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Epitaxial integration of transition-metal oxides with silicon brings a variety of functional properties to the well-established platform of electronic components. In this process, deoxidation and passivation of the silicon surface are one of the most important steps, which in our study were controlled by an ultra-thin layer of SrO and monitored by using transmission electron microscopy (TEM), electron energy-loss spectroscopy (EELS), synchrotron X-ray diffraction (XRD) and reflection high energy electron diffraction (RHEED) methods. Results revealed that an insufficient amount of SrO leads to uneven deoxidation of the silicon surface i.e. formation of pits and islands, whereas the composition of the as-formed heterostructure gradually changes from strontium silicide at the interface with silicon, to strontium silicate and SrO in the topmost layer. Epitaxial ordering of SrO, occurring simultaneously with silicon deoxidation, was observed. RHEED analysis has identified that SrO is epitaxially aligned with the (001) Si substrate both with SrO (001) and SrO (111) out-of-plane directions. This observation was discussed from the point of view of SrO desorption, SrO-induced deoxidation of the Si (001) surface and other interfacial reactions as well as structural ordering of deposited SrO. Results of the study present an important milestone in understanding subsequent epitaxial integration of functional oxides with silicon using SrO. This journal is

SiO2 constitutes one of the most widely used dielectric materials in the microelectronics, packaging, and optical industries. Therefore, the development of new processes to deposit SiO2 at low temp...

[EN] Epsilon iron oxide (ε-FeO) coatings on Si(100) substrates are obtained by an easy one-pot sol-gel recipe assisted by glycerol in an acid medium. Glycerol, given its small dimensions, enables the formation of ε-FeO nanoparticles with a size of a few nanometers and the highest purity is reached in coatings after a densification treatment at 960 °C. The structural and compositional evolution up to 1200 °C is studied by confocal Raman microscopy and X-ray absorption spectroscopy techniques, correlating the existing magnetic properties. We report a novel characterization method, which allows monitoring the evolution of the precursor micelles as well as the intermediate and final phases formed. Furthermore, the inherent industrial technology transfer of the sol-gel process is also demonstrated with the ε-FeO polymorph, impelling its application in the coatings form., This work has been supported by the Ministerio de Ciencia e Innovación (MCINN, Spain) through the projects PIE: 2021-60-E-030, PIE: 2010-6-OE-013, PID2019-104717RB-I00 (2020–2022), MAT2017-86540-C4-1-R, RTI2018-095856-B-C21 (2019–2021), RTI2018-097895-B-C43 and RTI2018-095303-A-C52. The authors are grateful to The ESRF (France), MCINN and Consejo Superior de Investigaciones Científicas (CSIC, Spain) for the provision of synchrotron radiation facilities and to the BM25-SpLine Staff for their valuable help. A.S.and A.M.-N acknowledge financial support from Comunidad de Madrid (Spain) for an “Atracción de Talento Investigador” Contract 2017-t2/IND5395 and 2018-T1/IND-10360, respectively

The formation of xerogels implies a sequence of hydrolysis and condensation reactions, which are intricate to analyze in heteromolecular sols. We analyze by probabilistic Montecarlo methods the development of hybrid organosilane–titania xerogels and illustrate how partial charges of the reacting molecules can help estimating relative probabilities for the condensation of the molecules. Since the condensation rate of Ti alkoxides is much higher than the corresponding rate of Si alkoxides (especially if bearing a non-hydrolizable group), by imposing a fast condensation process in agreement with low pH kinetics, the process leads to a surface segregation of the organosilane. The simulation results are compared with results of characterization of thin condensates of two different organosilanes within a titanium–isopropoxide matrix. Non-destructive in-depth profiles were obtained by hard x-ray photoelectron spectroscopy, which can resolve through estimation of Si and specific moieties of the organosilane molecules the progress of the condensation. These results are relevant for the generalization of chemo-functionalization processes by kinetic demixing of organosilanes, which have myriad applications in biomedicine and biotechnology.

[EN]In this work, we present a strategy for developing epitaxial incommensurate nanostructured Au/oxide heterostructures with tunable plasmonic response. Previously, high-quality single-phase and single-oriented α-FeO(0001) thin films were achieved, which have been used as a template for noble-metal epitaxial deposition. The complex systems have been grown by pulsed laser deposition on two different types of oxide substrates: α-AlO(0001) and SrTiO(111). A one-step procedure has been achieved tailoring the isolated character and the morphological features of Au nanostructures through the substrate temperature during Au growth, without altering the structural characteristics of the hematite layer that is identified as a single iron oxide phase. The epitaxial character and the lattice coupling of Au/oxide bilayers are mediated through the sort of oxide substrate. Single-oriented Au(111) islands are disposed with a rotation of 30° between their crystallographic axes and those of α-FeO(0001). The Au(111) and SrTiO(111) lattices are collinear, while a rotation of 30° happens with respect to the α-AlO(0001) lattice. The crystallographic domain size and crystalline order of the hematite structure and the Au nanostructured layer are dependent on the substrate type and the Au growth temperature, respectively. Besides, the functional character of the complex systems has been tested. The localized surface plasmons related to Au nanostructures are excited and controlled through the fabrication parameters, tuning the optical resonance with the degree of Au nanostructuring., This work was supported by the Ministerio Español de Ciencia, Innovación y Universidades (MCIU), and the Consejo Superior de Investigaciones Cientificas (CSIC) through the project PIE-2010 6 OE 013. J.L.-S. and E.E. acknowledge the FPI fellowship and the Torres Quevedo contract (ref: PTQ-14-07289). The ESRF, MCIU, and CSIC are acknowledged for the provision of synchrotron radiation facilities. The authors thank Dr M.A. García for the useful discussion about the plasmonic results and Carlos Beltrán for technical support during the experiments at the BM25 beamline at The ESRF.

