Grazing-incidence small-angle X-ray scattering (GISAXS) is a technique of choice for providing information about the morphology of nano- and micro-structures at surfaces and interfaces, also in real time. The geometry of the sample, in particular its curvature, has an impact on the observed X-ray scattering signal. There are a multitude of systems with sophisticated geometries (including curvature), ranging from electronic devices on flexible substrates to biological membranes, for which GISAXS could provide valuable information. Therefore, in this work the effect of the sample geometry on the GISAXS signal is addressed. More specifically the influence of the substrate curvature and extent along the X-ray beam is considered. The analytical expressions accounting for the effects of those two geometrical parameters are provided, and the way to include them in the analysis of GISAXS patterns is described. The calculations reveal that no corrections are needed for small samples (length over distance to the detector ratio smaller than 1%) and radius of curvature |R| > 50 m. These results allow for a combination of GISAXS with substrate curvature measurements. The latter technique is a non-destructive in situ and real-time method providing information about the intrinsic stress in a thin film during its growth. Morphological information from GISAXS is supposed to complement this stress information. Herein this methodology is applied to the growth of Ag thin films deposited by magnetron sputtering with N2 plasma additive. The analysis of the GISAXS pattern obtained from the sample, which bends during the deposition, provided morphological parameters of the growing film. This methodology can be useful for understanding of the mechanisms at the nanoscale leading to the observed stress state. The ability to perform GISAXS on curved substrates enables its application to more complex systems.

Nickel-titanium (NiTi) alloys are widely used in orthopedics because of their excellent mechanical properties; however, hypersensitivity remains a concern because of Ni ion release during long-term implantation. To address this issue, we manufactured Ti-Zr-xNb-Sn thin films (x = 10, 15, 17, 20 at.%) using magnetron-sputtering, intended as coatings for NiTi devices. Given the superelasticity of Ti-Zr-Nb-Sn alloys, these coatings are expected to not only suppress the Ni ion release from the NiTi substrate but also reduce the formation of cracks in the coating by accommodating the substrate's deformation. The biocompatibility of the coatings was evaluated both in vitro and in vivo, as well as the potential risk of forming bacterial biofilms. Ti-Zr-xNb-Sn coatings (x = 15, 17 at.%) promoted pre-osteoblast differentiation compared to uncoated NiTi, without increasing the risk of biofilm formation by Staphylococcus epidermidis. The coated NiTi wires were implanted subcutaneously in mice for 28 days, and no strong rejection reaction was observed compared to uncoated NiTi. Additionally, the coatings showed superior corrosion resistance, indicating improved long-term stability. The deposition angle during sputtering influenced cell differentiation, suggesting that both chemical composition and surface morphology contribute to osteogenic responses. Overall, Ti-Zr-Nb-Sn coatings are a promising surface modification strategy for NiTi orthopedic implants.

A quantitative understanding of kinetic effects in metal homoepitaxy is essential for controlling thin-film morphology. Here, we investigate the influence of substrate temperature T and deposition rate F on the morphological evolution of homoepitaxial Cu/Cu(001) layers using an atomistic kinetic Monte Carlo (kMC) model that uniquely resolves diffusion events according to the local atomic environment. This is achieved by introducing the concept of diffusion local surface. The model explicitly incorporates crystallographic facet-dependent diffusion barriers, step-edge barrier for downward diffusion and restricted funneling within a unified framework. It reproduces a rich variety of morphologies depending on deposited thickness and kinetic limitations, including growth instabilities characterized by square-based mound formation aligned along < 110 > directions, mound steepening, and facet development. The early stages of growth are analyzed in the submonolayer regime up to the onset of film continuity, defined by the effective thickness theta cont. This latter exhibits a nonmonotonic temperature dependence, reflecting the competition between random adsorption, anisotropic surface diffusion, upward and downhill mass transport. At intermediate temperatures (200-250 K), theta cont follows a power-law dependence on deposition rate with negative scaling exponents, characteristic of threedimensional growth, while a deposition-rate-independent regime emerges near 300 K. At higher temperatures (400-450 K), enhanced step-descent diffusion promotes smoother, quasi-layer-by-layer growth. The model reproduces the experimentally observed bell-shaped temperature dependence of surface roughness, with a maximum at a characteristic temperature Tw = 300 K for F = 0.1 ML/s, followed by reentrant smooth growth at lower temperatures. We further show that Tw depends on both deposited thickness and deposition rate. More generally, this local-environment-resolved kMC framework provides a predictive tool for linking microscopic diffusion anisotropy to mesoscale morphology in fcc metal homoepitaxy and related growth systems.

