Neutron Reflectometry Measurements Research Articles

Diffusion in Organic Film Stacks Containing Solution-Processed Phosphorescent Poly(dendrimer) Dopants.

Efficient organic light-emitting diodes (OLEDs) consist of an emissive layer comprising a blend of a light-emitting and host material in contact with one or more charge transporting layers. The distribution of the active material in the guest-host emissive layer blend and the changes that may occur upon thermal annealing are two important factors in determining the stability and efficiency of OLEDs. We have combined neutron reflectometry and photoluminescence measurements to investigate the structures of films comprising an emissive layer containing a phosphorescent poly(dendrimer) material blended with 4,4'-N,N'-di(carbazolyl)biphenyl. This combination has been shown to give rise to highly efficient OLEDs. Here, we show that the emissive poly(dendrimer) material was not uniformly distributed in the host, but formed a concentration gradient within the emissive layer. Upon heating, the adjacent electron transport layer was found to intermix with the emissive layer, accompanied by changes in the material distribution in the emissive layer. The intermixing of the materials led to a decrease in the photoluminescence from the poly(dendrimer) within the film. The decrease in the photoluminescence was ascribed to an increase in interchromophore interactions that could arise from a conformational change of the poly(dendrimer) or phase separation leading to aggregation. The results indicate that, while uniform mixing of the guest and host is not essential for efficiency, the thermal stabilities of both host and charge transport materials are important for device durability.

Surface Pressure-Induced Interdiffused Structure Evidenced by Neutron Reflectometry in Cellulose Acetate/Polybutadiene Langmuir Films.

Binary blends of water-insoluble polymers are a versatile strategy to obtain nanostructured films at the air-water interface. However, there are few reported structural studies of such systems in the literature. Depending on the compatibility of the polymers and the role of the air-water interface, one can expect various morphologies. In that context, we probed Langmuir monolayers of cellulose acetate (CA), of deuterated and postoxidized polybutadiene (PBd) and three mixtures of CA/PBd at various concentrations by coupling surface pressure-area isotherms, Brewster angle microscopy (BAM), and neutron reflectometry at the air-water interface to determine their thermodynamic and structural properties. The homogeneity of the films in the vertical direction, averaged laterally over the spatial coherence length of the neutron beam (∼5 μm), was assessed by neutron reflectometry measurements using D2O/H2O subphases contrast-matched to the mixed films. At 5 mN/m, the whole mixed films can be described by a single slightly hydrated thin layer. However, at 15 mN/m, the fit of the reflectivity curves requires a two-layer model consisting of a CA/PBd blend layer in contact with the water, interdiffused with a PBd layer at the interface with air. At intermediate surface pressure (10 mN/m), the determined structure was between those obtained at 5 and 15 mN/m depending on film composition. This PBd enrichment at the air-film interface at high surface pressure, which leads to the PBd depletion in the blend monolayer at the water surface, is attributed to the hydrophobic character of this polymer compared with the predominantly hydrophilic CA.

Highly Swollen Adsorption Layer Formed by Polymeric Friction Modifier Providing Low Friction at Higher Temperature

To reduce friction, especially under high-temperature conditions, an oil-soluble polymeric friction modifier (polymeric FM) with a methacrylate backbone and hydroxyl groups has been developed. It was designed to have high adsorption performance and to increase in size when dissolved in base oil as the temperature is increased. To investigate the temperature dependence of the structural and tribological characteristics of the adsorbed layer formed on a metal surface by the polymeric FM, neutron reflectometry measurements and nano-to-macro tribological tests were conducted. The measurements revealed that the polymeric FM adsorbed efficiently on a Cu surface and formed a 6.0-nm-thick adsorbed layer at 23 °C. This adsorbed layer was highly swollen, and its thickness became about three times larger at 100 °C. Nanoscale friction tests using an atomic force microscope showed that the swollen-state adsorbed polymeric FM layer exhibited low-friction and surface-protection performance at 100 °C. Macroscale friction tests revealed the tribological behaviour of an adsorbed polymeric FM layer in elastohydrodynamic lubrication and mixed lubrication regimes. At higher temperatures, the increase in shear resistance due to the effect of thin-film lubrication was suppressed by the weaker segment–segment interaction, causing the boundary contact of the adsorbed polymeric FM layer to have low frictional properties on both ball and disc surfaces. The low-friction mechanism of the adsorbed polymeric FM layer at higher temperatures was justified by associating the temperature with the layer thickness.