In this work, the functional character of complex -Fe2O3(0001)/SrTiO3(111) and Au(111) islands/ -Fe2O3(0001)/SrTiO3(111) heterostructures has been proven as gas sensors at room temperature. Epitaxial Au islands and -Fe2O3 thin film are grown by pulsed laser deposition on SrTiO3(111) substrates. Intrinsic parameters such as the composition, particle size and epitaxial character are investigated for their influence on the gas sensing response. Both Au and -Fe2O3 layer show an island-type growth with an average particle size of 40 and 62 nm, respectively. The epitaxial and incommensurate growth is evidenced, confirming a rotation of 30 between the in-plane crystallographic axes of -Fe2O3(0001) structure and those of SrTiO3(111) substrate and between the in-plane crystallographic axes of Au(111) and those of -Fe2O3(0001) structure. -Fe2O3 is the only phase of iron oxide identified before and after its functionalization with Au nanoparticles. In addition, its structural characteristics are also preserved after Au deposition, with minor changes at short-range order. Conductance measurements of Au(111)/ -Fe2O3(0001)/SrTiO3(111) system show that the incorporation of epitaxial Au islands on top of the -Fe2O3(0001) layer induces an enhancement of the gas-sensing activity of around 25% under CO and 35% under CH4 gas exposure, in comparison to a bare -Fe2O3(0001) layer grown on SrTiO3(111) substrates. In addition, the response of the heterostructures to CO gas exposure is around 5–10% higher than to CH4 gas in each case. This work has been supported by the Ministerio Español de Ciencia e Innovación (MICINN) and the Consejo Superior de Investigaciones Cientificas (CSIC) through the projects PIE-2010-OE-013- 200014, PIE 2021-60-E-030 and RTI2018-095303-A-C52. The ESRF, MICINN and CSIC are acknowledged for the provision of synchrotron radiation facilities. A.S. acknowledges financial support from Comunidad de Madrid for an “Atracción de Talento Investigador” Contract (2017-t2/IND5395).

The electron inelastic mean free path (IMFP) is commonly used in surface analysis techniques such as X-ray photoelectron spectroscopy. Though numerous studies have been conducted in the quest to define the IMFP value, it is still substantiated mainly on the basis of calculations and extrapolations. Experimental methods such as elastic peak electron spectroscopy tend to rely on indirect measurements. The main disadvantage of current methods is that the signal to noise ratio decreases with the increase in layer thickness or as the electron energy decreases. The newly developed wide energy spectrum (WES) method previously published by our group allows the IMFP to be directly evaluated for different electron energies. It exploits the attenuated electron multiple inelastic collisions (MIC) peak counts to calculate mean electron energy loss, rather than use the signal-electron peaks. In contrast, currently accepted methods focus on the signal electron in the spectrum and disregard the information contained in the lower-energy electrons. In understanding how to exploit this information, WES enhanced the relevant data collection by using a wide energy region upper bounded by the signal electron energy and lower bounded by the peak MIC energy in the spectrum. In this work, we have markedly expanded the validity of the WES method by assessing the IMFP values of a low Z polymer and by using a different substrate to produce the photoelectrons. The experiment was performed at the Spanish CRG Beamline (SpLine) at the European Synchrotron Radiation Facility (ESRF). Herein we present our initial results. In addition, we improved both the raw-data analysis and the background reduction processes used in WES to obtain enhanced and more accurate results. The IMFP values of carbon and polycarbonate were evaluated and compared with those predicted by the NIST. Small differences notwithstanding, the reported IMFP were shown to be well within the uncertainty boundaries. This work shows that the electron IMFP can be evaluated in solids by directly measuring the electrons that pass-through samples of the solids of interest. For the first time, there is an orderly path to experimentally evaluate electron IMFP by using the WES method. The new method was established to address the lack of experimental IMFP values for low energy electrons in solid materials.

International audience; The functionalization of nanoparticles is nowadays a standard procedure for many applications. Carbon nanotubes are no exception, and their functionalization has become an important part of the research effort these past decades. Nevertheless, there is still a lack of knowledge concerning the efficiency of the grafting processes, and more specifically concerning the question of the competition between covalent and non-covalent grafting when functionalized for example with aromatic fluorescent molecules. In a previous article, we investigated the grafting of fluorescein isothiocyanate onto double-walled carbon nanotubes. In order to explore the influence of the geometry of the fluorophore on the efficiency of the grafting processes, this work investigated the grafting of a streptocyanine onto the same carbon nanotubes using a combination of X-ray photoelectron spectroscopy, inelastic neutron scattering spectroscopy and computational simulations. The selected streptocyanine presents a very different geometry compared to FITC. Nevertheless, we show that, as in the case of FITC, both covalent and non-covalent grafting occurred simultaneously and that a comparable fraction of the fluorophore remained simply adsorbed onto the DWNTs despite thorough washings, indicating that the geometry of the streptocyanine did not exhibit the expected influence on the grafting process efficiency.

We have grown epitaxial incommensurate α-Fe2O3 thin films on α-Al2O3(0001), SrTiO3(111), and LaAlO3(001) substrates, identifying hematite as single iron oxide phase stabilized. We demonstrate that a different lattice coupling behavior as a function of the selected oxide substrate mediates the epitaxial character. Single-oriented α-Fe2O3(0001) layers are obtained on α-Al2O3(0001) and SrTiO3(111) substrates, whereas on the LaAlO3(001) substrate, the hematite layer is found to grow along the r-plane to adapt its hexagonal lattice on the cubic lattice of the substrate, evidencing a single-oriented (1102) layer. In the film plane, crystallographic axes of α-Fe2O3(0001) are collinear with the α-Al2O3(0001) ones, while a rotation of 30° is found between those of α-Fe2O3(0001) and SrTiO3(111). On LaAlO3(001), α-Fe2O3(1102) adopts an in-plane orthorhombic structure rotated 45° respect to the substrate lattice. The crystallographic domain size and the crystalline order are dependent on the incommensurate lattice ...

SrTiO 3 is a widely used substrate for the epitaxial growth of complex systems. Nevertheless, in order to get good quality interface and avoid the formation of defects in the adsorbed layer it is essential to prepare the surface of the substrate prior to the deposition. Thermal and chemical treatments are mostly used to eliminate superficial contamination and improve the surface quality. However, there is a lack of information regarding the impact of these treatments on the formation of structural defects at the SrTiO 3 surface. In this work we present a detailed characterization of the SrTiO 3 surface for the different cleaning methods paying special attention to the formation of oxygen vacancies, large surface mosaicity and roughness. We prove that thermal treatment induces large surface roughness and that chemical etching produces important structural defects at the surface. Our results show that mechanical polishing provided the best compromise in terms of large surface domains, low roughness, absence of oxygen vacancies and absence of atomic structure modification, although with the presence of low level of contaminants at the SrTiO 3 surface.

In this work we analyze the role of the SiO2 layer in the functionality of Fe3O4/SiO2/Si heterostructures, which have been proved to present a strong potential for spin-based applications. Nevertheless, a complete control of the interfaces properties is fundamental for application. In this work, high quality heterostructures are fabricated avoiding chemical exchange and achieving good quality interfaces. The chemical interaction between the Fe3O4 and SiO2 layers during the heterostructures manufacture is deeply analyzed and its role on the transport, magnetic and magneto transport response is revealed. It is proven that during Fe3O4 deposition a competitive interplay happens between the catalytic action of Fe atoms, the transport of dissociated oxygen through SiO2 and the stabilization of Fe3O4. A defective silicon oxide layer is found to grow on top of the native SiO2 enabling the formation of single phase Fe3O4 layer. Such a defective layer and the granular character of the Fe3O4 determine the magnetic and transport response of the heterostructures. The present results prove that the defects in the SiO2 layer induce the switching of the MR sign, so that anomalous positive MR at RT exceeding 17% at 80 kOe is obtained in heterostructures with 19 nm thick magnetite layer, while conventional negative MR response is obtained for thicker films.

