GISAXS Research Articles

Molecular Design and Alignment for Ambipolar SCLC Mobility in Self-Assembled Columnar Discogens.

The future of next-generation electronics relies on low-cost organic semiconductors that are tailored to simultaneously provide all requisite optoelectronic properties, focusing greatly on ambipolar charge-transport and solution processability. In this regard, room-temperature discotic liquid crystals (DLCs) are potential candidates, where quasi-1D self-assembly affords a charge-transport channel along their columnar axis. This work shows a molecular design strategy by utilizing anthraquinone as the primary motif, surrounded by ester functionalized tri-alkoxy phenyl units to develop room-temperature DLCs (1.1-1.3). Here, the polar ester functionality stabilizes the columnar mesophase over a wide range through the involvement of dipole-dipole interaction along with the π-π stacking. Throughout the entire mesophase transition, reported compounds 1.1-1.3 exhibit a highly ordered 2D columnar oblique (Colob) self-assembly. Space charge limited current (SCLC) experiments reveal balanced ambipolar charge transport, with the maximum hole and electron mobilities of 5.04 and 4.93 cm2 V-1 s-1, respectively. From the conoscopic results, their propensity to align in a highly homeotropic fashion is demonstrated. It is further justified by the azimuthal plot corresponding to the (11) peak of grazing incidence small angle X-ray scattering (GISAXS), denoting the crucial role of the design and alignment for efficient movement of charge carriers in the material.

Annealing Process-Induced Microstructural Variation in NiV/B4C Multilayers

The annealing process is one of the most common methods used to study the thermal stability of multilayers. To study the effect of the annealing process on the microstructural variation in NiV/B4C multilayers, different annealing experiments were performed on NiV/B4C multilayers with a d-spacing of 8 nm. This work provides a foundation for the fabrication of non-periodic NiV/B4C multilayers. The NiV/B4C multilayers were investigated by grazing-incidence X-ray reflectometry (GIXR), X-ray diffuse scattering (XRS), atomic force microscopy (AFM), X-ray diffraction (XRD), grazing-incidence small-angle X-ray scattering (GISAXS) and transmission electron microscopy (TEM). The temperature-dependent experiments showed that annealing at 70–290 °C slightly increased the period thickness and interface width. Annealing at higher temperatures resulted in significant structural changes and thickness ratio (Г = dNiV/d) changes from 0.4 to 1/3 at 340 °C. The time-dependent results showed that the microstructural variations primarily occurred after 60 min. The XRD, XRS, GISAXS and TEM were further used to study microstructural changes. It was found that the NiV/B4C multilayers exhibited a microcrystal structure after annealing, and that enhanced crystallinity and an increase in interface roughness were the main reasons for the microstructural changes.

Nano- and Mesoporous Structure Formation Probed with in Situ/in Operando Small and Wide-Angle X-Ray Scattering Analysis during Electrodeposition and Dealloying Processes