The magnetic behaviour of a material can be altered by stresses and defects. As in polycrystalline thin films stress can be measured in situ during a deformation test using X-ray diffraction, we have developed an experimental setup that combines multiple techniques to measure stresses and analyse both mechanical and magnetic behaviours. The capabilities of our experimental setup are presented via the results obtained on a ferromagnetic Ni60Fe40 thin film (20 nm thick) deposited on a polymeric substrate. In order to cover the elastic and the cracking regimes, the films have been subjected to controlled biaxial tensile tests, i.e. two deformation paths, one to create cracks parallel to the applied magnetic field (H), and a second to create cracks perpendicular to H. The evolutions of the hysteresis loops, the measured stress, the damage and the cracking are discussed as functions of the applied deformation. In particular, there is evidence that the measured stress and magnetisation cycles are related by magneto-elastic effects, while the orientation of the cracks relative to the direction of the applied magnetic field shows a magnetic in-plane anisotropy. The stresses distribution in the ferromagnetic Ni60Fe40 thin film is clearly the main factor affecting magnetic behaviour, while crack creation and propagation have a negligible effect.

We report on the microstructural, mechanical and biological properties of novel quaternary TiZrNbSn (in at.%) coatings obtained by magnetron sputter-deposition on Si substrates and Ti disks. In particular, the influence of Nb content on the phase composition and superelastic response of as-deposited Ti-22Zr-xNb-3Sn films are examined. Three compositions were selected corresponding to Nb content x = 10, 17 and 20 at.%. The structure of the films containing 10 and 17 at.% Nb consists of a mix of alpha '' and (3 phases in different proportions while the film with higher Nb content (20 at.%) possesses a single (3 structure. Their superelasticity was studied using a nanoindenter equipped with a spherical tip of 50 mu m diameter. It revealed that the film containing 17 at.% Nb exhibited the highest superelastic behavior with the largest indentation depth recovery ratio values all over the broad range of maximum penetration depths investigated as compared to the values measured for the two other films with 10 and 20 at.% Nb. The biocompatibility tests showed that Ti-22Zr-xNb-3Sn coatings involve high cytocompatibility and do not induce haemolysis, similarly to reference materials (Ti and NiTi).

Nanoscale W1-xSix layers with different Si content were deposited by magnetron sputtering on amorphous silicon layers. The structure and stress evolution during deposition were monitored in situ and in real time. Thus, it was possible to disentangle different origins of stress built-up (interface formation, phase formation, grain growth, and texture) on the nanoscale. It was found that the bcc phase with a composition-dependent texture forms at low Si content (less than 10% Si), but only above a critical thickness. At intermediate Si content (13.9% and 16.5% Si), or low Si content and low thicknesses (less than or similar to 4.5 nm), the beta phase with A15 structure and coexisting phases (bcc or amorphous) form, while a single, amorphous phase is observed at high Si content (greater than or similar to 22% Si). An A15 formation driven by impurities (O,C,N) was excluded by combined in situ x-ray photoelectron spectroscopy and ex situ x-ray diffraction measurements on a second sample series. Ab initio calculations of substitutional bcc and A15 W1-xSix alloys support the formation of A15 at higher Si content. The A15-containing interlayer should be taken into account when discussing the superconductivity of W/Si multilayers. The stress evolution during deposition of W1-xSix was correlated with the microstructure evolution, and compared to similar observations for Mo1-xSix. Due to the crystalline phase (bcc/A15) and bcc texture ([111] and [110]) competition, the structure formation of W1-xSix shows a higher complexity. This explains the wide range of stress states (from tensile to compressive) observed after deposition of W1-xSix. Nanoscale W-Si based stress-compensation layers could be employed for tailoring the stress state of nonepitaxial semiconductor devices.