Author(s): Urdiroz, U; Muller, C; Gomez, A; Magaz, MT; Granados, D; Sanchez Agudo, M; Rubio-Zuazo, J; Castro, GR; Stan, C; Tamura, N; Padmore, HA; Cebollada, F; Palomares, FJ; McCord, J; Gonzalez, JM | Abstract: We report on the measurement of the local magnetization dynamics occurring, at units of GHz, in large aspect ratio stripes lithographed from reduced damping amorphous Fe80B20 films. The stripes were submitted to local anisotropy modifications by micrometric beam synchrotron X-ray irradiation. Our results include data on the dispersion relationships and group velocities corresponding to spin waves excited at both the non-irradiated and the irradiated regions. Whereas in the former case we observed standing spin waves with transverse-to-the stripe axis wave vector, in the latter one, for which the wave vector of the spin waves was parallel-to-the stripe axis, propagating spin waves were excited. In both regions, we measured the effective propagation distance of the spin waves, which resulted to be independent of the wave vector orientation. In the spin waves excited at the irradiated region, we also measured the decay time and effective damping coefficient, which was in good agreement with previously reported values obtained from FMR measurements in amorphous Fe80B20 continuous films. We show that the interaction of the non-irradiated and irradiated zones results, at the stripe transverse saturation remanence and under an exciting field frequency of 4 GHz, in the introduction of a π phase shift between the standing spin waves excited at both sides of the irradiated region. This result opens the possibility of using the local, transverse to the stripe axis, magnetic anisotropy easy axis induced by the X-ray irradiation as a crucial constituent of a zero-applied field spin wave phase-shifter.

The Pr-based cobaltate $\mathrm{P}{\mathrm{r}}_{0.5}\mathrm{C}{\mathrm{a}}_{0.5}\mathrm{Co}{\mathrm{O}}_{3}$ (PCCO) presents in bulk form a singular simultaneous valence and spin-state transition that turns the metallic state into insulator, and displays a large and ultrafast photoresponse in the insulating phase. Epitaxial thin films of PCCO have been grown by deposition on $\mathrm{LaAl}{\mathrm{O}}_{3}$(001) (LAO) substrate, chosen to minimize the mismatch with the film. The films grow epitaxially with two times the substrate periodicity $(2{a}_{0}\ifmmode\times\else\texttimes\fi{}2{a}_{0}\ifmmode\times\else\texttimes\fi{}2{a}_{0})$ and the long perovskite axis perpendicular to the surface. We report a reduction of the structural symmetry from Pnma (bulk) to $P{2}_{1}{2}_{1}{2}_{1}$ (film). The $P{2}_{1}{2}_{1}{2}_{1}$ symmetry revealed by synchrotron x ray remains at low temperatures. These PCCO films are metallic, and ferromagnetic below ${T}_{\mathrm{C}}=170\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, confirming the stabilization of excited $\mathrm{C}{\mathrm{o}}^{3+}$ spin states and the suppression of the concurrent Co spin-state, valence, and metal-insulator transitions. $Z$-contrast imaging and electron-energy-loss spectroscopy elemental maps reveal long-range ordered oxygen vacancy planes unexpectedly stacking parallel to the interface, in spite of the tensile character of the PCCO/LAO heterostructure. In contrast to the general tendency reported for strained $\mathrm{L}{\mathrm{a}}_{0.5}\mathrm{S}{\mathrm{r}}_{0.5}\mathrm{Co}{\mathrm{O}}_{3\ensuremath{-}\ensuremath{\delta}}$ (LSCO) films, we show that a nominal tensile strain can be also compatible with the presence of alternating O vacancy planes parallel to the interface, instead of perpendicular to it. That occurs thanks to the double cell of the film and the formation of the (1/2, 1/2, 1/2) superstructure studied in this work. These results expand the possibilities of controlling interfacial physical properties via engineering of ordered oxygen-defect structures in strongly correlated oxides.

Electron emission from thick polished samples of polycrystalline molybdenum (Mo) and single crystalline 〈111〉 silver (Ag) was measured with hard x-ray photoemission spectroscopy. Six different excitation x-ray energies were used, nominally 8.0, 11.0, 13.0, 15.0, 18.0, and 21.5 keV. Survey spectra were recorded with each excitation to a kinetic energy of at most 15 keV, often capturing the entire emission range. The Mo 1s core peak was measured. Detailed LMM Auger spectra of Mo show marked increases in intensity and altered shape when x-ray energy exceeds the Mo 1s binding energy. The Mo and Ag L-shell photoelectron peaks are measured at four x-ray energies up to 18 keV showing the transition from 2p3/2 to 2s photoionization dominance.

Highlights X-ray irradiation of amorphous stripes allows to stabilize a transverse 180o wall. An inhomogeneous resonance can be excited with a 180° phase-shift across the wall. That phase-shift can be exploited into the design of magnonic devices. We report on the induction, through X-ray irradiation, of local anisotropy modifications in amorphous Fe80B20 stripes prepared by laser lithography from 15 nm thick films deposited by pulsed laser ablation. Those anisotropy modifications, taking place in a zone having a dimension of 15 μm around the X-ray beam (2 µm width) incidence area center point, lead to an effective transverse-to-the-stripe long axis local magnetic easy axis that can be exploited to stably localize a 180° domain wall, in remanence after saturation with a transverse-to the stripe easy axis dc field. Upon stabilizing that wall it is possible to excite spatially inhomogeneous ferromagnetic resonances nearby the irradiated region (IR). The time dependencies of the magnetization precession at both sides of the IR exhibit a uniform phase shift of 180° over distances of the order of 20 μm from the stabilized domain wall. This work has been developed with funds corresponding to project MAT2016-80394-R financed by the Spanish Research Agency (AEI). We also acknowledge the Spanish Ministerio de Ciencia e Innovaci ' on and Consejo Superior de Investigaciones Cientificas for financial support and for provision of synchrotron radiation at beamline BM25-SpLine (ESRF). This research used resources of the Advanced Light Source, a DOE Office of Science User Facility under contract no. DE-AC02-05CH11231. FC and JMG would like to dedicate this work to the memory of Dr. Dominique Givord with gratitude for the many things they were able to learn from him Peerreview

Scalable fabrication of magnetic 2D materials and heterostructures constitutes a crucial step for scaling down current spintronic devices and the development of novel spintronic applications. Here, we report on van der Waals (vdW) epitaxy of the layered magnetic metal Fe3GeTe2 (FGT) - a 2D crystal with highly tunable properties and a high prospect for room temperature ferromagnetism (FM) - directly on graphene by employing molecular beam epitaxy. Morphological and structural characterization confirmed the realization of large-area, continuous FGT/graphene heterostructure films with stable interfaces and good crystalline quality. Furthermore, magneto-transport and x-ray magnetic circular dichroism investigations confirmed a robust out-of-plane FM in the layers, comparable to state-of-the-art exfoliated flakes from bulk crystals. These results are highly relevant for further research on wafer-scale growth of vdW heterostructures combining FGT with other layered crystals such as transition metal dichalcogenides for the realization of multifunctional, atomically thin devices., They also acknowledge the provision of beamtime under the project HC-4068 at the European Synchrotron Radiation Facility (ESRF), located in Grenoble (France). ICN2 researchers acknowledge support from the European Union Horizon 2020 research and innovation programme under Grant Agreement No. 881603 (Graphene Flagship).