Electrochemical formation of nanoporous materials by electrodeposition or dealloying is essential in various fields such as catalysis, energy storage, and sensing due to their high surface areas and controlled pore sizes. Understanding the underlying principles leading to specific morphologies during the electrochemical protocol is of importance for a directed design of desired morphologies. In situ/in operando analysis at the nanoscale, such as grazing incidence small and wide angle X-ray scattering (GISWAXS), is an important tool to understand the pathway of the structure evolution at both the mesostructural and the crystalline levels. Here the development of a versatile electrochemical cell for GISWAXS [1] was essential to be able to investigate such processes.In this presentation an overview of various projects utilizing GISWAXS is given: (i) dealloying of the binary systems AgAu and CoPd [2]; electrodeposition of (ii) vertical aligned hexagonal Pt films using liquid crystal templating with Brij®56 [3]; and (iii) mesoporous platinum nickel films using Pluronic P123 as structure directing agent, as proposed by [4]. Additionally, some current highlights in the field of electrodeposition of ordered materials will be presented. M. Bogar, I. Khalakhan, A. Gambitta, Y. Yakovlev, H. Amenitsch, In situ electrochemical grazing incidence small angle X-ray scattering: From the design of an electrochemical cell to an exemplary study of fuel cell catalyst degradation. J. Power Sources. 477, 229030 (2020). Gößler, E. Hengge, M. Bogar, M. Albu, D. Knez, H. Amenitsch, R. Würschum, In Situ Study of Nanoporosity Evolution during Dealloying AgAu and CoPd by Grazing-Incidence Small-Angle X-ray Scattering. J. Phys. Chem. C. 126, 4037–4047 (2022). P.A. Wieser, D. Moser, B. Gollas., H. Amenitsch, Monitoring of Pore Orientation by in Operando Grazing Incidence Small-Angle X-ray Scattering during Templated Electrodeposition of Mesoporous Pt Films, Acs Appl. Materials and Interfieces 15, 47604-47614 (2023). K. Eiler, S. Surinach, J. Sort, E. Pellicer, Mesoporous Ni-rich Ni–Pt thin films: Electrodeposition, characterization and performance toward hydrogen evolution reaction in acidic media, Applied Catalysis B, Environmental 265, 118597 (2020). Fig. 1 (a) Scheme of the experimental setup for monitoring electrodeposition of mesoporous PtNi via in operando GISWAXS. The incoming X-ray beam impinges on the sample at a glancing angle αi (shown in the zoomed inset into the electrochemical cell). The scattering intensity is recorded simultaneously by two detectors: one in the direct beam, to study the GISAXS pattern during electrodeposition, and the other in the GIWAXS regime to resolve the diffraction pattern. (b) Chronoamperometric data during electrodeposition, performed under constant potentials at - 0.7 V vs AgCl. (c) Exemplary SEM micrograph of resulting mesoporous PtNi film. Figure 1

Thermal evolution of helium bubbles in tungsten by GISAXS and TDS

Grazing-incidence small-angle x-ray scattering (GISAXS) and thermal desorption spectroscopy (TDS) were used to study the thermal evolution of helium (He) bubbles in tungsten (W). W samples were exposed to a low ion energy (∼20 eV, sheath accelerated) He plasma at two sample temperatures: 573 K (low-temperature) and 1050 K (high-temperature). They were then annealed to temperatures of 773 K, 873 K and 998 K. GISAXS analysis showed an increase in the median bubble radius of the high-temperature samples from 6.42 Å to 12.87 Å as a result of annealing to 998 K. No changes in the bubble radii distributions were observed for the low-temperature samples and the median radius remained at ∼4 Å even after annealing. TDS showed that the desorption behaviour of He in W has a dependence on the sample temperature during plasma irradiation. The higher-temperature sample experienced a maximum desorption rate that is an order of magnitude larger than the low-temperature sample. The desorption profile of the high-temperature sample spanned a wider temperature range, 500 K - 1500 K, than the low-temperature sample, 500 K - 750 K. The formation and thermal evolution of He bubbles in W have a clear dependence on sample temperature during plasma exposure. The differences in annealing behaviour observed in this work agree with prior in-situ TEM annealing experiments and help explain macroscopic plasma-material interaction effects such as recrystallisation suppression.

Grazing-incidence small-angle neutron scattering at high pressure (HP-GISANS): a soft matter feasibility study on grafted brush films

Grazing-incidence small-angle neutron scattering (GISANS) under pressure (HP-GISANS) at the solid (Si)–liquid (D2O) interface is demonstrated for the pressure-induced lateral morphological characterization of the nanostructure in thin (<100 nm) soft matter films. We demonstrate feasibility by investigating a hydrophobic {poly[(2,2,3,3,4,4,5,5-octafluoro)pentyl methacrylate]} (POFPMA)–hydrophilic {poly[2-(dimethylamino)ethyl methacrylate]} (PDMAEMA) brush mixture of strong incompatibility between the homopolymers, anchored on Si, at T = 45°C for two pressures, P = 1 bar and P = 800 bar. Our GISANS results reveal nanostructural rearrangements with increasing P, underlining P-induced effects in tethered polymer brush layers swollen with bulk solvent.

