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The self-diffusion of lithium in congruent LiNbO3 single crystals was investigated at low temperatures between 379 and 523 K by neutron reflectometry. From measurements on 6LiNbO3 (amorphous film)/natLiNbO3 (single crystal) samples, Li self-diffusivities were determined in single crystals down to extremely low values of 1 × 10−25 m2 s−1 on small length scales of 1–10 nm. The measured diffusivities are in excellent agreement with (extrapolated) literature data obtained by experiments based on Secondary Ion Mass Spectrometry and Impedance Spectroscopy. The tracer diffusivities can be described by a single Arrhenius line over ten orders of magnitude with an activation enthalpy of 1.33 eV, which corresponds to the migration energy of a single Li vacancy. A deviation from the Arrhenius behaviour at low temperatures, e.g., due to defect cluster formation is not observed. [ABSTRACT FROM AUTHOR]

The high brilliance at the European Spallation Source (ESS) will allow for performing experiments with much smaller samples than at present neutron facilities and in much more complex sample environments. However the higher flux also results in higher background from unwanted neutrons not originating from scattering of the sample. We here present a new design idea for beam delivery, where a 165 m ballistic guide system with good transport properties is followed by a 4–8 m SELENE guide system similar to Montel optics used for X-ray optics. We have investigated the system by detailed Monte-Carlo simulations using McStas. We show that under certain conditions, this set-up works surprisingly well, with a brilliance transfer of 20–60% for neutrons of wavelength 4 Å and above. We demonstrate that the guide system is able to focus the beam almost perfectly onto samples sizes in the range of 0.1–2 mm. We furthermore show that our SELENE system is insensitive to gravity and to realistic values of guide waviness. We argue that this guide system can be useful as an optional guide insert when small samples are used in the vicinity of bulky sample environment, e.g. for high-field or high-pressure experiments. [ABSTRACT FROM AUTHOR]

Abstract: In various fields of neutron scattering there is a tendency to use smaller and smaller samples. There are various reasons for this, e.g. the limited size in high pressure cells, the restrictions given by growth methods of thin films, or the impossibility to grow larger single crystals. With conventional guides this leads to the situation that a white beam with some 50cm2 cross-section and a broad divergence is to illuminate a sample of some mm2 area. Thus more than 99% of the neutrons leaving the guide are not needed and cause background and radiation problems. It is suggested to change the order of the optical elements and the design of the guide section to filter neutrons not intended to hit the sample as early as possible. As an example a set-up for specular reflectivity on small samples is presented. A double monochromator some meters behind the source cuts away all neutrons of the wrong wavelength even before they enter the guide. The guide itself is one branch of an ellipse. It maps the divergent beam from the monochromator to a convergent beam at the sample position. An entry aperture at the first focal point, a bit larger than the sample, guarantees that just enough neutrons enter the guide to bath the sample. There is no direct line of sight to the source and the guide ends far away from the sample position, so that there are only few spacial restrictions. Detailed McStas calculations and a design study for a down-scaled test device, both for reflectometry and diffraction, are presented. [Copyright &y& Elsevier]

LixLaySrzMnO3 thin films of various compositions (x,y,z) have been grown using pulsed laser deposition. The compositions of the films have been studied as a function of deposition temperature, target-to-substrate distance and deposition pressure with respect to different cation ratios of the targets by inductively coupled plasma mass spectrometry. When growing multi-elemental oxide thin films containing lithium (with its large mass difference to other elements), lithium loss is most probably inevitable. But the desired thin film composition can be achieved by selecting specific growth conditions and different target compositions. The experiments also elucidate some of the mechanisms behind the incongruent lithium transfer from the targets to thin films. [ABSTRACT FROM AUTHOR]

We demonstrate a stationary helium gas density gradient which is needed for a proposed novel low-energy μ + beam line. In a closed system with constant pressure the corresponding density gradient is only a function of the temperature. In a neutron radiography experiment two gas cells with different geometries were filled with 3 He gas at constant pressures of about 10 mbar. Temperatures in the range from 6 K to 40 K were applied and density distributions with a maximum to minimum density ratio of larger than 3 were realized. The distribution was investigated employing the strongly neutron absorbing isotope 3 He. A simple one-dimensional approach derived from Fourier׳s law describes the obtained gas density with a deviation < 2 % . [ABSTRACT FROM AUTHOR]