Nanoscale multilayers offer a convenient way to determine interdiffusion coefficients at low temperatures. However, knowledge regarding the impact of the microstructure on measurements is limited. In the present study, we measure the interdiffusion coefficient in the face-centered cubic (fcc) solid solution of the Ni–Cr system at 440 °C using multilayers composed of alternating layers of pure Ni and Ni78Cr22 (at.%), with a nominal wavelength of 4.5 nm. Three techniques were used to characterize the evolution of the multilayers with annealing time: atom probe tomography (APT), energy-dispersive X-ray spectroscopy (STEM-EDX) and X-ray reflectivity (XRR). Each technique allowed to determine an interdiffusion coefficient. The results evidence that the interdiffusion coefficient is dependent from the technique used to measure it. The primary cause is a very complex microstructure resulting from the elaboration method used to obtain the fine concentration modulation. The analysis of atom probe tomography volumes reveals a high density of columnar grain boundaries (GB) with extended chemical widths. The segregation at GB was measured and a model was derived, allowing to dissociate the contribution of lattice interdiffusion between layers from that of diffusion along and perpendicularly to GBs. The present results could serve as guides for future diffusion investigations involving multilayers.

Ohmic or Schottky contacts in micro-and nano electronic devices are formed by metal-semiconductor bilayer systems, based on elemental metals or thermally more stable metallic compounds (germanides, silicides). The control of their electronic properties remains challenging as their structure formation is not yet fully understood. We have studied the phase and microstructure evolution during sputter deposition and postgrowth annealing of Pd/a-Ge bilayer systems with different Pd/Ge ratios (Pd:Ge, 2Pd:Ge, and 4Pd:Ge). The room -temperature deposition of up to 30 nm Pd was monitored by simultaneous, in situ synchrotron X-ray diffraction, X-ray reflectivity, and optical stress measurements. With this portfolio of complementary real-time methods, we could identify the microstructural origins of the resistivity evolution during contact formation: Real-time X-ray diffraction measurements indicate a coherent, epitaxial growth of Pd(111) on the individual crystallites of the initially forming, polycrystalline Pd2Ge[111] layer. The crystallization of the Pd2Ge interfacial layer causes a characteristic change in the real-time wafer curvature (tensile peak), and a significant drop of the resistivity after 1.5 nm Pd deposition. In addition, we could confirm the isostructural interface formation of Pd/a-Ge and Pd/a-Si. Subtle differences between both interfaces originate from the lattice mismatch at the interface between compound and metal. The solid-state reaction during subsequent annealing was studied by real-time X-ray diffraction and complementary UHV surface analysis. We could establish the link between phase and microstructure formation during deposition and annealing-induced solid-state reaction: The thermally induced reaction between Pd and a-Ge proceeds via diffusion-controlled growth of the Pd2Ge seed crystallites. The second-phase (PdGe) formation is nucleation-controlled and takes place only when a sufficient Ge reservoir exists. The real-time access to structure and electronic properties on the nanoscale opens new paths for the knowledge-based formation of ultrathin metal/semiconductor contacts.