Nanostructure Formation in Glycerolipid Films during Enzymatic Hydrolysis: A GISAXS Study.

Responsive nanostructured films from food-grade lipids can be valuable for food, pharmaceutical, and biotechnological science. Lyotropic liquid crystalline structures that respond to enzymes in their environment can, for instance, be innovated as drug delivery platforms or biosensors. However, the structural changes that such films undergo during enzymatic reactions with lipase are not yet understood. This work demonstrates the preparation of mesostructured lipid films from the food-grade lipids glycerol monooleate (GMO) and triolein on silicon wafers and their digestion with pancreatic lipase using time-resolved synchrotron grazing incidence small-angle X-ray scattering (GISAXS). The film structure is compared with the corresponding GMO/triolein bulk phases in excess water. Increasing the GMO/triolein ratio in the film makes it possible to modulate the structure of the films from oil coatings to inverse hexagonal and inverse bicontinuous cubic films. Pancreatic lipase triggered swelling of the internal film nanostructure and eventually structural transformation inside the film. Orientation and reorientation of the internal film structure relative to the silicon wafer surface were observed during the preparation of the films and their digestion. The findings contribute to the understanding of self-assembly in thin films and guide the development of enzyme-responsive coatings for the functional modification of various substrates.

High-temperature furnace for in situ GISAXS studies

Abstract A high-temperature furnace was constructed to perform in situ Grazing-Incidence Small-Angle X-ray Scattering (GISAXS) experiments at high temperatures for isothermal studies. The furnace consists of two interconnected chambers: (i) a main chamber housing the heating elements, where the sample is inserted during GISAXS measurements, and (ii) a pre-chamber where the sample is maintained near room temperature until the temperature in the main chamber reaches the pre-selected value. The two-chamber design allows a rapid increase of the sample temperature and avoids the sample overheating, conditions desirable for studies of the formation and growth of nanoparticles under isothermal annealing. In a practical application, the furnace was used to investigate the kinetics of the formation of NiSi2 silicide nanocrystals endotaxially grown in Si(001) wafers. This experiment allowed us to gain insights into the growth process and evaluate the performance of the furnace for in situ GISAXS studies. The high-temperature furnace provides a robust tool for studying the effect of annealing temperature on the kinetics of the growth of nanoparticles in thermally activated processes with special advantages in studies in which isothermal conditions are required.

Macroscopic Monograin Nano-Gyroid Thin Films in 4-inch Scale Through Shear-Rolling and Subsequent Solvent Annealing.

The gyroid structure from self-assembly is highly attractive for optical applications such as photonic crystals and metamaterials. However, due to the direction-dependent nature of these applications, achieving a monograin-level structure over a large area has remained challenging. In this study, the fabrication of unidirectionally oriented anisotropic nanocylinders of polystyrene-block-polydimethylsiloxane (PS-b-PDMS) is reported block copolymer thin films up to a 4-inch scale via a shear-rolling process, followed by solvent annealing to induce phase transition to nearly monograin gyroid structures. Grazing-incidence small-angle X-ray scattering (GISAXS) analysis and cross-sectional scanning electron microscope (SEM) images in the direction parallel to the shear-rolling direction reveal the preferential orientation with the (111) plane onto the YZ axis of the film, while only the (110) plane on the YZ axis of the film is observed in the perpendicular direction, with grain sizes approaching single-grain levels. For metamaterial applications, the PDMS domain is selectively removed, and gold is electroplated to produce monograin gold gyroid films.

Morphology Optimization by Non-Halogenated and Twisted Volatile Solid Additive for High-Efficiency Organic Solar Cells.