Charge Effects Provide Ångström-Level Control of Lipid Bilayer Morphology on Titanium Dioxide Surfaces.

Interfaces between molecular organic architectures and oxidic substrates are a central feature of biosensors and applications of biomimetics in science and technology. For phospholipid bilayers, the large range of pH- and ionic strength-dependent surface charge densities adopted by titanium dioxide and other oxidic surfaces leads to a rich landscape of phenomena that provides exquisite control of membrane interactions with such substrates. Using neutron reflectometry measurements, we report sharp, reversible transitions that occur between closely surface-associated and weakly coupled states. We show that these states arise from a complex interplay of the tunable length scale of electrostatic interactions with the length scale arising from other forces that are independent of solution conditions. A generalized free energy potential, with its inputs only derived from established measurements of surface and bilayer properties, quantitatively describes these and previously reported observations concerning the unbinding of bilayers from supporting substrates.

PH dependent electrical properties of the inner- and outer- leaflets of biomimetic cell membranes

Composition and asymmetry of lipid membranes provide a means for regulation of trans-membrane permeability of ions and small molecules. The pH dependence of these processes plays an important role in the functioning and survival of cells. In this work, we study the pH dependence of membrane electrical resistance and capacitance using electrochemical impedance spectroscopy (EIS), surface plasmon resonance (SPR) and neutron reflectometry (NR) measurements of biomimetic tethered bilayer lipid membranes (tBLMs). tBLMs were prepared with single-component phospholipid compositions, as well as mixtures of phospholipids (phosphatidylcholine, phosphatidylserine, phosphatidylethanolamine, sphingomyelin and cholesterol) that mimic the inner- and outer- leaflets of plasma cell membranes. We found that all studied tBLMs have a resistance maximum at pHs near the pKas of the phospholipids. SPR and NR indicated that surface concentration of phospholipids and the thickness of the hydrophobic part of the membrane did not change versus pH. We postulate that these maxima are the result of protonation of the phosphate oxygen of the phospholipids and that hydronium ions play a major role in the conductance at pHs < pKas while sodium ions play the major role at pHs > pKas. An additional sharp resistance maximum of the PE tBLMs found at pH 5.9 and most likely represents the phosphatidylethanolamine’s isoelectric point. The data show the key roles of the characteristic parts of phospholipid molecules: terminal group (choline, carboxyl, amine), phosphate, glycerol and ester oxygens on the permeability and selectivity of ions through the membrane. The interactions between these groups lead to significant differences in the electrical properties of biomimetic models of inner- and outer- leaflets of the plasma cell membranes.

Quantum Disordered States: Quantum Disordered State of Magnetic Charges in Nanoengineered Honeycomb Lattice (Adv. Sci. 6/2021)

Magnetic charges on the vertices of a two‐dimensional artificial magnetic honeycomb lattice can manifest liquid‐like quantum mechanical disorderness via charge dynamics. In article number 2004103, Deepak K. Singh, Valeria Lauter, and co‐workers demonstrate the existence of massively degenerate paramagnetic ground states at low temperature that are not greatly affected by magnetic field application. Experimental evidence, obtained using neutron reflectometry measurements (white incident light pattern), are tantamount to the occurrence of a novel quantum disordered state of magnetic charges. (Image credit: Oak Ridge National Laboratory/Jill Hemman)

Exchange bias switching in an antiferromagnet/ferromagnet bilayer driven by spin–orbit torque

The electrical manipulation of magnetization and exchange bias in antiferromagnet/ferromagnet thin films could be of use in the development of the next generation of spintronic devices. Current-controlled magnetization switching can be driven by spin–orbit torques generated in an adjacent heavy-metal layer, but these structures are difficult to integrate with exchange bias switching and tunnelling magnetoresistance measurements. Here, we report the current-induced switching of the exchange bias field in a perpendicularly magnetized IrMn/CoFeB bilayer structure using a spin–orbit torque generated in the antiferromagnetic IrMn layer. By manipulating the current direction and amplitude, independent and repeatable switching of the magnetization and exchange bias field below the blocking temperature can be achieved. The critical current density for the exchange bias switching is found to be larger than that for CoFeB magnetization reversal. X-ray magnetic circular dichroism, polarized neutron reflectometry measurements and micromagnetic simulations show that a small net magnetization within the IrMn interface plays a crucial role in these phenomena. The magnetization and exchange bias field in an IrMn/CoFeB bilayer can be independently switched using a current-controlled spin–orbit torque generated in the antiferromagnetic IrMn layer.