Single-phase and single-oriented epitaxial Cr2O3 thin film has been grown on SrTiO3 (1 1 1) substrate for the first time. The morphology, epitaxial growth mode and oxygen stoichiometry of the obtained film have been investigated by AFM, XRR, XRD and XPS, and compared to thin film grown on alfa-Al2O3 under equivalent conditions. The Cr2O3/SrTiO3 system presents a non-coincidence growth based on in&#-plane rotation of 30° of the Cr2O3 layer respect to the underlying SrTiO3 (1 1 1) substrate, while a coincidence growth based on axis-on-axis coupling is present for Cr2O3-Al2O3. However, in both cases an in-plane compression occurs in order to match the layer and substrate lattices. The formation of punctual defects in the form of oxygen vacancies have been observed by XPS for the layer grown on alfa-Al2O3, being the main mechanism for strain alleviation (4%). However, the 18 nm thick layer grown on SrTiO3 presents stoichiometric oxygen content maintaining an epitaxial strain (1.6%) accumulated on the lattice. Both epitaxial Cr2O3 layers show soft ferromagnetic response with coercive fields of 60 Oe and 90 Oe for the layer grown on SrTiO3 and alfa-Al2O3, respectively. The ESRF, MCIU and CSIC are acknowledged for the provision of synchrotron radiation facilities under Project No. PIE 2010-6-OE-013. This work has received financial support from Ministerio de Economía y Competitividad (Spain) under Project No. MAT2017-82970-C2-R and MAT2017-82970-C2-2-R. The microscopy works was conducted in the Laboratorio de Microscopías Avanzadas (LMA) at Instituto de Nanociencia de Aragón (INA)-Universidad de Zaragoza. The authors acknowledge the LMA-INA for offering access to their instruments and expertise. A. Prados would like to acknowledge the postdoctoral fellowship granted by Comunidad de Madrid and the European Union [PEJD-2016/IND-2233] and the use of facilities of Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM-UPM).

[EN] The composition of the active layer of a benchmark functional glass/ITO/[P3HT:PCBM][1.1:1]/Al organic solar cell has been studied by neutron reflectometry (NR) and hard X-ray photoelectron spectroscopy (HAXPES). Thermal annealing was performed in several steps and NR and HAXPES were recorded for every temperature. By fitting the NR results to a model composed of several layers, the scattering length density (SLD) distribution through the sample was obtained, and from this SLD profile, the evolution of the composition of the active layer as a function of temperature was established. For the outer layers, HAXPES results confirm the composition evolution. The results show that PCBM tends to segregate reducing the initial concentration of PCBM in the central part of the active layer and increasing its concentration towards both interfaces. The effect of the Al electrode as studied by HAXPES on the nearest zone of the active layer (up to 50 nm) is to stabilize the P3HT depletion in this area, an effect which is not affected by thermal annealing., Helpful comment sare acknowledged to Andrew Nelson,developer of the“Motofit”softwarepackage.This work was supported by Project ENE2016-79282-C5-5-R funded by MINECO-Spain (including FEDERfunds) and Project 19882-GERM-15 funded by Fundación Séneca(Región de Murcia, Spain). We acknowledge Institute Laue Langevin(ILL) for beamtime allocation at D17, and Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC) and European Synchrotron Radiation Facility(ESRF) for be a mtime allocation at line BM-25.

Reversible structural transformations between perovskite (PV) ABO3−δ and brownmillerite (BM) ABO2.5 (A = Ca2+, Sr2+; B = Fe4+/3, Co4+/3+) oxides can be induced by topotactic oxygen exchange at moderate temperatures under reducing/oxidizing conditions. The combination of a large oxide-ion conduc-tivity and a small free energy difference between the 4+/3+ oxidation states of many 3d transition metal ions enables these topotactic transformations. Herein, it is demonstrated that the electric field produced by a voltage-biased atomic force microscopy tip can induce such transformation between PV SrFeO3−δ and BM SrFeO2.5 at room temperature and with sub-micrometer spatial resolution. Interestingly, the structural transformation is kept after the electric field is removed, allowing a nonvolatile control of the local chemical, electrical, optical, and magnetic properties. Thus, the results presented in this paper open the door for the fabrication of stable ionic-based devices through the electric field patterning of different crystallographic phases., This work has received financial support from Ministerio de Economía y Competitividad (Spain) under Project Nos. MAT2016-80762-R, MAT2017-82970-C2-R, and PGC2018-101334-A-C22, Xunta de Galicia (Centro singular de investigación de Galicia accreditation 2016-2019, ED431G/09), the European Union (European Regional Development Fund-ERDF), and the European Commission through the Horizon H2020 funding by H2020-MSCA-RISE-2016 under Project No. 734187-SPICOLOST. This project has received funding from the European’s Union Horizon 2020 research and innovation programme under Grant No. 823717-ESTEEM3.

A stable BiI3 monosheet has been grown for the first time on the (0001) surface of the topological insulator Bi2Se3 as confirmed by scanning tunnelling microscopy, surface X-ray diffraction, and X-ray photoemision spectroscopy. BiI3 is deposited by molecular beam epitaxy from the crystalline BiTeI precursor that undergoes decomposition sublimation. The key fragment of the bulk BiI3 structure, a 2 [I—Bi—I] layer of edge-sharing BiI6 octahedra, is preserved in the ultra-thin film limit, but exhibits large atomic relaxations. The stacking sequence of the trilayers and alternations of the Bi—I distances in the monosheet are the same as in the bulk BiI3 structure. Momentum resolved photoemission spectroscopy indicates a direct band gap of 1.2 eV. The Dirac surface state is completely destroyed and a new flat band appears in the band gap of the BiI3 film that could be interpreted as an interface state., This work is supported by the DFG through SPP 1666 (Topological Insulators) and ERANET Chemistry program. The authors thank Arthur Ernst for providing the DFT calculations of the relaxed BiI3 double-layer film. We thank F. Weiss for technical support. The authors thank the staff of the ESRF and Elettra for their help and hospitality during their visit in Grenoble and Trieste, and G. Zamborlini, M. Jugovac and V. Feyer (PGI-6) for assistance, in using the NanoESCA beamline.