Recently, volatile solid additives have attracted tremendous interest in the field of organic solar cells (OSCs), which can effectively improve device efficiency without sacrificing the reproducibility and stability of the device. However, the structure of reported solid additives is onefold and its working mechanism needs to be further investigated. Herein, a novel non-halogenated and twisted solid additive 1,4-diphenoxybenzene (DPB) is employed to optimize the morphology of the active layer in OSCs. The properties of additive DPB, morphology of active layer, and carrier dynamics behaviors have been systematically investigated through theoretical calculations, in situ and ex situ spectroscopy, grazing-incidence wide-angle X-ray scattering (GIWAXS), and grazing-incidence small-angle X-ray scattering (GISAXS) measurement, as well as ultrafast spectroscopy technology. The results reveal that the twisted additive DPB selectively interacts with acceptor Y6, and thus forms optimized morphology of active layer with increased molecular crystallinity, tight molecular packing, and favorable phase separation. As a result, the optimized devices deliver a remarkable power conversion efficiency (PCE) of 19.04%, which is the highest value for the D18-Cl:N3 system to date. These results demonstrate that non-halogenated and twisted solid additive DPB has broad prospects in the preparation of highly efficient OSCs, providing theoretical and experimental guidance for the development of high-performance solid additives.

Nanobubble Formation and Coverage during High Current Density Alkaline Water Electrolysis.

Gas bubbles are a necessary byproduct of water electrolysis whereby hydrogen and oxygen are produced from water. These attached gases reduce the electrode's active area, which necessitates a deep understanding of the bubble life cycle starting from nanobubbles. Synchronized with the electrochemistry, the time evolution of the surface nanobubble size and coverage is resolved using grazing incidence small-angle X-ray scattering (GISAXS) and correlated with optical microscopy and theoretical calculations to show that a significant portion of the surface is covered in nanobubbles after larger micron-sized bubbles are observed. These nanobubbles increase in number and decrease in size, toward 2 nm diameter, with the charge passed. The trend in size and number is consistent with an increase in supersaturation, which reduces the nascent bubble size. Altogether, this study suggests a significant portion of the surface contains nanobubbles and that strategies to reduce the dissolved hydrogen would be effective at reducing the nanobubble surface coverage.

Sputter-deposited TiOx thin film as a buried interface modification layer for efficient and stable perovskite solar cells

Despite perovskite solar cells (PSCs) based on a SnO2 hole-blocking layer (HBL) are achieving excellent performance, the non-perfect buried interface between the SnO2 HBL and the perovskite layer is still an obstacle in achieving further improvement in power conversion efficiency (PCE) and stability. The poor morphology with numerous defects and the energy level mismatch at the buried interface constrain the open circuit voltage and cause instability. Herein, a sputter-deposited TiOx thin film is used as a buried interface modification layer to address the aforementioned issues. Utilizing in situ grazing-incidence small-angle X-ray scattering (GISAXS) during the sputter deposition, we monitor and unveil the growth process of the TiOx thin film, identifying a 10 nm thickness optimum. The defects at the buried interface are passivated through tuning the growth, leading to a suppressed non-radiative recombination and improved PCE (from 22.19 % to 23.93 %). The evolution of the device performance and the degradation process of PSCs using operando grazing-incidence wide-angle X-ray scattering (GIWAXS) under the protocol ISOS-L-1I explains the enhanced stability introduced by the buried interface modification via a sputter-deposited TiOx thin layer. The perovskite decomposition process and the detrimental formation of PbI2 are both slowed down by the TiOx thin layer.

Influence of zwitterionic amphiphilic copolymers on heterogeneous gypsum formation: A promising approach for scaling resistance