Adsorption of non-ionic surfactant and monoclonal antibody on siliconized surface studied by neutron reflectometry

The adsorption of monoclonal antibodies (mAbs) on hydrophobic surfaces is known to cause protein aggregation and degradation. Therefore, surfactants, such as Poloxamer 188, are widely used in therapeutic formulations to stabilize mAbs and protect mAbs from interacting with liquid-solid interfaces. Here, the adsorption of Poloxamer 188, one mAb and their competitive adsorption on a model hydrophobic siliconized surface is investigated with neutron scattering coupled with contrast variation to determine the molecular structure of adsorbed layers for each case. Small angle neutron scattering measurements of the affinity of Poloxamer 188 to this mAb indicate that there is negligible binding at these solution conditions. Neutron reflectometry measurements of the mAb show irreversible adsorption on the siliconized surface, which cannot be washed off with neat buffer. Poloxamer 188 can be adsorbed on the surface already occupied by mAb, which enables partial removal of some adsorbed mAb by washing with buffer. The adsorption of the surfactant introduces significant conformational changes for mAb molecules that remain on the surface. In contrast, if the siliconized surface is first saturated with the surfactant, no adsorption of mAb is observed. Competitive adsorption of mAb and Poloxamer 188 from solution leads to a surface dominantly occupied with surfactant molecules, whereas only a minor amount of mAb absorbs. These findings clearly indicate that Poloxamer 188 can protect against mAb adsorption as well as modify the adsorbed conformation of previously adsorbed mAb.

Manipulation of Coupling and Magnon Transport in Magnetic Metal-Insulator Hybrid Structures

Ferromagnetic metals and insulators are widely used for generation, control and detection of magnon spin signals. Most magnonic structures are based primarily on either magnetic insulators or ferromagnetic metals, while heterostructures integrating both of them are less explored. Here, by introducing a Pt/yttrium iron garnet (YIG)/permalloy (Py) hybrid structure grown on Si substrate, we studied the magnetic coupling and magnon transmission across the interface of the two magnetic layers. We found that within this structure, Py and YIG exhibit an antiferromagnetic coupling field as strong as 150 mT, as evidenced by both the vibrating-sample magnetometry and polarized neutron reflectometry measurements. By controlling individual layer thicknesses and external fields, we realize parallel and antiparallel magnetization configurations, which are further utilized to control the magnon current transmission. We show that a magnon spin valve with an ON/OFF ratio of ~130% can be realized out of this multilayer structure at room temperature through both spin pumping and spin Seebeck effect experiments. Thanks to the efficient control of magnon current and the compatibility with Si technology, the Pt/YIG/Py hybrid structure could potentially find applications in magnon-based logic and memory devices.

Unusual anomalous Hall effect in perpendicularly magnetized YIG films with a small Gilbert damping constant

The ${\mathrm{Y}}_{3}\mathrm{F}{\mathrm{e}}_{5}{\mathrm{O}}_{12}$ (YIG) films with perpendicular magnetic anisotropy (PMA) have recently attracted a great deal of attention for spintronics applications. Here, we report the induced PMA in the YIG films grown on $(\mathrm{G}{\mathrm{d}}_{2.6}\mathrm{C}{\mathrm{a}}_{0.4})(\mathrm{G}{\mathrm{a}}_{4.1}\mathrm{M}{\mathrm{g}}_{0.25}\mathrm{Z}{\mathrm{r}}_{0.65}){\mathrm{O}}_{12}$ (SGGG) substrates by epitaxial strain without preprocessing. Reciprocal space mapping shows that the films are lattice matched to the substrates without strain relaxation. Through ferromagnetic resonance and polarized neutron reflectometry measurements, we find that these YIG films have an ultralow Gilbert damping constant ($\ensuremath{\alpha}l1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$) and a magnetic dead layer, which is negligible at the YIG/SGGG interfaces. Moreover, the transport behavior of Pt/YIG/SGGG films reveals an enhancement of spin mixing conductance and a large unusual anomalous Hall effect (UAHE) as compared with $\mathrm{Pt}/\mathrm{YIG}/\mathrm{G}{\mathrm{d}}_{3}\mathrm{G}{\mathrm{a}}_{5}{\mathrm{O}}_{12}$ (GGG) films. Although the UAHE in Pt/YIG/SGGG films show different characteristics with varying YIG thickness, they are all ascribed to the possible noncollinear magnetic order at the Pt/YIG interfaces induced by epitaxial strain.

