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Jacopo Stefano Pelli Cresi Francesco Carl Raja Znaiguia Helena Isern Francesco Benedetti Gabriele Gasperi Lucia Amidani Sergio Valeri Federico Boscherini Paola Luches 《Advanced Materials Interfaces》2020,7(18)
To optimize the catalytic functionality of cerium oxide it is important to understand the structural modifications associated with reduction and the role of the proximity of metals, which are often coupled with the oxide in the applications. For this purpose, the evolution of the short‐ and long‐range structure of cerium oxide ultrathin epitaxial films and nanostructures supported on Pt(111) is investigated using X‐ray absorption spectroscopy at the Ce L3 edge and surface X‐ray diffraction, during reduction by thermal treatments in vacuum. In epitaxial nanoislands reduction is associated with a contraction of the Ce–O distance and with the appearance of Ce Pt bonds. The formation of a phase with a (2 × 2) periodicity after a thermal treatment at 1023 K is ascribed to the formation of a Pt5Ce alloy. Films of 3 nm thickness do not show, on average, significant structural modifications with the same thermal treatment, consistent with the hypothesis that the reduction involves only the topmost surface layers and it does not influence significantly the bulk structure of the material. This study demonstrates a strong interaction between cerium oxide and platinum, which has implications for the reactivity and stability of catalysts based on metals combined with reducible oxides. 相似文献
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Alex Frano Eva Benckiser Yi Lu Meng Wu Miguel Castro‐Colin Manfred Reehuis Alexander V. Boris Eric Detemple Wilfried Sigle Peter van Aken Georg Cristiani Gennady Logvenov Hanns‐Ulrich Habermeier Peter Wochner Bernhard Keimer Vladimir Hinkov 《Advanced materials (Deerfield Beach, Fla.)》2014,26(2):258-262
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In crystalline materials, the presence of surfaces or interfaces gives rise to crystal truncation rods (CTRs) in their X‐ray diffraction patterns. While structural properties related to the bulk of a crystal are contained in the intensity and position of Bragg peaks in X‐ray diffraction, CTRs carry detailed information about the atomic structure at the interface. Developments in synchrotron X‐ray sources, instrumentation, and analysis procedures have made CTR measurements into extremely powerful tools to study atomic reconstructions and relaxations occurring in a wide variety of interfacial systems, with relevance to chemical and electronic functionalities. In this review, an overview of the use of CTRs in the study of atomic structure at interfaces is provided. The basic theory, measurement, and analysis of CTRs are covered and applications from the literature are highlighted. Illustrative examples include studies of complex oxide thin films and multilayers. 相似文献
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Wenjing Li Iuliia Bykova Shilei Zhang Guoqiang Yu Riccardo Tomasello Mario Carpentieri Yizhou Liu Yao Guang Joachim Grfe Markus Weigand David M. Burn Gerrit van der Laan Thorsten Hesjedal Zhengren Yan Jiafeng Feng Caihua Wan Jinwu Wei Xiao Wang Xiaomin Zhang Hongjun Xu Chenyang Guo Hongxiang Wei Giovanni Finocchio Xiufeng Han Gisela Schütz 《Advanced materials (Deerfield Beach, Fla.)》2019,31(14)
Room temperature magnetic skyrmions in magnetic multilayers are considered as information carriers for future spintronic applications. Currently, a detailed understanding of the skyrmion stabilization mechanisms is still lacking in these systems. To gain more insight, it is first and foremost essential to determine the full real‐space spin configuration. Here, two advanced X‐ray techniques are applied, based on magnetic circular dichroism, to investigate the spin textures of skyrmions in [Ta/CoFeB/MgO]n multilayers. First, by using ptychography, a high‐resolution diffraction imaging technique, the 2D out‐of‐plane spin profile of skyrmions with a spatial resolution of 10 nm is determined. Second, by performing circular dichroism in resonant elastic X‐ray scattering, it is demonstrated that the chirality of the magnetic structure undergoes a depth‐dependent evolution. This suggests that the skyrmion structure is a complex 3D structure rather than an identical planar texture throughout the layer stack. The analyses of the spin textures confirm the theoretical predictions that the dipole–dipole interactions together with the external magnetic field play an important role in stabilizing sub‐100 nm diameter skyrmions and the hybrid structure of the skyrmion domain wall. This combined X‐ray‐based approach opens the door for in‐depth studies of magnetic skyrmion systems, which allows for precise engineering of optimized skyrmion heterostructures. 相似文献