The interaction of CoO with highly oriented pyrolytic graphite (HOPG) was studied using a set of complementary techniques. The morphology of the CoO thin film was determined using atomic force microscopy (AFM), whereas the electronic structure was investigated using X-ray absorption (XAS) and photoemission (PES) spectroscopies. The experimental spectra were analyzed using a configuration interaction CoO cluster model calculation. The early stages of growth are characterized by the formation of a CoO wetting layer at the CoO/HOPG interface. The electronic structure of the CoO wetting layer presents a clear 2D character, which is closer to the 2D HOPG substrate than to the 3D CoO bulk. This character of the wetting layer explains the posterior formation of CoO islands and excludes the alternative layer by layer growth mode. Further, the interaction between the CoO wetting layer and the outermost graphite layer favors the oxidation of the HOPG substrate which can be controlled by the thickness of the deposited CoO overlayer, This investigation has been funded by the MINECO of Spain through the FIS2015-67367-C2-1-P project and by the Comunidad de Madrid through the NANOMAGCOSTCM-P2018/NMT4321 project. Authors R.J.O.M and M.A. thank the financial support of CNPq-Brazil. Funding from the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement n.°312284 is acknowledged

Among the electrodes for Li‐ion batteries, Li4Ti5O12 (LTO) stands out as anode owing to its stability and safety, in part ascribed to its low surface reactivity. However, the overlayer formation on the LTO surface upon electrochemical cycling is reported in recent years; a rough surface layer of electrochemically inactive α‐Li2TiO3 on top of the LTO (111) surface is suggested on the grounds of scanning probe techniques and theoretical ab initio calculations which would negatively strike on the battery performance. Hence the investigation of the LTO surface evolution is key to achieve more stable and safer Li‐ion batteries. LTO (111) thin film electrodes are used as model system where a variety of surface specific characterization techniques are applied to unveil the surface behavior of LTO in Li‐ion batteries. In contrast with previous studies, with the help of high‐resolution transmission electron microscopy and synchrotron‐based surface X‐ray diffraction, α‐Li2TiO3 is found to be a surface preparation product. Of special importance is the use of high‐resolution electron backscatter diffraction to report an increase on the LTO surface strain upon electrochemical cycling which can have a critical effect in long cycling performance of LTO that is always considered a zero‐strain material.

Polished single crystal gold was analyzed using hard x-ray photoemission at six different x-ray energies, nominally 8.0, 11, 13, 15, 18, and 22 keV. Survey spectra were recorded with each excitation to a maximum kinetic energy of 15 keV.

The rising interest shown for adaptable electronics and brain-inspired neuromorphic hardware increases the need for new device architectures and functional materials to build such devices. The rational design of these memory components also benefits the comprehension and thus the control over the microscopic mechanisms at the origin of memristivity. In oxide-based valence-change memories, the control of the oxygen drift and diffusion kinetics is a key aspect in obtaining the gradual analog-type change in resistance required for artificial synapse applications. However, only a few devices are designed with this in mind, as they are commonly built around ionic insulating active materials. This shortcoming is addressed by using a mixed ionic–electronic conductor as functional memristive material. This work demonstrates how the oxygen content in La2NiO4+δ (L2NO4), tuned through post-annealing treatments, has a critical influence on the memory characteristics of L2NO4-based memristive devices. The presence of interstitial oxygen point defects in L2NO4 affects both its structure and electrical properties. High oxygen stoichiometry in the pristine state leads to an increased electrical conductivity, ultimately resulting in an improved memory window with highly multilevel, analog-type memory programing capabilities, desirable for analog computing and synaptic applications in particular. This work was partially supported by the LabEx Minos ANR-10-LABX-55-01 and by two ANR funded projects MicroSwitch (ANR-14-ACHN-0012) and Alps Memories (ANR-15-CE24-0018). The authors acknowledge the European Synchrotron Radiation Facility (ESRF), the Spanish Ministry of Science, Innovation and Universities (MCIU), and the Spanish National Research Council (CSIC) for provision of synchrotron radiation facilities and the authors thank beamline staff for assistance in using beamline CRG BM25-SpLine. E.S.-C., J.R.-Z., and G.R.C. thank the MCIU and the CSIC for financially supporting this research project and the beamline operation under grant no. PIE 2010-6-OE-013. K. Momma and F. Izumi are kindly acknowledged for creating the VESTA[34] software (3D visualization of crystallographic structure).

A systematic study of the iron–silicon interfaces formed upon preparation of (Fe/Si) multilayers has been performed by combination of modern and powerful techniques. Samples were prepared by thermal evaporation under ultrahigh vacuum onto a Si(1 0 0) substrate. The morphology of these films and their interfaces was studied by a combination of scanning transmission electron microscopy, X-ray reflectivity, angle resolved X-ray photoelectron spectroscopy and hard X-ray photoelectron spectroscopy. The Si-on-Fe interface thickness and roughness were determined to be 1.4(1) nm and 0.6(1) nm, respectively. Moreover, determination of the stable phases formed at both Fe-on-Si and Si-on-Fe interfaces was performed using conversion electron Mössbauer spectroscopy on multilayers with well separated Si-on-Fe and Fe-on-Si interfaces. It is shown that while a fraction of Fe remains as α-Fe, the rest has reacted with Si, forming the paramagnetic c-Fe1−xSi phase and a ferromagnetic Fe rich silicide (DO3 type phase). We conclude that the paramagnetic c-Fe1−xSi silicide sublayer is identical in both Si-on-Fe and Fe-on-Si interfaces, whereas an asymmetry is revealed in the composition of the ferromagnetic silicide sublayer., The financial support of the Spanish MINECOMAT2011-23791, the President of Russia Grant (NSh-1044.2012.2), RFFI Grant 13-02-01265, the Ministry of Education and Science of Russian Federation (14.604.21.0002 and 02G25.31.0043), Aragonese DGA-IMANA E34 (cofunded by Fondo Social Europeo) and that received from the European Union FEDER funds is acknowledged. L.B.R. acknowledges the Spanish MINECO FPU 2010 grant.