This study aims to investigate the influence of zwitterionic amphiphilic copolymers (ZACs) in the nucleation and growth of heterogeneous CaSO4 at the zwitterion-water interface, which is crucial for the prevention of mineral scaling and consequent downtime or suboptimal performance in industries like membrane desalination, heat exchangers, and pipeline transportation. In situ grazing incidence small angle X-ray Scattering (GISAXS), and quartz crystal microbalance with dissipation (QCM-D) techniques were used to analyze the evolution of CaSO4 particles on two new ZAC coatings: poly-(trifluoroethyl methacrylate-random-sulfobetaine methacrylate) (PTFEMA-r-SBMA, or PT:SBMA) and poly(trifluoroethyl methacrylate-random-2-methacryloyloxyethyl phosphorylcholine) (PTFEMA-r-MPC, or PT:MPC). The results showed that PT:MPC coatings promoted nucleation but inhibited crystal growth, resulting in slower overall reaction kinetics on PT:MPC coatings compared to PT:SBMA coatings. Interfacial interactions involving the substrates, sulfate minerals, and ions were examined, revealing that calcium ion adsorption, primarily governed by electrostatic attraction, played a crucial role in the nucleation and growth processes on both ZAC coatings. The crystal characterization revealed a phase transition from bassanite to gypsum on both ZAC coatings, suggesting that these zwitterionic materials can influence the mineral phase of heterogeneously formed CaSO4 crystals. These findings enhance our understanding of the fundamental mechanisms underlying heterogeneous CaSO4 scaling in the presence of zwitterionic materials.

(Invited) In Situ and Operando Scattering Studies on Quantum Dot-Based Devices

Colloidal quantum dots (QDs) made e.g. of PbS are attractive for various optoelectronic applications due to their tunable band gap with a large absorption wavelength range from the visible to the near-infrared region. Moreover, due to the high intrinsic permittivity, the exciton binding energy of PbS is smaller than in cadmium chalcogenide QDs and polymer materials, which is beneficial for devices driven by charge carrier generation and transport, e.g. photovoltaics and photodetectors.In this work, we introduce wet chemical deposition methods beyond spin coating such as printing and spray deposition of QDs as a facile and potentially large-scale deposition method for high-performance photodetectors. The inner structures including the inter-dot distance of neighboring QDs and the structure, in the deposited QD solids, are studied by grazing-incidence small-angle X-ray scattering (GISAXS). In addition, the facet orientation of the QDs in the QD solids is characterized by grazing-incidence wide-angle X-ray scattering (GIWAXS). In particular, in situ GISAXS/GIWAXS studies during film formation are able to provide detailed information about the complex kinetic processes [1,2]. Operando GISAXS/GIWAXS studies on QD-based devices such as solar cells bring an in-depth understanding of the degradation mechanisms, which is key for improving the device stability and thereby bringing these novel materials into real-world applications [3]. Superlattice deformation in QD films on flexible substrates via uniaxial strain is followed in situ with GISAXS, providing a fundamental understanding of the impact of strain on the performance of flexible devices based on QD films, such as wearable electronics and next-generation solar cells on flexible substrates [4]. Nanoscale Horiz. 5, 880-885 (2020)Nano Energy 78, 105254 (2020)Energy Environ. Sci. 14, 3420-3429 (2021)Mater. Horizon 8, 383-395 (2023)

Langmuir-Blodgett Transfer of Nanocrystal Monolayers: Layer Compaction, Layer Compression, and Lattice Stretching of the Transferred Layer.

Grazing incidence small angle X-ray scattering (GISAXS) was used to study the structure and interparticle spacing of monolayers of organic ligand-stabilized iron oxide nanocrystals floating at the air-water interface on a Langmuir trough, and after transfer to a solid support via the Langmuir-Blodgett technique. GISAXS measurements of the nanocrystal arrangement at the air-water interface showed that lateral compression decreased the interparticle spacing of continuous films. GISAXS also revealed that Langmuir-Blodgett transfer of the nanocrystal layers to a silicon substrate led to a stretching of the film, with a significant increase in interparticle spacing.

Light-Induced Transformation of Virus-Like Particles on TiO2.