We study the element-specific magnetic depth profiles of a YBa2Cu3O7/La2/3Ca1/3MnO3 (YBCO/LCMO) superlattice using soft x-ray resonant magnetic reflectometry (XRMR). This allows us to study the magnetic proximity effect (MPE) that is observed at the YBCO/LCMO interface, characterized by the occurrence of a depleted layer on the manganite side and an induced magnetization in the YBCO. Using the element-specific depth profiling capability of XRMR, we show that the Cu moments (0.28µB is per interfacial Cu ion) reside on the YBCO side of the interface and originate from the CuO2 plane that is located at the interface. We also rule out the possibility that the Cu moments originate from the migration of Cu atoms into the LCMO layer (interdiffusion). Finally, we show that the suppression of the Mn moment on the LCMO side is only partial for the interface of LCMO deposited on YBCO (0.628µB per Mn ion), compared to the complete suppression for the interface of YBCO deposited on LCMO. These differences in the LCMO depleted layers indicate the strong variations in the MPE between the case of YBCO on LCMO and the case of LCMO on YBCO. [ABSTRACT FROM AUTHOR]

In view of the trend towards smaller samples and experiments under extreme conditions it is important to deliver small and homogeneous neutron beams to the sample area. For this purpose, elliptic and/or Montel mirrors are ideally suited as the phase space of the neutrons can be defined far away from the sample. Therefore, only the useful neutrons will arrive at the sample position leading to a very low background. We demonstrate the ease of designing neutron transport systems using simple numeric tools, which are verified using Monte-Carlo simulations that allow taking into account effects of gravity and finite beam size. It is shown that a significant part of the brilliance can be transferred from the moderator to the sample. Our results may have a serious impact on the design of instruments at spallation sources such as the European Spallation Source (ESS) in Lund, Sweden. [ABSTRACT FROM AUTHOR]

Single phase and strained LuMnO3 thin films are discovered to display coexisting ferromagnetic and antiferromagnetic orders. A large moment ferromagnetism (≈ 1μB) which is absent in bulk samples, is shown to display a magnetic moment distribution that is peaked at the highly strained substrate-film interface. We further show that the strain-induced ferromagnetism and the antiferromagnetic order are coupled via an exchange field, therefore demonstrating strained rare-earth manganite thin films as promising candidate systems for new multifunctional devices. [ABSTRACT FROM AUTHOR]

Highlights: [•] Fe/Si multilayers were deposited using evaporation sputtering techniques. [•] Difference in surface free energy of Fe and Si leads to asymmetric interfaces. [•] A silicide layer is formed due to spontaneous interdiffusion. [•] Thickness of silicide layer is more in evaporated samples. [•] Silicide layer formed is non-magnetic. [Copyright &y& Elsevier]

In this work, we studied a correlation between spin-dependent scattering and interface roughness in Cu/Co multilayers. In Cu/Co multilayers, Cu-on-Co and Co-on-Cu interfaces are not identical because of significant difference in the surface free energy of Cu and Co. By adding Ag surfactant during the growth of multilayer structure, we found that the difference between the interface roughness of two interfaces can be minimized. By doing this we found that the strength of anti-ferromagnetic coupling increases significantly. A comparison between normalized magnetoresistance to antiferromagnetic fraction with interface roughness shows the variation of spin-dependent scattering at the interface in Cu/Co multilayers. [ABSTRACT FROM AUTHOR]

Abstract: The unusual magnetic behaviour of a Pd/Nb67Ti33/Pd heterostructure was investigated using polarised neutron reflectivity technique. On application of a large in-plane magnetic field, Stoner enhanced paramagnet Pd was found to influence the magnetic state of the Nb67Ti33 layer both above and below the superconducting transition temperature T c significantly. Unlike the case of a conventional proximity effect for a superconductor/metallic heterostructure, the pair correlation in the superconducting state has been found to be more stable in the higher field limit compared to its low field counterpart, possibly signaturing a ‘novel’ coupled state in the system. The superconducting state in Nb67Ti33 has been found to be diamagnetic in nature at all the fields that can be fitted using a Meissner kind of behaviour in the high field limit. The magnetic properties of Pd and Nb67Ti33 are in excellent agreement with those measured using bulk magnetisation measurements. [Copyright &y& Elsevier]