Chemical solution methods for thin-film deposition constitute an affordable alternative to high-vacuum physical technologies, like Sputtering, Pulsed Laser Deposition (PLD) or Molecular Beam Epitaxy (MBE). Particularly, chemical methods have proven to be very suitable for producing functional films over large areas, especially in the relatively thick range, from >100 nm to microns. Also, their versatile ability to synthesize different types of materials, i.e. carbides, silicides, pnictides, oxides or chalcogenides, makes them very attractive for a wide range of applications and studies. However, problems with surface/interface roughness, control of stoichiometry in multicationic or precisely-doped materials, and a lack of accurate control of the thickness in the thin limit range (

Themechanism of widely observed intermixing of wurtzite and zinc-blende crystal structures in InAs nanowire (NW) grown by selective area epitaxy (SAE) is studied. We demonstrate that the crystal structure in InAs NW grown by SAE can be controlled using basic growth parameters, and wurtzitelike InAs NWs are achieved.We link the polytypic InAs NWs SAE to the reconstruction of the growth front (111)B surface. Surface reconstruction study of InAs (111) substrate and the following homoepitaxy experiment suggest that (111) planar defect nucleation is related to the (1 × 1) reconstruction of InAs (111)B surface. In order to reveal it more clearly, a model is presented to correlate growth temperature and arsenic partial pressure with InAs NW crystal structure. This model considers the transition between (1 × 1) and (2 × 2) surface reconstructions in the frame of adatom atoms adsorption/desorption, and the polytypism is thus linked to reconstruction quantitatively. The experimental data fit well with the model, which highly suggests that surface reconstruction plays an important role in the polytypism phenomenon in InAs NWs SAE.https://doi.org/10.1103/PhysRevMaterials.1.074603

Using surface x-ray diffraction and scanning tunneling microscopy in combination with first-principles calculations, we have studied the geometric and electronic structure of Cs-deposited ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$(0001) surface kept at room temperature. Two samples were investigated: a single ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$ crystal, whose surface was Ar sputtered and then annealed at $\ensuremath{\sim}500{\phantom{\rule{0.16em}{0ex}}}^{\ensuremath{\circ}}\mathrm{C}$ for several minutes prior to Cs deposition, and a 13-nm-thick epitaxial ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$ film that was not subject to sputtering and was annealed only at $\ensuremath{\sim}350{\phantom{\rule{0.16em}{0ex}}}^{\ensuremath{\circ}}\mathrm{C}$. In the first case, a considerable fraction of Cs atoms occupy top layer Se atoms sites both on the terraces and along the upper step edges where they form one-dimensional-like structures parallel to the step. In the second case, Cs atoms occupy the $fcc$ hollow site positions. First-principles calculations reveal that Cs atoms prefer to occupy Se positions on the ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$(0001) surface only if vacancies are present, which might be created during the crystal growth or during the surface preparation process. Otherwise, Cs atoms prefer to be located in $fcc$ hollow sites in agreement with the experimental finding for the MBE-grown sample.

Advanced Materials Technologies, 4 (6), ISSN:2365-709X

The oxidation and corrosion of copper are fundamental issues studied for many decades due to their ubiquitous and transversal impact. However, the oxidation of copper used as catalyst for graphene synthesis has opened a singular problem not yet solved. Contradictory results are reported about the protecting or enhancing role of graphene in copper oxidation. We study short- and long-term oxidation of copper with different characteristics, such as oxygen content and morphology, with and without graphene, and in polycrystalline copper foils and almost totally textured (100) and (111) copper films on MgO and sapphire substrates, respectively. We propose a mechanism to explain the enhanced oxidation of polycrystalline copper originated by oxygen encapsulated by the graphene impermeable layer during graphene growth. The initial oxygen content and the existence of grain boundaries are the main factors that determine the relevance of this process. Graphene is shown to prevent oxidation from the atmosphere for any of the copper substrates but also promotes slow oxidation derived by the release of out-of-equilibrium encapsulated oxygen. The formation of bubbles after several months evidence this slow release. The occluded oxygen in graphene covered copper is demonstrated by comparing the oxygen to copper ratio at different depths using hard X-ray photoelectron spectroscopy for samples with and without graphene., Funding by the Spanish Ministerio de Economía y Competitividad (MINECO) under Projects MAT2015-65356-C3-1-R and MAT2012-37276-C03-01 and Comunidad de Madrid Excellence Network under Project S2013/MIT-2740 is acknowledged. We also acknowledge the MINECO for financial support and provision of synchrotron radiation facilities at BM25 SpLine The Spanish CRG Beamline at the ESRF. L.A-F. acknowledges a FPI grant (BES-2013-062759) from MINECO.

Zn/MnO batteries including an ionic liquid-based gel polymer electrolyte (IL-GPE) have been discharged or discharged and then recharged reaching different states of charge. The Zn electrodes used in these Zn/MnO batteries are studied by HAXPES and synchrotron XRD techniques. Besides, HAXPES measurements are compared with the results obtained by a conventional XPS. Formation of Zn(OH) and ZnO is found in intermediate states of charge during charging and discharging. However, only ZnO is observed in the anode when a full discharging was carried out. Conversely, an entire charging process produces a complete reduction of all Zn species to metallic Zn. In addition, various techniques have confirmed the entrance of Triflate anions and NMP solvent molecules in the electrode, accompanying the Zn cations movement during the charging., The authors thank the financial support from the Spanish Ministerio de Economía y Competitividad (Ref. ENE2013-48816-C5-3-R and ENE2016-79282-C5-5-R) including FEDER funds and provision of synchrotron radiation facilities at ESRF BM25B line. A.U. thanks F. Séneca (Región de Murcia, Ref: 19882-GERM-15).

In this contribution, we present results of a non-destructive in-depth analysis of concentration of chemical components at buried interfaces on Ge-based CMOS by means of hard X-ray photoelectron spectroscopy (HAXPES) and low angle X-ray reflectivity (XRR). Two samples composed of a Ge/Si/SiO 2 /HfO 2 /TiN stack, with layer and interlayer thicknesses of 2500, 0.9, 0.5, 4.9, 3.4 nm and 2500, 0.7, 1, 5.8, 3 nm have been studied. The use of electrons with kinetic energies from few eV up to 15 keV enables to tune the information depth being able to analyze the desired interface in a non-destructive way. XRR enables the determination of the exact layer thickness and density. The results suggest that the Si interlayer prevents the Ge oxidation. Depth profiles of the electronic structure have been obtained for both samples by following the evolution of the photoemission signal from the Hf 2p 3/2 core level as a function of the photoelectron kinetic energy. The depth profile of the electronic structure reveals the presence of a chemical shift of the Hf 2p 3/2 core level, which is related to an interfacial bonding state. Our results demonstrate the excellent capability of HAXPES to study buried interfaces in a non-destructive way.

We studied the Ni 2p core-level spectra of NiO using cluster model calculations and X-ray photoemission spectra. The calculations were performed for a NiO6, a NiO5, and a NiO6:NiO5 cluster, which allows studying the bulk, the surface, and the non-local effects in the spectra. The photoemission spectra were taken with soft (or hard) X-rays to enhance the surface (or bulk) contribution. The calculation shows that both surface and non-local-effects contribute to the shoulder in the experimental data. The photoemission spectra show that the relative intensity of the surface contribution decreases for Hard X-rays.