Physically Based Modeling of PEMFC Cathode Catalyst Layers: Effective Microstructure and Ionomer Structure–Property Relationship Impacts

AbstractThis work presents a pseudo-two-dimensional proton exchange membrane fuel cell (PEMFC) model incorporating Nafion ionomer structure–property relationships in the cathode catalyst layer (CL) to capture and explain losses at low Pt loading. Structural data from neutron reflectometry and thin film Nafion conductivity measurements predict variations in the oxygen diffusion coefficient and ionic conductivity with changing CL ionomer thickness and Pt loading. By including these structure–property relationships, predicted polarization curves agree closely with previously published experimental data from cells with Pt loadings between 0.025 and 0.2 mg/cm2. Results demonstrate that structure–property relationships based on physically measurable ionomer and CL properties provide a feasible interpretation of PEMFC CL phenomena for a range of Pt loadings and help explain previously unaccounted-for losses at low Pt. Results also show that simulations must account for surface species coverage variations in order to properly capture the kinetic losses. Finally, results suggest that an increase in ionomer thickness surrounding the C/Pt surfaces may lead to improved cell performance due to improved ionic conductivity.

Grazing Incidence Neutron Spin Echo Study of Poly(N-isopropylacrylamide) Brushes

The structure and dynamic properties of poly(N-isopropylacrylamide) brushes at solid planar surfaces under good solvent conditions are studied. Polymer brushes with grafting densities in the concentrated and semidilute regime are prepared via surface-initiated atom transfer radical polymerization. The polymer brushes were removed from the substrates to determine the molar mass and molecular dispersity via size-exclusion chromatography to draw conclusions about the grafting density. The structure of the brushes was investigated with ellipsometry and neutron reflectometry measurements. We found an influence of the grafting density on the swelling properties of the poly(N-isopropylacrylamide) brushes. Furthermore, the brush dynamics at different neutron penetration depths was analyzed with neutron spin echo spectroscopy under grazing incidence. The evanescent intensity distribution was modeled with the BornAgain software package, which uses the distorted-wave Born approximation.

The reaction of oleic acid monolayers with gas-phase ozone at the air water interface: the effect of sub-phase viscosity, and inert secondary components.

Organic films that form on atmospheric particulate matter change the optical and cloud condensation nucleation properties of the particulate matter and consequently have implications for modern climate and climate models. The organic films are subject to attack from gas-phase oxidants present in ambient air. Here we revisit in greater detail the oxidation of a monolayer of oleic acid by gas-phase ozone at the air-water interface as this provides a model system for the oxidation reactions that occur at the air-water interface of aqueous atmospheric aerosol. Experiments were performed on monolayers of oleic acid at the air-liquid interface at atmospherically relevant ozone concentrations to investigate if the viscosity of the sub-phase influences the rate of the reaction and to determine the effect of the presence of a second component within the monolayer, stearic acid, which is generally considered to be non-reactive towards ozone, on the reaction kinetics as determined by neutron reflectometry measurements. Atmospheric aerosol can be extremely viscous. The kinetics of the reaction were found to be independent of the viscosity of the sub-phase below the monolayer over a range of moderate viscosities, , demonstrating no involvement of aqueous sub-phase oxidants in the rate determining step. The kinetics of oxidation of monolayers of pure oleic acid were found to depend on the surface coverage with different behaviour observed above and below a surface coverage of oleic acid of ∼1 × 1018 molecule m-2. Atmospheric aerosol are typically complex mixtures, and the presence of an additional compound in the monolayer that is inert to direct ozone oxidation, stearic acid, did not significantly change the reaction kinetics. It is demonstrated that oleic acid monolayers at the air-water interface do not leave any detectable material at the air-water interface, contradicting the previous work published in this journal which the authors now believe to be erroneous. The combined results presented here indicate that the kinetics, and thus the atmospheric chemical lifetime for unsaturated surface active materials at the air-water interface to loss by reaction with gas-phase ozone, can be considered to be independent of other materials present at either the air-water interface or in the aqueous sub-phase.

Revealing the interfacial nanostructure of a deep eutectic solvent at a solid electrode.