This work is an experimental study on electrooptical Kerr effect in hydrofluoroether HFE-7100. It is part of a scientific project aiming to better understand electrohydrodynamic (EHD) behavior and hence optimize EHD systems. The electro-optical Kerr effect is a nonintrusive method that allows to study the development of charged layers at the electrode/liquid interface. In this paper, the authors examine the applicability of the Kerr effect method on HFE-7100, a dielectric liquid that has proven to be very efficient in EHD applications. The system consists of a monochromatic green laser source and a rectilinear polariscope. The Kerr cell has two planar electrodes on which a high sinusoidal voltage is applied. The light intensity of the obtained images is then analyzed. The Kerr coefficient value B of the HFE-7100 is deduced to be $\mathrm{B}= 2.7 \times 10^{-14}\mathrm{V}/ \mathrm{m}^{2}$, a value that is comparable to that of purified water. Kerr images are presented, and their qualitative analysis demonstrates the presence of space charge. This work proves that HFE has a good sensitivity to the Kerr effect.

The interdiffusion coefficient in the Ni/Cr system was determined at low temperature using Ni/Ni0.78Cr0.22 nanometer-scale multilayers with periods of 3.65 and 4.50 nm. X-ray reflectivity measurements were carried out to monitor the 1st Bragg peak intensity with annealing time, at both 400 and 450 ? temperatures. The obtained kinetics of the composition modulation decay allowed determining the interdiffusion coefficients of the uniform final solid solution, Ni0.89Cr0.11. Values in the order of 10 - 21 to 10-20 cm(2).s(-1) at 400 ? and 450 ?, respectively, were found, in line with extrapolations from data of Cr diffusion obtained at higher temperature.

The ability to design electrohydrodynamic systems with minimal risk of breakdown is essential for having a higher security level of performance. In order to achieve this goal, the dielectric strength of the operating liquid must not be reached. In addition to that, it is important to investigate the current-voltage characteristics of the working liquid to have a better understanding of the system's response. Therefore, this work has two main objectives: to investigate the temperature effect on the dielectric strength of Hydrofluoroether 7100, and to study the electric behavior of this same liquid under high electric fields at different temperatures. Results show that the breakdown voltage increases with temperature. The inter-electrode distance seems to have a greater influence on the breakdown voltage at high temperatures than at low temperatures. Temperature also proved to have an important effect on the shape of the current-voltage curves. The injection zone's threshold increases with temperature. This zone is more pronounced for temperatures lower than 25°C.

Abstract A new process for elaborating continuously organic-inorganic hybrid materials by reactive extrusion is presented. This synthesis consists in formulating a copolymer of ethylene and vinyl acetate (EVA)/tetrapropoxysilane (TPOS or Si(OC3H7)4)/catalyst blend by a corotating twin screw extruder followed by two successive reaction steps: on line microwave crosslinking reaction and hydrolysis-condensation reactions leading to a silica network cografted onto the organic matrix. Extrusion feed rate (Q), temperature, microwave oven power (P), and microwave curing time (tmw) were studied. Crosslinking density was evaluated before and after hydrolysis-condensation reactions and compared with the previous results obtained in static conditions. These materials tailored by an on line process present a permanent elasticity at high temperature (up to 200 °C) and a certain optical transparency. This new approach offers the possibility to synthesize massive samples based on organic-inorganic hybrid material.

Kinetic Monte Carlo (kMC) atomistic computations using MODENA code were employed to simulate the growth of columnar TiN thin films under oblique angle deposition geometry. The influence of substrate temperature (300, 400 and 500 K) on the morphology (column tilt angle, average layer density, compactness, surface roughness) of the layers was studied by varying the inclination angle alpha of the substrate from 5 degrees to 85 degrees with respect to the centerline of the source. Two types of simulations were considered in this work: the first one assumes a collimated flux (CF) of incident particles and the second one grasps the angular distribution of sputtered Ti particles to closely mimic the magnetron sputtering (MS) conditions. The formation of separated columns with high aspect ratio, and tilted in the direction of the incident particles flux, is observed for alpha > 35 degrees for the two types of particle flux. The column width and tilt angle, the average layer density and the compactness of the TiN films are found to increase with increasing substrate temperature, due to enhanced surface diffusion. The column tilt angle beta increases from 3 degrees to 60 degrees with increasing alpha for the CF case, while it saturates to approx. 35 degrees when the MS distribution is considered. The relationship between beta and alpha, and their temperature dependence, are discussed and compared to experimental results obtained on sputter-deposited TiN films, as well as with other results and models reported in the literature. The code also reproduces morphological features common to most films produced at glancing angles, such as column broadening with increasing thickness and their anisotropic aggregation (bundling association) in the transverse direction.