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Sebastian Macke Abdullah Radi Jorge E. Hamann‐Borrero Adriano Verna Martin Bluschke Sebastian Brück Eberhard Goering Ronny Sutarto Feizhou He Georg Cristiani Meng Wu Eva Benckiser Hanns‐Ulrich Habermeier Gennady Logvenov Nicolas Gauquelin Gianluigi A. Botton Adam P. Kajdos Susanne Stemmer George A. Sawatzky Maurits W. Haverkort Bernhard Keimer Vladimir Hinkov 《Advanced materials (Deerfield Beach, Fla.)》2014,26(38):6554-6559
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Raphaël Aeschlimann Philipp Scheiderer Michael Sing Sergio Valencia Jacobo Santamaria Chen Luo Hanjo Ryll Florin Radu Ralph Claessen Cinthia Piamonteze Manuel Bibes 《Advanced materials (Deerfield Beach, Fla.)》2018,30(29)
When ferromagnetic films become ultrathin, key properties such as the Curie temperature and the saturation magnetization are usually depressed. This effect is thoroughly investigated in magnetic oxides such as half‐metallic manganites, but much less in ferrimagnetic insulating perovskites such as rare‐earth titanates RTiO3, despite their appeal to design correlated 2D electron gases. Here, the magnetic properties of epitaxial DyTiO3 thin films are reported. While films thicker than about 50 nm show a bulk‐like response, at low thickness a surprising increase of the saturation magnetization is observed. This behavior is described using a classical model of a “dead layer” but assuming that this layer is actually “living,” that is, it responds to the magnetic field with a strong paramagnetic susceptibility. Through depth‐dependent X‐ray absorption and photoemission spectroscopy, it is shown that the “living‐dead layer” corresponds to surface regions where magnetic (S = 1/2) Ti3+ ions are replaced by nonmagnetic Ti4+ ions. Hysteresis cycles at the Dy M5 and Ti L3 edges indicate that the surface Ti4+ ions decouple the Dy3+ ions, thus unleashing their strong paramagnetic response. Finally, it is shown how capping the DyTiO3 film can help increase the Ti3+ content near the surface and thus recover a better ferrimagnetic behavior. 相似文献
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Ashok Bera Weinan Lin Yingbang Yao Junfeng Ding James Lourembam Tom Wu 《Small (Weinheim an der Bergstrasse, Germany)》2016,12(6):802-809
Integrating nanomaterials with different dimensionalities and properties is a versatile approach toward realizing new functionalities in advanced devices. Here, a novel diode‐type heterostructure is reported consisting of 1D semiconducting ZnO nanorods and 2D metallic LaAlO3–SrTiO3 interface. Tunable insulator‐to‐metal transitions, absent in the individual components, are observed as a result of the competing temperature‐dependent conduction mechanisms. Detailed transport analysis reveals direct tunneling at low bias, Fowler–Nordheim tunneling at high forward bias, and Zener breakdown at high reverse bias. Our results highlight the rich electronic properties of such artificial diodes with hybrid dimensionalities, and the design principle may be generalized to other nanomaterials. 相似文献
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Diogo Castro Vaz Anke Sander Hiroshi Naganuma Eric Jacquet Jacobo Santamaria Agnès Barthélémy Manuel Bibes 《Advanced materials (Deerfield Beach, Fla.)》2017,29(28)
The quasi 2D electron system (q2DES) that forms at the interface between LaAlO3 and SrTiO3 has attracted much attention from the oxide electronics community. One of its hallmark features is the existence of a critical LaAlO3 thickness of 4 unit‐cells (uc) for interfacial conductivity to emerge. In this paper, the chemical, electronic, and transport properties of LaAlO3/SrTiO3 samples capped with different metals grown in a system combining pulsed laser deposition, sputtering, and in situ X‐ray photoemission spectroscopy are investigated. The results show that for metals with low work function a q2DES forms at 1–2 uc of LaAlO3 and is accompanied by a partial oxidation of the metal, a phenomenon that affects the q2DES properties and triggers the formation of defects. In contrast, for noble metals, the critical thickness is increased above 4 uc. The results are discussed in terms of a hybrid mechanism that incorporates electrostatic and chemical effects. 相似文献
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《Advanced Materials Interfaces》2017,4(5)