Using polarized neutron reflectometry (PNR) we have investigated a [YBa2Cu3O7(10nm)/La2/3Ca1/3MnO3(9nm)]10(YBCO/LCMO) superlattice grown by pulsed laser deposition on a La0.3Sr0.7Al0.65Ta0.35O3 (LSAT) substrate. Due to the high structural quality of the superlattice and the substrate, the specular reflectivity signal extends with a high signal-to-background ratio beyond the fourth-order superlattice Bragg peak. This allows us to obtain more detailed and reliable information about the magnetic depth profile than in previous PNR studies on similar superlattices that were partially impeded by problems related to the low-temperature structural transitions of the SrTiO3 substrates. In agreement with the previous reports, our PNR data reveal a strong magnetic proximity effect showing that the depth profile of the magnetic potential differs significantly from the one of the nuclear potential that is given by the YBCO and LCMO layer thickness. We present fits of the PNR data using different simple blocklike models for which either a large ferromagnetic moment is induced on the YBCO side of the interfaces or the ferromagnetic order is suppressed on the LCMO side. We show that a good agreement with the PNR data and with the average magnetization as obtained from dc magnetization data can only be obtained with the latter model where a so-called depleted layer with a strongly suppressed ferromagnetic moment develops on the LCMO side of the interfaces. We also show that the PNR data are still compatible with the presence of a small, ferromagnetic Cu moment of 0.25 μB on the YBCO side that was previously identified with x-ray magnetic circular dichroism and x-ray resonant magnetic reflectometry measurements on the same superlattice [D. K. Satapathy et al. Phys. Rev. Lett. 108 197201 (2012)]. We discuss that the depleted layer thus should not be mistaken with a "dead" layer that is entirely nonmagnetic but rather may contain a canted antiferromagnetic or an oscillatory type of ordering of the Mn moments that is not detected with the PNR technique. [ABSTRACT FROM AUTHOR]

Using neutron reflectometry and resonant x-ray techniques we studied the magnetic proximity effect (MPE) in superlattices composed of superconducting YBa2Cu307 and ferromagnetic-metallic Lao.67Cao.33Mn03 or ferromagnetic-insulating LaMn03+&b.delta;. We find that the MPE strongly depends on the electronic state of the manganite layers, being pronounced for the ferromagnetic-metallic Lao.67Cao.33Mn03 and almost absent for ferromagnetic-insulating LaMn03+&b.delta;. We also detail the change of the magnetic depth profile due to the MPE and provide evidence for its intrinsic nature. [ABSTRACT FROM AUTHOR]

Grain boundary self-diffusion in Type-C regime was investigated in nano-crystalline bcc iron at low temperatures between 100 and 250 °C using neutron reflectometry in combination with [natFe(7 nm)/57Fe(3 nm)]10 isotope multilayers. The method allows to determine diffusivities in a stable nanostructure without concurrent grain growth. An activation enthalpy of diffusion of (0.9 ± 0.3) eV is found, comparable to the value of coarse-grained Fe. [ABSTRACT FROM AUTHOR]

Heteroepitaxial superlattices of [YBa2Cu3O7(n)/La0.67Ca0.33Mn03(m)]x (YBCO/LCMO), where n and m are the number of YBCO and LCMO monolayers and x the number of bilayer repetitions, have been grown with pulsed laser deposition on NdGaO3 (110) and Sr0.7La0.3Al0.65Ta0.35O3 (001). These substrates are well lattice matched with YBCO and LCMO and. unlike the commonly used SrTiO3, they do not give rise to complex and uncontrolled strain effects at low temperature. The growth dynamics and the structure have been studied in situ with reflection high-energy electron diffraction and ex situ with scanning transmission electron microscopy, x-ray diffraction, and neutron reflectometry. The individual layers are found to be flat and continuous over long lateral distances with sharp and coherent interfaces and with a well-defined diickness of the individual layer. The only visible defects are antiphase boundaries in the YBCO layers that originate from perovskite unit-cell height steps at the interfaces with the LCMO layers. We also find that the first YBCO monolayer at the interface with LCMO has an unusual growth dynamics and is lacking the CuO chain layer, while the subsequent YBCO layers have the regular Y-123 structure. Accordingly, the Cu02 bilayers at both the LCMO/YBCO and the YBCO/LCMO interfaces are lacking one of their neighboring CuO chain layers and, thus, half of their hole-doping reservoir. Nevertheless, from electric transport measurements on a superlattice with n = 2 we obtain evidence that the interfacial CuO32 bilayers remain conducting and even exhibit the onset of a superconducting transition at very low temperature. Finally, we show from dc magnetization and neutron reflectometry measurements that the LCMO layers are strongly ferromagnetic [ABSTRACT FROM AUTHOR]