Titanium dioxide (TiO2) shows significant potential as a self-cleaning material to inactivate severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and prevent virus transmission. This study provides insights into the impact of UV-A light on the photocatalytic inactivation of adsorbed SARS-CoV-2 virus-like particles (VLPs) on a TiO2 surface at the molecular and atomic levels. X-ray photoelectron spectroscopy, combined with density functional theory calculations, reveals that spike proteins can adsorb on TiO2 predominantly via their amine and amide functional groups in their amino acids blocks. We employ atomic force microscopy and grazing-incidence small-angle X-ray scattering (GISAXS) to investigate the molecular-scale morphological changes during the inactivation of VLPs on TiO2 under light irradiation. Notably, in situ measurements reveal photoinduced morphological changes of VLPs, resulting in increased particle diameters. These results suggest that the denaturation of structural proteins induced by UV irradiation and oxidation of the virus structure through photocatalytic reactions can take place on the TiO2 surface. The in situ GISAXS measurements under an N2 atmosphere reveal that the virus morphology remains intact under UV light. This provides evidence that the presence of both oxygen and UV light is necessary to initiate photocatalytic reactions on the surface and subsequently inactivate the adsorbed viruses. The chemical insights into the virus inactivation process obtained in this study contribute significantly to the development of solid materials for the inactivation of enveloped viruses.

(Sub-)Picosecond Surface Correlations of Femtosecond Laser Excited Al-Coated Multilayers Observed by Grazing-Incidence X-ray Scattering.

Femtosecond high-intensity laser pulses at intensities surpassing 1014 W/cm2 can generate a diverse range of functional surface nanostructures. Achieving precise control over the production of these functional structures necessitates a thorough understanding of the surface morphology dynamics with nanometer-scale spatial resolution and picosecond-scale temporal resolution. In this study, we show that single XFEL pulses can elucidate structural changes on surfaces induced by laser-generated plasmas using grazing-incidence small-angle X-ray scattering (GISAXS). Using aluminium-coated multilayer samples we distinguish between sub-picosecond (ps) surface morphology dynamics and subsequent multi-ps subsurface density dynamics with nanometer-depth sensitivity. The observed subsurface density dynamics serve to validate advanced simulation models representing matter under extreme conditions. Our findings promise to open new avenues for laser material-nanoprocessing and high-energy-density science.

Early-stage silver growth during sputter deposition on SiO2 and polystyrene – Comparison of biased DC magnetron sputtering, high-power impulse magnetron sputtering (HiPIMS) and bipolar HiPIMS

The integration of silver thin films into optoelectronic devices has gained much interest due to their exceptional properties in terms of conductivity and compatibility with flexible substrates. For this type of application, ultra-thin layers are desirable, because of their optical transparency. Standard direct current magnetron sputtering (DCMS) is known to lead to undesirable formation of islands at low effective film thicknesses on typical substrates like SiO2 or polystyrene (PS). Therefore, in this study, we explore high-power impulse magnetron sputtering (HiPIMS) with optional further acceleration of metal ions by biasing the substrate or an additional positive pulse (bipolar HiPIMS) for the fabrication of ultra-thin silver layers. The morphology and electrical properties of ultra-thin silver layers with selected effective thicknesses are characterized on SiO2 and PS substrates. The growth evolution of characteristic parameters is further investigated by in-situ grazing-incidence small-angle X-ray scattering (GISAXS). The results show that HiPIMS deposition yields films with a higher density of clusters than DCMS leading to a percolation threshold at lower effective film thicknesses. This effect is amplified by further ion acceleration. Thus, we suggest HiPIMS as a promising technique for fabricating ultra-thin, conductive layers on organic and oxide substrates.

Microfabrication through Self‐Ordering of Cracks: Mechanism, Upscaling and Application for Transparent Electrodes