In multiphase/multilayer solid electrolytes, the composition, reactivity, and structure of interfaces between materials and phases play a fundamental role for fast ion‐conduction. Here, the properties of buried interfaces in prototypical fast ion‐conducting LaF3/SrF2 epitaxial multilayers are investigated. Photoelectron spectroscopy—both with soft‐X and high‐energy photons—is applied to separate composition and reactivity of buried interfaces with respect to the outermost surface. X‐ray reflectivity, high‐energy electron diffraction, X‐ray diffraction, atomic force and transmission electron microscopies are used to study morphology, layer crystallinity, epitaxy relations, and buried interface structure. It is found that while the alternated layers present good crystallinity and high lattice matching, with formation of almost ideal sharp interfaces, buried interfaces show a sizeable reduction of the energy barrier for F vacancy formation with respect to bare materials. A density higher by a factor of six of fluorine vacancies is observed at buried interfaces in multilayers with respect to the bare materials. This is correlated to the formation of space charge regions, favoring ion conduction. The formation of F depleted La fluoride regions at interfaces is also promoted by annealing. This is associated to the increase of ion conductivity in annealed heterostructures reported in literature. 相似文献
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Gebhard J. Matt Ievgen Levchuk Judith Knüttel Johannes Dallmann Andres Osvet Mykhailo Sytnyk Xiaofeng Tang Jack Elia Rainer Hock Wolfgang Heiss Christoph J. Brabec 《Advanced Materials Interfaces》2020,7(4)
Here the fabrication of an inorganic metal‐halide perovskite CsPbBr3 based X‐ray detector is reported utilizing a simple, scalable, and cost‐sensitive melt processing directly on substrate of any size. X‐ray diffraction analysis on the several 100 mm thick melt processed films confirms crystalline domains in the cm2 range. The CsPbBr3 film features a resistance of 8.5 GΩ cm and a hole mobility of 18 cm2 V−1 s−1. An X‐ray to current conversion rate of 1450 µC Gyair−1 cm−2 at an electric field of 1.2 × 104 V cm−1 and a detection limit in the sub µGyair s−1 regime is demonstrated. The high crystallinity and chemical purity of the melt processed CsPbBr3 films are suggested to be responsible for a performance which is on par to current state‐of‐the‐art Cd(Zn)Te based X‐ray detector technology. 相似文献
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Qinfen Gu Günter Krauss Walter Steurer 《Advanced materials (Deerfield Beach, Fla.)》2008,20(19):3620-3626
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Hua Zhou Ahmet Uysal Daniela M. Anjos Yu Cai Steven H. Overbury Matthew Neurock John K. McDonough Yury Gogotsi Paul Fenter 《Advanced Materials Interfaces》2015,2(17)
The noncovalent functionalization of graphene by small molecule aromatic adsorbates, phenanthrenequinone (PQ), is investigated systematically by combining electrochemical characterization, high‐resolution interfacial X‐ray scattering, and ab initio density functional theory calculations. The findings in this study reveal that while PQ deposited on pristine graphene is unstable to electrochemical cycling, the prior introduction of defects and oxygen functionality (hydroxyl and epoxide groups) to the basal plane by exposure to atomic radicals (i.e., oxygen plasma) effectively stabilizes its noncovalent functionalization by PQ adsorption. The structure of adsorbed PQ molecules resembles the graphene layer stacking and is further stabilized by hydrogen bonding with terminal hydroxyl groups that form at defect sites within the graphene basal plane. The stabilized PQ/graphene interface demonstrates persistent redox activity associated with proton‐coupled‐electron‐transfer reactions. The resultant PQ adsorbed structure is essentially independent of electrochemical potentials. These results highlight a facile approach to enhance functionalities of the otherwise chemically inert graphene using noncovalent interactions. 相似文献
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利用同步辐射Ｘ射线对Ｃｒ／ＳｉＯ２系统进行了反射率测量。得到了信噪比非常好的反射率曲线，通过对实验数据进行傅立叶变换和最小二乘法拟合得到了Ｃｒ膜的厚度经及Ｃｒ膜与ＳｉＯ２衬底界面的粗糙度。结果表明，该方法对精确测定界面的粗糙度非常有效。 相似文献
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《Advanced Materials Interfaces》2018,5(6)
It is shown that magnetite nanoparticles (MagNPs) grafted with polyethylene glycol (PEG) self‐assemble and short‐range‐order as 2D films at surfaces of aqueous suspensions by manipulating salt concentrations. Synchrotron X‐ray reflectivity and grazing‐incidence small angle X‐ray scattering studies reveal that K2CO3 induces the migration of the PEG‐MagNPs to the liquid/vapor interface to form a Gibbs layer of monoparticle in thickness. As the salt concentration and/or nanoparticle concentration increase, the surface‐adsorbed nanoparticles become more organized. And further increase in salt concentration leads to the growth of an additional incomplete nanoparticle layer contiguous to the first one at the vapor/liquid interface that remains intact. 相似文献
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Fei Jiang Wallace C. H. Choy Xinchen Li Di Zhang Jiaqi Cheng 《Advanced materials (Deerfield Beach, Fla.)》2015,27(18):2930-2937