Abstract: Iron mononitride, FeN, is known to exist in different phases and there is a debate on the exact crystal type and the coexistence of these phases. We prepared single phase iron mononitride thin films by magnetron sputtering with various deposition rates (sputtering power) and investigated them with X-ray diffraction, neutron reflectometry and low temperature and high magnetic field Mössbauer spectroscopy. It was observed that with an increase in the sputtering power a more disordered structure is formed while the local chemical environment of iron remains unaffected. The low temperature and high magnetic field Mössbauer spectroscopy measurements confirmed that the FeN phase is paramagnetic at 5K and an applied magnetic field of 5T reflects magnetic splitting caused by the applied field. The obtained results are discussed in this study. [Copyright &y& Elsevier]

Abstract: Thin metallic films produced by sputtering methods show a considerable amount of non-equilibrium point defects, which annihilate during annealing close to room temperature. In order to identify type and migration enthalpy of these defects, volume self-diffusion is studied in ion-beam sputtered nanocrystalline Fe films on short time scales (<20min) and for short diffusion lengths (<2nm) between 250 and 510°C. Neutron reflectometry is applied on [natFe (7nm)/57Fe(3nm)]15 isotope multilayers in order to derive the diffusivities. The diffusivities decrease strongly as a function of annealing time as a result of an annihilation process of non-equilibrium point defects. The initial diffusivities present at the beginning of annealing follow the Arrhenius law with an activation enthalpy of 0.8eV, which is identified as the migration enthalpy of single vacancies by comparison to the literature. The motion of these non-equilibrium vacancies seems to be the dominating mechanism in the annihilation procedure. From the pre-exponential factor an initial vacancy concentration of about 10−12 (mole fraction) can be assessed, which is significantly higher than the corresponding thermal equilibrium value. [Copyright &y& Elsevier]

Self-diffusion experiments based on neutron reflectometry and isotope multilayers in ultrafine-grained copper have been reported. The capability of this method to determine diffusion lengths in the order of 1nm enables the measurement of volume diffusivities in the type B kinetic regime identical to previously published data on single crystals. Such results are difficult to achieve by classical methods of diffusivity determination, such as the radiotracer method, due to limitations of the depth resolution. [Copyright &y& Elsevier]

Abstract: A transmission neutron polariser (Fe/Si supermirror) has been successfully implemented in the small angle neutron scattering instrument SANS-I at the SINQ neutron source. The polariser is needed for investigations of magnetic nanostructures as well as for spin contrast variation techniques relying on the spin-dependent neutron scattering length of polarised nuclei. The V-shaped polariser is installed in the first section of the collimator system of the SANS instrument and its performance is optimised for neutrons with a wavelength between 0.5 and 1.0nm. For a precise polarisation analysis of a beam with selectable incident divergence, such as in SANS experiments, an opaque spin filter is ideal. We used a solid polarised proton target exploiting the strong spin-dependent neutron scattering cross-section of hydrogen and determined the neutron beam polarisation to a precision of for different collimations in a broad wavelength band. [Copyright &y& Elsevier]

Abstract: We have investigated the focusing properties of the prototype of a transportable elliptic neutron guide. We demonstrate that the elliptic guide allows to map a point-like neutron source in one focal point on a tiny spot in the other focal point. We also show that an elliptically tapered neutron guide increases the neutron flux density in the focal point by at least one order of magnitude compared to the flux density of the original neutron beam. This allows to use neutron beams more efficiently in experiments with small samples. We used the elliptic neutron guide to focus a several centimeters wide neutron beam on a tiny sample with the dimensions and easily detected the ordered moment of this antiferromagnetic insulator. This suggests that many more small samples, in particular in high pressure experiments, can be studied with elliptic neutron guides. [Copyright &y& Elsevier]