AbstractWhen drying a colloidal solution, cracks appear in the resulting colloidal film. In certain cases, spontaneous order is observed, and cracks form arrays of periodic patterns. Although this phenomenon might be envisioned as a patterning method, overcoming practical challenges is necessary to transform it into a technological tool for microfabrication. This study explores various technological aspects aimed at leveraging the self‐assembly of cracks as a scalable microfabrication tool for large‐scale device production. Through a series of analyses, including time‐resolved Grazing‐Incidence Small‐Angle X‐Ray Scattering (GISAXS), it is offered novel insights into controlling the crack self‐ordering mechanism, minimizing defects, and implementing strategies for large‐scale patterning and pattern transfer. The process proves to be surprisingly robust, maintaining its efficacy with the same colloidal solution even after two years. By introducing biphasic dip‐coating, large‐scale crack patterns up to 100 cm2, while preserving their periodicity and ordering is achieved. As a proof of concept, the use of crack‐patterned colloidal films as masks for fabricating metallic sub‐micrometer objects, that serve as transparent electrodes with adjustable transparency and conductivity is showcased. Overall, this method presents significant advantages over conventional lithography, being cost‐effective, versatile, environmentally friendly, and scalable, thereby offering new perspectives for diverse applications requiring cost‐effective and large‐scale patterning.

Enhanced magnetic anisotropy and its thermal stability in obliquely deposited Co-Film on the nanopatterned substrate

The deliberate manipulation of magnetic anisotropy through controlled adjustments to surface and interface morphology has become important due to its potential applications in spintronics and magnetic memory devices. In the present work, oblique angle deposition (OAD) at 65° to the surface normal on a rippled substrate, keeping nanopatterns on the SiO2 substrate perpendicular to the OAD projection, has been used to induce in-plane uniaxial magnetic anisotropy (UMA) and its thermal stability in cobalt (Co) thin film. Prior to film preparation, the patterned substrate of wavelength 68 ± 4 nm and amplitude 3.4 ± 0.2 nm was prepared separately using a low-energy ion beam erosion (IBE) process. Grazing incidence small-angle X-ray scattering (GISAXS) and magneto-optical Kerr effect (MOKE) techniques have been used for film characterization. While GISAXS provided information about film structure and morphology, MOKE provided information about magnetic properties, thus making it possible to correlate the temperature-dependent evolution of morphology with that of UMA in the film. A clear anisotropy in the growth of Co film is found to result in strong UMA. Unlike previous studies, which typically observe a reduction in UMA strength with thermal annealing, the present work demonstrates a 31 % increase in UMA strength after annealing up to 200 °C, underscoring the importance of oblique angle deposition on nano-rippled substrates for achieving high UMA and ensuring its thermal stability up to moderate temperatures. The appearance of large UMA and its unusual temperature dependence is understood in terms of the shadowing effects and column coalescence, resulting in more robust shape anisotropy. This work provides insights into morphological anisotropy, elucidating the interplay of shadowing effects, shape anisotropy, and dipolar interactions within interacting column and ripple structures. This method gives rise to morphology-induced anisotropy, which can also be applied to other ferromagnetic films to enhance the magnetic anisotropy and ensure thermal stability.

Morphology of Buried Interfaces in Ion-Assisted Magnetron Sputter-Deposited 11B4C-Containing Ni/Ti Multilayer Neutron Optics Investigated by Grazing-Incidence Small-Angle Scattering.

Multilayer neutron optics require precise control of interface morphology for optimal performance. In this work, we investigate the effects of different growth conditions on the interface morphology of Ni/Ti-based multilayers, with a focus on incorporating low-neutron-absorbing 11B4C and using different ion assistance schemes. Grazing-incidence small-angle X-ray scattering was used to probe the structural and morphological details of buried interfaces, revealing that the layers become more strongly correlated and the interfaces form mounds with increasing amounts of 11B4C. Applying high flux ion assistance during growth can reduce mound formation but lead to interface mixing, while a high flux modulated ion assistance scheme with an initial buffer layer grown at low ion energy and the top layer at higher ion energy prevents intermixing. The optimal condition was found to be adding 26.0 atom % 11B4C combined with high flux modulated ion assistance. A multilayer with a period of 48.2 Å and 100 periods was grown under these conditions, and coupled fitting to neutron and X-ray reflectivity data revealed an average interface width of only 2.7 Å, a significant improvement over the current state-of-the-art commercial Ni/Ti multilayers. Overall, our study demonstrates that the addition of 11B4C and the use of high flux modulated ion assistance during growth can significantly improve the interface morphology of Ni/Ti multilayers, leading to improved neutron optics performance.