at the onset of the superconducting transition which is manifested in the development of a finite transverse resistance. The anisotropic distribution of current density indicates the emergence of electronic inhomogeneities perceivable over macroscopic distances, characterized by a length scale which is unrelated to the structural properties of the superconducting films. Our experiments reveal the ubiquitous nature of this phenomenon in conventional superconductors.

Mesoporous silica materials are promising carriers for antimicrobial peptides (AMPs), offering a versatile platform for combating bacterial infections. However, achieving high loading efficiency and controlled AMP release under physiological conditions remains a challenge. This study introduces a protein-capped mesoporous silica-based delivery system for treating topical bacterial infections. The system leverages elevated protease activity at infection sites to trigger the release of the sequence-optimized antimicrobial lipopeptide L-6-C5 (SOAP), facilitating efficient bacterial killing. SOAP was loaded into aminopropyl-functionalized SBA-15 mesoporous silica (amino-SBA-15) and capped with bovine serum albumin (BSA) or casein, forming amino-SBA-15-SOAP@protein. Protein adsorption prevented premature SOAP release while enabling protease-triggered delivery. BSA capping achieved 92.6 ± 0.2 % loading efficiency and enhanced peptide retention by 4.5-fold compared to non-capped particles, while casein yielded only a 1.25-fold increase. In the absence of proteases, SOAP release followed first-order kinetics, resulting in sustained release over 6 days. When exposed to trypsin, the release mechanism changed from diffusion-based to anomalous non-Fickian transport with zero-order kinetics, enabling rapid and efficient SOAP release. Proteolytic degradation of the protein cap also accelerated particle degradation and aggregation, offering insights into release dynamics under physiological conditions. The BSA-capped systems (amino-SBA-15-SOAP@BSA) showed effective bacteriostatic activity against Staphylococcus aureus (S. aureus), low hemolytic activity, and high cytocompatibility toward human dermal fibroblasts, outperforming free SOAP. Additionally, BSA capping reduced nonspecific protein binding in serum-rich media. By integrating sustained SOAP delivery with protease-triggered release, the amino-SBA-15-SOAP@BSA system addresses key limitations in AMP delivery, providing a promising strategy for controlled and localized AMP delivery in the treatment of topical bacterial infections.

The strength of refractory ceramics is much limited by their brittleness. Counterintuitively, we observe simultaneous high hardness and metallic-like ductility in highly overstoichiometric single-crystal HfN1.22 and HfN1.33 films grown by ion-assisted reactive magnetron sputtering. Electron microscopy, diffraction methods, and ab-initio calculations reveal the existence of a novel type of superstructure ordering of both metal vacancies and nitrogen interstitials into sub-nanometer hyper-overstoichiometric and quasi-stoichiometric domains that self-organize into a checkerboard pattern superimposed onto the NaCl-structured lattice. A high intrinsic dislocation density enables an unparallelled ductility and strain hardening in room temperature uniaxial compression of HfN1.22 micropillars, by activation of {111}<011> slip. The films simultaneously exhibit a high hardness – tunable up to 28 GPa via control of stoichiometry – and a remarkable fracture resistance due to dislocation-mediated stress dissipation. The presented findings provide a route for synthesizing nitride superstructured films with unique hardness/toughness combinations.

Sputter-deposited titanium diborides are promising candidates for protective coatings in harsh and extreme conditions. However, growing these layers from TiB2 diboride targets by DC magnetron sputtering usually leads to over-stoichiometric layers with low crystal qualities. Moreover, superlattices with TiB2 as one of the constituents have been becoming popular, owing to their superior mechanical properties compared to single layer constituents in addition to their use in other applications such as neutron optics. Here, we propose the use of a TiB (Ti:B = 1:1) sputtering target in an on-axis deposition geometry and demonstrate the growth of epitaxial substoichiometric TiB1.8 thin films. Furthermore, we present the growth of CrB1.7/TiB1.8 superlattices, from TiB (Ti: B = 1:1) and stoichiometric CrB2 targets, with abrupt interfaces as promising materials system for neutron interference mirrors. The high crystal quality structure with well-defined interfaces is the common feature of superlattices which, regardless of application, should be addressed during the growth process. Utilizing TiB target, all films crystallize in the hexagonal AlB2 structure. The sub-stoichiometry of the TiB1.8 films was accompanied by the presence of planar defects embedded in the films. CrB1.7/TiB1.8 superlattices exhibited a homogeneous boron distribution within the layers with no sign of B-rich tissue phases through the layers. This study demonstrates the feasibility for TiB as sputter target material, that offers a solution for deposition of TiB2-based superlattices without the need to adjust the deposition parameters. Such adjustments would otherwise be unavoidable for tuning the TiB2 composition and could affect the growth of the other constituent materials.