Abstract: A new high resolution (400nm) Fresnel Zone Plate (ZP) of 1mm diameter has been designed and produced in order to accurately measure its spatial resolution and efficiency. This experiment is an extension of the previous tests performed to measure the efficiency of these devices. The measurements were carried out on the diffractometer Morpheus at PSI using a new ZP designed to obtain a small focal length of 0.833 m at 4.7Å. In this experiment a 0.8mm edge square neutron source at 4.7Åwas demagnified by the ZP by a factor 2 down to about 0.4mm at 1.24m distance from the ZP. With this configuration, using a Gd knife edge, we determined the transverse profile of the image with a spatial accuracy of 0.01mm. In addition an appropriate configuration was used to measure the efficiency of the ZP, which was equal to , to be compared to 0.325, that is the ideal value at 4.7Å. The result for the ZP resolution suggests that the image has a broadening in the range of 0.01mm, corresponding to an effective wave front coherence over a distance greater than , to be compared to some as deduced from the indetermination principle, according to the beam divergence. Numerical simulations of the ZP are performed with a partially coherent wave front to show the effect of the phase variation on the intensity at different positions. [Copyright &y& Elsevier]

Abstract: Self-diffusion of the atomic constituents in the solid state is a fundamental transport process that controls various materials properties. With established methods of diffusivity determination it is only possible to measure diffusion processes on a length scale down to 10nm at corresponding diffusivities of 10−23 m2 s−1. However, for complex materials like amorphous or nano-structured solids the given values are often not sufficient for a proper characterization. Consequently, it is necessary to detect diffusion length well below 1nm. Here, we present the method of neutron reflectometry on isotope multilayers. For two model systems, an amorphous semiconductor and an amorphous metallic alloy, the efficiency of this method is demonstrated to detect minimum diffusion lengths of only 0.6–0.7nm. It is further shown that diffusivities can be derived which are more than two orders of magnitude lower than those obtainable with conventional methods. Prospects of this method in order to solve actual kinetic problems in materials science are given. [Copyright &y& Elsevier]

Abstract: A detailed reflectometry study of Langmuir–Blodgett multilayers composed of a polyelectrolyte-amphiphile complex (PAC) is presented. The PAC is self-assembled from metal ions, ditopic bis-terpyridines and amphiphiles. The structure as well as the vacuum stability of the LB multilayer is investigated by soft x-ray reflectometry. The multilayer has a periodicity of 57 Å, which corresponds to an architecture of flat-lying MEPE rods and upright standing amphiphiles (hexadecyl phosphate, DHP). The films remain stable under high vacuum conditions. X-ray magnetic circular dichroism reveals a magnetic moment of carried by the iron ions within the films. Using spin-resolved neutron reflectometry, Langmuir–Blodgett-films of PAC are identified as magnetic multilayer systems with the same characteristic -spacing as it is found for the structural multilayer periodicity. The separation of the edges of total external reflection for spin up and spin down neutrons in presence of a magnetic moment is studied by time-of-flight neutron reflectometry. [Copyright &y& Elsevier]

Abstract: Nickel/titanium multilayers (ML) and supermirrors (SM) were fabricated by DC magnetron sputtering on glass or Si (100) substrates. It was possible to increase the reflectivity of ML and SM by the deposition of an ultrathin Cr layer at the Ni/Ti interfaces. Interdiffusion decreases when the Ni and Ti are separated by a covering Cr layer (3Å), whereas, in the range where the Cr interlayer thickness is higher than the Ni/Ti interdiffusion depth (approximately 6Å) or the surface roughness, the growth of a closed Cr layer is prohibited reducing the reflectivity. The presence of a 10Å Cr interlayer on some Ti layers also results in enhanced reflectivities due to a smoothing effect of the interface for the following layers. The reflectivities of two monochromators for and a bandwidth (Δλ/λ) of 6% and 12% reach a value of approximately 0.90. [Copyright &y& Elsevier]

Ge x Si 1- x alloys are gaining renewed interest for many applications in electronics and optics, especially for miniaturized devices showing quantum size effects. Point defects and atomic diffusion play a crucial role in miniaturized and metastable systems. In the present work, Ge self-diffusion in sputter deposited amorphous Ge x Si 1- x alloys is studied in situ as a function of Ge content x = 0.13, 0.43, 0.8, and 1.0 by neutron reflectometry. The determined Ge self-diffusivities obey the Arrhenius law in the investigated temperature ranges. The higher the Ge content x , the higher the Ge self-diffusivity at the same temperature. The activation enthalpy decreases with x from 4.4 eV for self-diffusion in pure silicon films to about 2 eV self-diffusion in Ge 0.8 Si 0.2 and Ge. The decrease of the activation enthalpy for amorphous Ge x Si 1- x is similar to the case of crystalline Ge x Si 1- x . Possible explanations are discussed., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