Deep eutectic solvents (DESs) are both green and sustainable, making them an increasingly attractive alternative to conventional solvents. One of their applications is the electrochemical deposition of metals that cannot be deposited from aqueous solution because of the limited electrochemical window of water. The electrodeposition process is influenced by the structure and dynamics of the solvent at the solid-liquid interface. Therefore,the nanoscale structure of the interface between a silicon substrate and deep eutectic solvent (choline chloride-ethylene glycol) was studied by neutron reflectometry (NR) and molecular dynamics (MD) simulations. It is not possible to model NR measurements of this system without simulating a dense DES layer at the solid-liquid interface. This study used an MD simulation trajectory to extract the density, thickness, and roughness of this DES layer. With this input, the model reproduces the reflectometry data at all measured H/D contrasts very well. The thickness of the layer does not change appreciably when applying charge or at higher temperatures. Further analysis revealed a reorganization of ions and reorientation of the choline cations in the interface layer when the electrodes are charged. These changes in ion orientation are not observed with the NR technique since they do not influence the neutron scattering length density profile due to the high number of ethylene glycol molecules at the interface. However, the agreement between measured neutron reflectometry data and model parameters obtained from MD simulations justified subnanoscale analysis of the MD trajectory and confirmed that these two complementary techniques can be successfully combined to reveal the solid/DES interface structure.

The magnetic interfacial properties of an exchange biased nanocrystalline Ni80Fe20/α-Fe2O3 bilayer studied by polarized neutron reflectometry and Monte Carlo simulation

The strength of exchange bias can be influenced by interface roughness and antiferromagnetic morphology. Here, we studied the interface profile of an exchange biased, nanocrystalline Ni80Fe20/α-Fe2O3 bilayer. Magnetometry determined the bilayer’s exchange bias is observed below a blocking temperature of 75 K. Polarized neutron reflectometry measurements revealed the Ni80Fe20 layer was fully saturated to yield a net-moment of 0.95 μB/atom, while the majority of the Fe2O3 layer exhibited zero net-magnetization with the exception of the interfacial region with an uncompensated moment between 0.5 and 1.0 μB/Fe2O3. Monte Carlo simulations of a ferromagnetic/antiferromagnetic bilayer incorporating a granular antiferromagnet indicate that an extrinsic uncompensated moment of ∼1.0 μB/Fe2O3 can arise from grain boundary disorder. The size of the modeled moment is equivalent to the experimental value, and comparable with previous calculations. Furthermore, unlike intrinsic uncompensated spins, it is found that the disorder-induced moment in the granular antiferromagnet is not destroyed by interface roughness.

Block Copolymers‐Based Nanoporous Thin Films with Tailored Morphology for Biomolecules Adsorption

AbstractThe adsorption of myoglobin (Mb) onto nanoporous thin films build up using block‐copolymers (BCPs) is analyzed. The nanoporous thin films, fabricated by exploiting self‐assembly of lamellar BCPs and the concept of sacrificial block, are characterized by a well‐defined morphology containing nanochannels of width ≈20 nm delimited by polystyrene (PS) domains, decorated with pendant poly(ethylene oxide) (PEO) chains. The adsorption of Mb onto the nanoporous material is studied by means of UV–visible spectroscopy, quartz crystal microbalance, and neutron reflectometry measurements. In order to determine the role of nanopores, experiments are also conducted by using supports made of nonporous PS thin films and nude glass slides. The results indicate that the BCP‐nanoporous material exhibits a remarkably higher adsorption capability than PS and glass. As PEO exhibits a low degree of protein adsorption, this result may be essentially attributed to the presence of the nanopores. The large surface area, the opened pore structure, and the trapping effect of the pores are the main factors determining the increased Mb adsorption capability of the BCP‐based support. Yet, the presence of PEO chains decorating the PS walls at porous surface does not prevent Mb biomolecules to establish good interactions with the support.

Characterization of YIG thin films and vacuum annealing effect by polarized neutron reflectometry and magnetotransport measurements

Nanometer-thick Y3Fe5O12 (YIG) films epitaxially grown on (111) Gd3Ga5O12 with a magnetic dead layer as thin as about 1.2 nm are quantified by polarized neutron reflectivity and magnetization measurements. Vacuum annealing on YIG at 300–400 °C leads to substantial reduction in the anomalous Hall effect, spin Hall magnetoresistance, and spin pumping in YIG/Pt bilayers but causes large enhancement in the spin Seebeck effect. The structural, static, and dynamic magnetic measurements show that the annealing has no discernible influence on the global oxidization states and saturation magnetization of YIG films but introduces subtle defects possibly in the form of oxygen vacancies. This study suggests that subtle defects in thin YIG films have multiple effects on the spin transport properties, and caution should be taken in annealing YIG in vacuum.

Mucin Thin Layers: A Model for Mucus-Covered Tissues.