State-of-the-art Ni/Ti supermirror neutron optics have limited reflected intensity and a restricted neutron energy range due to the interface width. Incorporating low-neutron-absorbing 11B4C enhances reflectivity and allows for thinner layers to be deposited, with which more efficient supermirrors with higher m-values can be realized. However, incorporating 11B4C reduces the optical contrast, limiting the attainable reflectivity at low scattering vectors, making this approach infeasible. This study explores various approaches to optimize the material design of 11B4C-containing Ni/Ti supermirrors to maintain high reflectivity at low scattering vectors and achieve low interface widths at large scattering vectors. The scattering length density contrast versus interface width is investigated for multilayer periods of 30 Å, 48 Å, and 84 Å, for designs involving pure Ni/Ti multilayers, multilayers with 11B4C co-deposited in Ni and Ti layers, multilayers with 11B4C co-deposited only in Ni layers, and multilayers with 11B4C as thin interlayers between Ni and Ti layers. Our results suggest that a depth-graded hybrid material design by incorporating 11B4C inside the Ni and Ti layers, below approximately 26 Å, and introducing 1.5 Å 11B4C interlayers between the thicker Ni and Ti layers can achieve a higher reflectivity than state-of-the-art Ni/Ti multilayers over the entire scattering vector range.

We report on phase and strain changes in Ti1-xAlxN (0 <= x <= 0.61) coatings on cutting tools during turning recorded in operando by high-energy x-ray diffractometry. Orthogonal cutting of AISI 4140 steel was performed with cutting speeds of 360-370 m/min. Four positions along the tool rake face were investigated as a function of time in cut. Formation of gamma-Fe in the chip reveals that the temperature exceeds 727 degrees C between the tool edge and the middle of the contact area when the feed rate is 0.06 mm/rev. Spinodal decomposition and formation of wurtzite AlN occurs at the positions of the tool with the highest temperature for the x >= 0.48 coatings. The strain evolution in the chip reveals that the mechanical stress is largest closest to the tool edge and that it decreases with time in cut for all analyzed positions on the rake face. The strain evolution in the coating varies between coatings and position on the rake face of the tool and is affected by thermal stress as well as the applied mechanical stress. Amongst others, the strain evolution is influenced by defect annihilation and, for the coatings with highest Al-content (x >= 0.48), phase changes.

Single-crystal CrB2/TiB2 diboride superlattices with well-defined layers are promising candidates for neutron optics. However, excess B in sputter-deposited TiBy using a single TiB2 target deteriorates the structural quality of CrBx/TiBy (0001) superlattices. We study the influence of co-sputtering of TiB2 + Ti on the stoichiometry and crystalline quality of 300-nm-thick TiBy single layers and CrBx/TiBy (0001) superlattices on Al2O3(0001) substrates grown by DC magnetron sputter epitaxy at growth-temperatures T-S ranging from 600 to 900 degree celsius. By controlling the relative applied powers to the TiB2 and Ti magnetrons, y could be reduced from 3.3 to 0.9. TiB2.3 grown at 750 degree celsius exhibited epitaxial domains about 10x larger than non-co-sputtered films. Close-to-stoichiometry CrB1.7/TiB2.3 superlattices with modulation periods Lambda = 6 nm grown at 750 degree celsius showed the highest single crystal quality and best layer definition. TiB2.3 layers display rough top interfaces indicating kinetically limited growth while CrB1.7 forms flat and abrupt top interfaces indicating epitaxial growth with high adatom mobility.