Vertical InAs nanowires (NWs) grown on a Si substrate are promising building-blocks for next generation vertical gate-all-around transistor fabrication. We investigate the initial stage of InAs NW selective area epitaxy (SAE) on a patterned Si (111) substrate with a focus on the interfacial structures. The direct epitaxy of InAs NWs on a clean Si (111) surface is found to be challenging. The yield of vertical InAs NWs is low, as the SAE is accompanied by high proportions of empty holes, inclined NWs, and irregular blocks. In contrast, it is improved when the NW contains gallium, and the yield of vertical InxGa1-xAs NWs increased with higher Ga content. Meanwhile, unintentional Ga surface contamination on a patterned Si substrate induces high yield vertical InAs NW SAE, which is attributed to a GaAs-like seeding layer formed at the InAs/Si interface. The role of Ga played in the III-V NW nucleation on Si is further discussed. It stabilizes the B-polarity on a non-polar Si (111) surface and enhances the nuc...

Some samples of raw blue pigments coming from an archaeological rescue mission in downtown Mexico City have been characterized using different techniques. The samples, some recovered as a part of a ritual offering, could be assigned to the late Aztec period (XVth century). The striking characteristic of these samples is that they seem to be raw pigments prior to any use in artworks, and it was possible to collect a few μg of pigment after manual grain selection under a microscopy monitoring. All pigments are made of indigo, an organic colorant locally known as anil or xiuhquilitl. The colorant is always found in combination with an inorganic matrix, studied by powder diffraction. In one case the mineral base is palygorskite, a rare clay mineral featuring micro-channels in its structure, well known as the main ingredient of the Maya blue pigment. However, other samples present the minerals sepiolite (a clay mineral of the palygorskite family) and calcite. Another sample contains barite, a mineral never reported in prehispanic paints. We present the results of characterization using high resolution powder diffraction recorded at the European Synchrotron Radiation Facility (BM25A, SpLine beamline) complemented with other techniques. All of them gave consistent results on the composition. A chemical test on resistance to acids was done, showing a high resistance for the palygorskite and eventually sepiolite compounds, in good agreement with the excellent resistance of the Maya blue.

The design of metallic hybrid systems for spintronics has been widely studied during the past decade, motivated by the promising technological applications of these materials. Nevertheless, the importance of preserving the native structure and properties of the interfaces is often ignored. Here, we present the fabrication of nanocrystalline Au (0 0 1) onto a single oriented Fe3O4 (0 0 1) thin film as a promising hybrid system to develop spintronic devices by growing Au over the Fe3O4 by using a simple one-pot Pulsed Laser Deposition (PLD) approach. The structural coupling between Au nanocrystals and Fe3O4 layer results in the development of an incommensurate structure based on a coincidence lattice of order 35, which preserves the intrinsic properties of the Au nanocrystals, the Fe3O4 matrix and the interface between them. The general strategy described in the present work preserves the structure and main intrinsic properties of the constituting materials, being a fundamental issue for the future development of spintronic devices., The authors are grateful to the SpLine staff for their valuable help and to the financial support from the Spanish MINECO and Consejo Superior de Investigaciones Cientificas under Grant Nos. MAT2011-23785, MAT2013-48009-C4-1-P and 20106OE013. Dr. F. Rubio-Marcos is also indebted to MINECO for a “Juan de la Cierva> contract (ref: JCI-2012-14521), which is co-financed with FEDER funds.

The crystallographic structure of La0.7Ca0.3MnO3 (LCMO) ultra-thin films grown on SrTiO3(0 0 1) has been investigated by surface X-ray diffraction (SXD) and the correlation between their transport and magnetic properties and crystallographic structure is discussed. LCMO thin films in a thickness range between 2.4 and 27 nm were grown by DC-sputtering on SrTiO3(0 0 1). We distinguish two different crystallographic structures associated to the 2.4 and 27 nm thin films, respectively. The 27 nm film structure corresponds to a tetragonal perovskite (space group Pbnm), as has been reported for bulk LCMO. For the 2.4 nm film the La/Ca ions are located at the regular position of an ideal perovskite and the MnO6 octahedrons are aligned along the c-axis. The MnO2 stacking layer (basal plane) is distorted and coplanar to the a–b crystallographic axis with an anti-correlation between octahedron layers. This observed distortion is not compatible with the Pbnm space group. The new phase, which cannot be excluded to coexist at the interface of thicker films, can be described, as an example, through an I4/mcm or Pbcn space group. Based on the observed structure, plausible models to explain their transport and magnetic behaviour are proposed. For the 2.4 nm film, an octahedron in-plane (basal plane) distortion induced by the substrate is observed. Thicker films behave structurally and magnetically as bulk-like materials.

We present structural, electronic, and morphological characterization of thin (7.5 nm, 9 unit cells) and ultrathin (1.7 nm, 2 unit cells) Fe3O4 layers grown on SrTiO3(001) by oxygen assisted molecular beam epitaxy (MBE) and pulsed laser deposition (PLD) methods. The analysis show single-phase single oriented (001) layers that grow forming a coincidence lattice of the order 13. Such an incommensurate growth is present for all the layers, independent of the evaporation method and layer thickness. The magnetite layers, which are strain-free, provide a sharp interface with the substrate. The films grown by the MBE method present negligible interaction with the substrate and smooth surfaces. The films grown by the PLD evaporation method present an expansion of the last atomic layer of the substrate and rough layer surface. However, the obtained structural domain size of 10 nm is identical for the layers grown by both evaporation techniques corresponding to the size of the coincidence lattice. We determine that the magnetic and transport properties inherent to the Fe3O4/ STO heterostructure are not related to the lattice strain but to the formation of antiphase boundary defects., The authors are grateful to the SpLine staff for their valuable help and for the financial support from the Spanish MINECO and Consejo Superior de Investigaciones Cientificas under Grant Nos. MAT2011-23785 and 20106OE013.

© 2015 Macmillan Publishers Limited. All rights reserved. A plethora of technological applications justify why titanium dioxide is probably the most studied oxide, and an optimal exploitation of its properties quite frequently requires a controlled modification of the surface. Low-energy ion bombardment is one of the most extended techniques for this purpose and has been recently used in titanium oxides, among other applications, to favour resistive switching mechanisms or to form transparent conductive layers. Surfaces modified in this way are frequently described as reduced and defective, with a high density of oxygen vacancies. Here we show, at variance with this view, that high ion doses on rutile titanium dioxide (110) induce its transformation into a nanometric and single-crystalline titanium monoxide (001) thin film with rocksalt structure. The discovery of this ability may pave the way to new technical applications of ion bombardment not previously reported, which can be used to fabricate heterostructures and interfaces.