HFE-7000 and HFE-7100 have shown a promising importance in the electrohydrodynamic (EHD) domain. Their dielectric properties are investigated in a temperature range between -20 and 60 degrees C for relative permittivity and electric conductivity and between -20 and 80 degrees C for breakdown voltage. The aim is to electrically characterize these liquids and to develop experimental models to be used in numerical simulations. Mathematical models of electric properties are essential for understanding the physical phenomena that can affect the performance of EHD systems. The development of these models can then help design more reliable EHD devices and optimize their performance.

Continued downscaling of functional layers for key enabling devices has prompted the development of characterization tools to probe and dynamically control thin film formation stages and ensure the desired film morphology and functionalities in terms of, e.g., layer surface smoothness or electrical properties. In this work, we review the combined use of in situ and real-time optical (wafer curvature, spectroscopic ellipsometry) and electrical probes for gaining insights into the early growth stages of magnetron-sputter-deposited films. Data are reported for a large variety of metals characterized by different atomic mobilities and interface reactivities. For fcc noble-metal films (Ag, Cu, Pd) exhibiting a pronounced three-dimensional growth on weakly-interacting substrates (SiO2, amorphous carbon (a-C)), wafer curvature, spectroscopic ellipsometry, and resistivity techniques are shown to be complementary in studying the morphological evolution of discontinuous layers, and determining the percolation threshold and the onset of continuous film formation. The influence of growth kinetics (in terms of intrinsic atomic mobility, substrate temperature, deposition rate, deposition flux temporal profile) and the effect of deposited energy (through changes in working pressure or bias voltage) on the various morphological transition thicknesses is critically examined. For bcc transition metals, like Fe and Mo deposited on a-Si, in situ and real-time growth monitoring data exhibit transient features at a critical layer thickness of ~2 nm, which is a fingerprint of an interface-mediated crystalline-to-amorphous phase transition, while such behavior is not observed for Ta films that crystallize into their metastable tetragonal β-Ta allotropic phase. The potential of optical and electrical diagnostic tools is also explored to reveal complex interfacial reactions and their effect on growth of Pd films on a-Si or a-Ge interlayers. For all case studies presented in the article, in situ data are complemented with and benchmarked against ex situ structural and morphological analyses.

Nowadays, heat transfer enhancement devices are becoming very essential in many applications. Most of electronic devices, from the simplest to the most sophisticated, contain processors. Advanced processors require efficient cooling for an optimal performance. Due to the growing interest in faster and lighter devices, researchers always seek to innovate and optimize cooling strategies. In spatial applications, the use of typical cooling systems can cause complications due to the vibrations during takeoff and due to zero gravity effects. Electrohydrodynamic (EHD) pumping, which is based on the interaction of a dielectric liquid with an electric field, could present a solution to all these challenges. EHD pumps were considered a breakthrough in the field of cooling since they demonstrate many advantages over other types of pumps. EHD devices are less power consuming, lighter and cheaper. They don't have moving parts and they are suitable for microgravity applications. The hydrofluoroethers (HFE) are dielectric liquids that could be ideally utilized in these pumps for many applications. Being dielectric fluids with eco-friendly properties, HFEs could replace CFCs, HFCs, HCFCs, and PFCs. Due to their promising EHD applications, studies must be done to investigate the variation of their dielectric behavior with electric field and with temperature. This work presents an experimental investigation of the dielectric characteristics of HFE-7000 with temperature variations. Understanding this aspect can help enhance and optimize the performance of EHD systems.