The utilization of polarized neutrons is of great importance in scientific disciplines spanning materials science, physics, biology, and chemistry. However, state-of-the-art multilayer polarizing neutron optics have limitations, particularly low specular reflectivity and polarization at higher scattering vectors/angles, and the requirement of high external magnetic fields to saturate the polarizer magnetization. Here, we show that, by incorporating 11 B 4 C into Fe/Si multilayers, amorphization and smooth interfaces can be achieved, yielding higher neutron reflectivity, less diffuse scattering, and higher polarization. Magnetic coercivity is eliminated, and magnetic saturation can be reached at low external fields (>2 militesla). This approach offers prospects for substantial improvement in polarizing neutron optics with nonintrusive positioning of the polarizer, enhanced flux, increased data accuracy, and further polarizing/analyzing methods at neutron scattering facilities.

In this work, we investigated the effect of Ag doping (2-20 at.%) on the phase formation of iron mononitride (FeN) thin films. Together with deposition of FeN using reactive dc magnetron sputtering, Ag was also co-sputtered at various doping levels between 2-20 at.%. We found that doping of Ag around 5 at.% is optimum to not only improve the thermal stability of FeN but also to reduce intrinsic defects that are invariably present in (even in epitaxial) FeN. Conversion electron Mössbauer spectroscopy and N K-edge x-ray near edge absorption measurements clearly reveal a reduction of defects in Ag doped FeN samples. Moreover, Fe self-diffusion measurements carried out using secondary ion mass spectroscopy depth-profiling and polarized neutron reflectivity in 57 Fe enriched samples exhibit an appreciable reduction in Fe self-diffusion in Ag doped FeN samples. Ag being immiscible with Fe and non-reactive with N, occupies grain-boundary positions as nanoparticles and prohibits the fast Fe self-diffusion in FeN., (© 2021 IOP Publishing Ltd.)

LaTiO x N y oxynitride thin films are employed to study the surface modifications at the solid-liquid interface that occur during photoelectrocatalytic water splitting. Neutron reflectometry and grazing incidence x-ray absorption spectroscopy were utilised to distinguish between the surface and bulk signals, with a surface sensitivity of 3 nm. Here we show, contrary to what is typically assumed, that the A cations are active sites that undergo oxidation at the surface as a consequence of the water splitting process. Whereas, the B cations undergo local disordering with the valence state remaining unchanged. This surface modification reduces the overall water splitting efficiency, but is suppressed when the oxynitride thin films are decorated with a co-catalyst. With this example we present the possibilities of surface sensitive studies using techniques capable of operando measurements in water, opening up new opportunities for applications to other materials and for surface sensitive, operando studies of the water splitting process.

Hybrid semiconductor-ferromagnetic insulator heterostructures are interesting due to their tunable electronic transport, self-sustained stray field, and local proximitized magnetic exchange. In this work, we present lattice-matched hybrid epitaxy of semiconductor-ferromagnetic insulator InAs/EuS heterostructures and analyze the atomic-scale structure and their electronic and magnetic characteristics. The Fermi level at the InAs/EuS interface is found to be close to the InAs conduction band and in the band gap of EuS, thus preserving the semiconducting properties. Both neutron and X-ray reflectivity measurements show that the overall ferromagnetic component is mainly localized in the EuS thin film with a suppression of the Eu moment in the EuS layer nearest the InAs and magnetic moments outside the detection limits on the pure InAs side. This work presents a step toward realizing defect-free semiconductor-ferromagnetic insulator epitaxial hybrids for spin-lifted quantum and spintronic applications without external magnetic fields.

Li ion transport through thin (14-22 nm) amorphous silicon layers adjacent to lithium metal oxide layers (lithium niobate) was studied by in situ neutron reflectometry experiments and the control mechanism was determined. It was found that the interface between amorphous silicon and the oxide material does not hinder Li transport. It is restricted by Li diffusion in the silicon material. This finding based on in situ experiments confirms results obtained ex situ and destructively by secondary ion mass spectrometry (SIMS) depth profiling investigations. The Li permeabilities obtained from the present experiments are in agreement with those obtained from ex situ SIMS measurements showing similar activation enthalpies.