AlN-based compounds are studied as potential candidate to be used as substrate in surface acoustic wave (SAW) devices. In this paper, we present a study of the acoustic waves phase velocity behavior of a Al x Ga 1− x N thin film set prepared by molecular beam epitaxy on Si(111) (0≤ x ≤1 covering the full x -range). This study has been carried out by Brillouin spectroscopy and shows a nearly linear compositional dependence in the full range of concentrations. The maximum value the phase velocity for waves traveling along the film plane directions (11 200 m s −1 ) is reached for AlN.

Monolithically integrating BaTiO3 on silicon substrates has attracted attention because of the wide spectrum of potential novel applications ranging from electronics to photonics. For optimal device performance, it is important to control the BaTiO3 domain orientation during thin film preparation. Here, we use molecular beam epitaxy to prepare crystalline BaTiO3 on Si(001) substrates using a SrTiO3 buffer layer. A systematic investigation is performed to understand how to control the BaTiO3 domain orientation through the thickness engineering of the SrTiO3 buffer layer and the BaTiO3 layer itself. This provides different possibilities for obtaining a given BaTiO3 orientation as desired for a specific device application.

Using surface x-ray diffraction in combination with ab initio calculations we have studied the atomic structure of ultra-thin ZnO films deposited on Fe(110). In contrast to expectation that ZnO adopts the “graphitic” hexagonal Boron-nitride structure to the Wurtzite (WZ) structure is observed. Its formation is related to oxygen impurities in Fe(110) hollow sites inducing an anisotropic charge redistribution within the film which is characterized by a metallic surface. Our results provide a deeper understanding of depolarization mechanisms in ultrathin polar films at the atomic scale., This work is supported by the DFG.

A set of gadolinium thin films was prepared over Si(100) substrates by DC-operated planar magnetron sputtering deposition. This paper reports a change in the film texture by changing the sputtering working Ar gas pressure. An X-ray study of their structural properties shows that films have (0002) and (1010) orientations. On the other hand, their elastic properties have been studied by Surface Brillouin Light Scattering spectroscopy that provides the velocity of the surface acoustic waves. A simulation that takes into account values of thin film density and elastic constants tensor identical to the corresponding for bulk gadolinium shows good agreement between theory and experiment for (0002)-textured samples. Nevertheless, (1010)-textured films seem to have slightly different values of the elastic constant.

This paper describes a combined structural analysis of the Zn-histidine complex, using two different and complementary techniques, X-ray absorption spectroscopy (XAS) and surface X-ray diffraction, paying special attention to the environmental conditions. The current procedure for investigating macromolecules consists of examining simple molecules that exhibit properties similar to those of the larger ones, whose functionality is totally related to the atomic structure. The detailed study of the bonding structure formed by zinc and histidine amino acids is motivated by the fact that this material serves as a model for metalloproteins, such as in metalloproteinase, acting as active sites in enzymatic or structural functions. For XAS modeling, Zn-histidine complexes were dissolved in several aqueous solutions, over a wide pH range. Correlations among the degree of protonation, the steric impediment, and the multiple combinations of the histidine amino acid have been found. For the diffraction study, high-quality crystals grown by the seeding method in a supersaturated solution have been studied, and the samples for the surface diffraction study were mounted on a cell specially designed for solid-liquid or solid-gas interface analysis. The surface structural model was built from XAS results. In both cases, the obtained structures are compared with the bulk one, showing atomic differences and highlighting the importance of the environment in which the complex is studied. © 2014 American Chemical Society., The financial support of the Consejo Superior de Investigaciones Cientifícas and Spanish Ministerio de Ciencia e Innovación (PI201060E013 and MAT2011-23758) is also acknowledged.

Diffusion and reaction of elements at the interfaces of nanostructured systems play an important role in controlling their physical and chemical properties for subsequent applications. (Fe/Si) nanolayers were prepared by thermal evaporation under ultrahigh vacuum onto a Si(100) substrate. A morphological characterization of these films was performed by combination of scanning transmission electron microscopy (STEM) and X-ray reflectivity (XRR). The compositional depth profile of the (Fe/Si) structures was obtained by angle resolved X-ray photoelectron spectroscopy (ARXPS) and hard X-ray photoelectron spectroscopy (HAXPES). Moreover, determination of the stable phases formed at the Si on Fe interfaces was performed using conversion electron Mössbauer spectroscopy. The Si/Fe interface thickness and roughness were determined to be 1.4 nm and 0.6 nm, respectively. A large fraction of the interface is composed of c-Fe1-xSi paramagnetic phase, though a minoritary ferromagnetic Fe rich silicide phase is also present., The financial support of the Spanish MINECO MAT2011-23791, the President of Russia Grant (NSh-1044.2012.2), RFFI grant 13-02-01265, the Ministry of Education and Science of Russian Federation, projects GK14.B37.21.1276 and GK16.740.11.0740, Aragonese DGA-IMANA E34 (cofunded by Fondo Social Europeo) and that received from the European Union FEDER funds are acknowledged. L. B. R. acknowledges the Spanish MINECO FPU 2010 grant.

The stacking modes of graphene oxide monolayers (GO) when forming thin films is a crucial aspect determining many properties especially those related with transport. Stacking, morphology and effects of thermal and chemical reduction are studied combining insitu synchrotron radiation diffraction and atomic force microscopy with simulations. The GO flakes mimic the substrate morphology and present an almost perfect stacking for few-layer films (2-10 layers) when in-plane flake size is large enough. The interlayer distance is found to be 1 nmirrespective of the film thickness and drastic discontinuities upon thermal annealing are observed between 100 and 200 -C. Moreover, the short GO-GO distance (0.38 nm) observed at temperatures (500 -C) where oxygen content is still high indicates that stacking is mainly governed by embedded water molecules. The large interlayer distance (0.76 nm) in chemically reduced films and its robustness against thermal annealing are due to the folding of the edges of the flakes occurring upon the elimination of the functional groups. The central part of the flakes remains extremely flat contrary to what occurs with thermal reduction. These structural defects induced by chemical and thermal reduction processes are very probably the most important limitations for electrical conductivity in GO based electrodes., X.D. acknowledges a FPI scholarship from Spanish MINECO and C.M. thanks financial support from the “Juan de la Cierva” postdoctoral program JCI-2011-08815. The research leading to these results has received funding from Spanish MINECO under projects MAT2012-37276-C03-01, MAT2011-27470-C02-02, CSD2009-00050 and CSD2009-00013 as well as from the European Union Seventh Framework Program under grant agreement n° 604391 “Graphene Flagship.”