Synchrotron experiments combining real-time stress, X-ray diffraction, and X-ray reflectivity measurements, complemented by in situ electron diffraction and photon electron spectroscopy measurements, revealed a detailed picture of the interfacial silicide formation during deposition of ultrathin Pd layers on amorphous silicon. Initially, an amorphous Pd2Si interlayer is formed. At a critical thickness of 2.3 nm, this layer crystallizes and the resulting volume reduction leads to a tensile stress buildup. The [111] textured Pd2Si layer continues to grow up to a thickness of ≈3.7 nm and is subsequently covered by a Pd layer with [111] texture. The tensile stress relaxes already during Pd2Si growth. A comparison between the texture formation on SiOx and a-Si shows that the silicide layer serves as a template for the Pd layer, resulting in a surprisingly narrow texture of only 3° after 800 s Pd deposition. The texture formation of Pd and Pd2Si can be explained by the low lattice mismatch between Pd(111) and Pd2Si(111). The combined experimental results indicate a similar interface formation mechanism for Pd on a-Si and c-Si, whereas the resulting silicide texture depends on the Si surface. A new strain relaxation mechanism via grain boundary diffusion is proposed, taking into account the influence of the thickness-dependent crystallization on the material transport through the silicide layer. In combination with the small lattice mismatch, the grain boundary diffusion facilitates the growth of Pd clusters, explaining thus the well-defined thickness of the interfacial silicide layer, which limits the miniaturization of self-organized silicide layers for microelectronic devices.

Non-magnetic (NM) metals with strong spin-orbit coupling have been recently explored as a probe of interface magnetism on ferromagnetic insulators (FMI) by means of the spin Hall magnetoresistance (SMR) effect. In NM/FMI heterostructures, increasing the spin mixing conductance (SMC) at the interface comes as an important step towards devices with maximized SMR. Here we report on the study of SMR in Pt/Fe3O4 bilayers at cryogenic temperature, and identify a strong dependence of the determined real part of the complex SMC on the interface roughness. We tune the roughness of the Pt/Fe3O4 interface by controlling the growth conditions of the Fe3O4 films, namely by varying the thickness, growth technique, and post-annealing processes. Field-dependent and angular-dependent magnetoresistance measurements sustain the clear observation of SMR. The determined real part of the complex SMC of the Pt/Fe3O4 bilayers ranges from 4.96 × 1014 Ω−1 m−2 to 7.16 × 1014 Ω−1 m−2 and increases with the roughness of the Fe3O4 underlayer. We demonstrate experimentally that the interface morphology, acting as an effective interlayer potential, leads to an enhancement of the spin mixing conductance.

Nanostructured columnar titanium nitride (TiN) thin films were produced by oblique angle deposition using reactive magnetron sputtering. The influence of the angular distribution of the incoming particle flux on the resulting film morphology (column tilt angle, porosity, surface roughness) was studied by varying the inclination angle alpha of the substrate at two different working pressures, 0.3 and 0.5 Pa. The microstructural features and columns tilt angles beta(exp) determined experimentally were compared to those simulated from two kinetic Monte Carlo (KMC) models. With increasing pressure, the TiN columns were found to be less defined but no significant changes in beta(exp) were revealed. Both KMC models satisfactorily reproduced the experimental findings, the agreement being closer at 0.5 Pa. The evolution of beta angle is also discussed with respect to the resulting incidence angle theta(res) of the incoming flux, this latter quantity accounting for the local incidence angle of individual particles, which may greatly differ from the geometrical angle alpha, especially at high working pressure due to the incoming particle-gas collisions. Crossover phenomena between the 0.3 and 0.5 Pa series were revealed from the evolution of the film resistivity, as well as simulated layer density and surface roughness versus alpha angle. (C) 2018 Elsevier Ltd.