The fate of macromolecules of biological or pharmacological interest that enter the mucus barrier is a current field of investigation. Studies of the interaction between the main constituent of mucus, mucins, and molecules involved in topical transmucoidal drug or gene delivery is a prerequisite for nanomedicine design. We studied the interaction of mucin with the bio-inspired arginine-derived amphoteric polymer d,l-ARGO7 by applying complementary techniques. Small angle X-ray scattering in bulk unveiled the formation of hundreds of nanometer-sized clusters, phase separated from the mucin mesh. Quartz microbalance with dissipation and neutron reflectometry measurements on thin mucin layers deposited on silica supports highlighted the occurrence of polymer interaction with mucin on the molecular scale. Rinsing procedures on both experimental set ups showed that interaction induces alteration of the deposited hydrogel. We succeeded in building up a new significant model for epithelial tissues covered by mucus, obtaining the deposition of a mucin layer 20 Å thick on the top of a glycolipid enriched phospholipid single membrane, suitable to be investigated by neutron reflectometry. The model is applicable to unveil the cross structural details of mucus-covered epithelia in interaction with macromolecules within the Å discreteness.

Assessing molecular simulation for the analysis of lipid monolayer reflectometry

Using molecular simulation to aid in the analysis of neutron reflectometry measurements is commonplace. However, reflectometry is a tool to probe large-scale structures, and therefore the use of all-atom simulation may be irrelevant. This work presents the first direct comparison between the reflectometry profiles obtained from different all-atom and coarse-grained molecular dynamics simulations. These are compared with a traditional model layer structure analysis method to determine the minimum simulation resolution required to accurately reproduce experimental data. We find that systematic limits reduce the efficacy of the MARTINI potential model, while the Berger united-atom and Slipids all-atom potential models agree similarly well with the experimental data. The model layer structure gives the best agreement, however, the higher resolution simulation-dependent methods produce an agreement that is comparable. Finally, we use the atomistic simulation to advise on possible improvements that may be offered to the model layer structures, creating a more realistic monolayer model. Usage: Electronic Supplementary Information (ESI) including all analysis/plotting scripts and figure files, allowing for a fully reproducible, and automated, analysis workflow for the work presented is available at https://github.com/arm61/sim_vs_trad (DOI: 10.5281/zenodo.3254719) under a CC BY-SA 4.0 license. Reduced experimental datasets are available at DOI: 10.15125/BATH-00586, under a CC-BY 4.0 license.

Lithium Ion Distribution in Intercalation Electrode/Liquid Electrolyte Interfaces Determined By in-Situ Neutron Reflectometry

Gaining a thorough understanding of electrochemical interfaces is critical for the development of next-generation energy storage/conversion devices with high energy density and long-life operation. Direct observation of structural changes provides invaluable information about charge transfer, ionic diffusion, and side reactions in electrochemical reaction processes. Neutron reflectometry is a powerful technique for gaining a nanoscopic understanding at solid/liquid interfaces as a function of the depth[22]. Neutrons are capable of prove electrochemical interfaces owing to the strong penetrating power through the substrate. In addition, lithium can be sensitively detected by neutron; because the scattering length of lithium is significant in comparison with other elements in the electrode for neutron, whereas it is small and almost invisible for X-ray. The depth profile of the neutron scattering length density (SLD) obtained by analyzing the reflectivity profile can reveal the distribution of diffusing ions at the interface. Previous studies on the electrode/electrolyte interfaces by neutron reflectometry have mainly focused on the electrode-side interface (surface structural changes and/or surface electrolyte interphases) [1]. There are no reports of neutron reflectometry being used for discussing the depth distribution at the liquid-electrolyte side. In this study, we analyzed the concentration gradient of ionic species from the layered rocksalt type cathodeto the organic electrolyte by in situneutron reflectometry. Epitaxial Lix M yOz(M= Mn, Co, Ni) film model electrodes with (104) and (001) orientations were fabricated on Nb:SrTiO3single crystals by pulsed laser deposition. In situ neutron reflectometry measurements were conducted on a time-of-flight reflectometer (J-PARC, BL16 SOFIA) with a Li counter electrode and deuterated carbonate-base electrolyte containing LiPF6 [2]. The neutron reflectometry analyses demonstrate that the lithium concentrations in the interfacejust after the cell-construction (prior to electrochemical cycling) which may be related to formation of electrical double layer. The interfacial structures changed with the cell voltages during the electrochemical cycling. We will discuss on the crucial structure-parameters which determine the stability and the reaction rate in the interfacial regions. The depth-profile of the lithium ion distribution could give insight into research directions for electrode materials with highly-functional interfaces.