Colossal Ionic Conductivity at Interfaces of Epitaxial ZrO2:Y2O3/SrTiO3 Heterostructures (original) (raw)
Related papers
Seeing oxygen disorder in YSZ/SrTiO 3 colossal ionic conductor heterostructures using EELS
The European Physical Journal Applied Physics, 2011
Colossal ionic conductivity was recently discovered in YSZ/SrTiO3 multilayers and was explained in terms of strain-and interface-enhanced disorder of the O sublattice. In the present paper we use a combination of scanning transmission electron microscopy and electron energy loss spectroscopy (EELS) and theoretical EELS simulations to confirm the presence of a disordered YSZ O sublattice in coherent YSZ/SrTiO3 multilayers. O K-edge fine structure simulated for the strained disordered O sublattice phase of YSZ possesses blurred-out features compared to that of ordered cubic bulk YSZ, and experimental EELS fine structure taken from the strained YSZ of coherent YSZ/SrTiO3 thin films is similarly blurred out. Elemental mapping is shown to be capable of resolving ordered YSZ O sublattices. Elemental mapping of O in the coherent YSZ/STO multilayers is presented in which the O sublattice is seen to be clearly resolved in the STO but blurred out in the YSZ, indicating it to be disordered. In addition, we present imaging and EELS results which show that strained regions exist at the incoherent interfaces of YSZ islands in STO with blurred out fine structure, suggesting these incoherent regions may also support high ionic conductivities. Recently, Cavallaro et al. reported electronic conductivities in samples of incoherent disconnected islands embedded in STO that are similar to the islands described herein. The presence of a region of O depleted STO at the interface with incoherent YSZ islands is revealed by EELS elemental mapping, implying the n-type doping of STO/YSZ nanocomposites with disconnected incoherent YSZ islands.
Non-periodicity of peak-to-peak distances in x-ray diffraction spectrums from perfect superlattices
Journal of Applied Physics, 2013
High mobility half-metallicity in the (LaMnO3)2/(SrTiO3)8 superlattice Appl. Phys. Lett. 102, 042401 (2013) Strain effects on magnetic characteristics of ultrathin La0.7Sr0.3MnO3 in epitaxial La0.7Sr0.3MnO3/BaTiO3 superlattices J. Appl. Phys. 112, 123919 (2012) Radiation tolerance characterization of dual band InAs/GaSb type-II strain-layer superlattice pBp detectors using 63 MeV protons Appl. Phys. Lett. 101, 251108 Nanostructured thermoelectric cobalt oxide by exfoliation/restacking route J. Appl. Phys. 112, 113705 (2012) Strain effect in PbTiO3/PbZr0.2Ti0.8O3 superlattices: From polydomain to monodomain structures X-ray diffraction investigations of type II InAs/GaSb superlattice on a GaSb(001) substrate are presented. The wide range of diffraction angles (2h/x scans) covering 002 and 004 reflections was examined at Petra III synchrotron. The angular region between 002 and 004 reflections was the most interesting part of the measured diffraction profile. In this region, a non-coincidence of superlattice satellite peaks belonging to these two reflections is observed. The multiple-beam dynamical diffraction approach was used for correct simulation of the observed diffraction profile.
Applied Surface Science, 2006
The investigation of nanostructured oxide thin films using high-resolution X-ray diffraction (XRD) is considered. Because of the small amount of matter deposited and significant defect densities, such oxide thin film structures can be considered as imperfect materials that require specific data acquisition and data analysis methods. Fast reciprocal space mapping is carried out using a diffractometer based on an 18 kW X-ray source, a four-reflection monochromator and a curved position sensitive detector. In order to extract quantitative information concerning the microstructure of the films, an approach is developed that combines a microscopic modelling of dimensional effects (crystallite or island shape, size and size distribution) with a phenomenological description of lattice disorder. Within this approach, simple analytical expressions or expressions implying a simple Fourier transform, can be derived for the XRD intensity distribution in the direction perpendicular to the film surface and parallel to it. Profiles exhibiting damped and/or broadened fringes and profiles exhibiting a two-component line shape can be simulated. Parameters of primary interest, such as the island thickness, thickness distribution function, island in-plane dimensions and the distribution function of the dimensions, the level of disorder, the disorder correlation length and the spatial distribution of disorder, can be extracted. The applicability of the model is illustrated with yttria stabilized zirconia films epitaxially grown on sapphire by sol-gel dip-coating. #
The SrTiO $ _3 $ displacive transition revisited by Coherent X-ray Diffraction
We present a Coherent X-ray Diffraction study of the antiferrodistortive displacive transition of SrTiO3, a prototypical example of a phase transition for which the critical fluctuations exhibit two length scales and two time scales. From the microbeam x-ray coherent diffraction patterns, we show that the broad (short-length scale) and the narrow (long-length scale) components can be spatially disentangled, due to 100 µm-scale spatial variations of the latter. Moreover, both components exhibit a speckle pattern, which is static on a ∼10 mn time-scale. This gives evidence that the narrow component corresponds to static ordered domains. We interpret the speckles in the broad component as due to a very slow dynamical process, corresponding to the well-known central peak seen in inelastic neutron scattering. PACS numbers: 61.10.-i,68.35.Rh;77.84.Dy
Buried moiré supercells through SrTiO3 nanolayer relaxation
Physical Review Research
We identified a highly ordered moiré lattice at the buried SrTiO 3 (STO)-(La,Sr)(Al,Ta)-oxide (LSAT) interface by high-resolution x-ray diffraction reciprocal space mapping. We found long-ranged ordered supercells of 106/107 unit cells of unstrained STO-LSAT caused by complete lattice relaxation through high-temperature annealing. Transmission electron microscopy images show that this periodicity is based on line dislocations at the interface region. The presence of such ordered superstructures in such widely used complex oxides sets the ideal conditions for moiré-tuned interfacial electronic modifications and ferroelectric supercrystallinity, opening the possibility for interface functionalities and impacting findings on vortex structured multilayers systems.
Atomic-scale structural analyses of epitaxial Co∕Re superlattices
Applied Physics Letters, 2004
High-resolution transmission electron microscopy and scanning transmission electron microscopy (STEM) have been used to investigate atomic-scale structural properties of Co/ Re trilayers and superlattices grown via magnetron sputtering. The sample growth was epitaxial with the ͑1010͒ plane of Co and Re parallel to the ͑1120͒ plane of Al 2 O 3 , and the [001] direction of Re and Co coinciding with that of the Al 2 O 3. Both low-angle and high-angle Z-contrast STEM images show a very uniform layer thickness. However, the interface roughness between the Re and Co layers monotonically increases with interface distance from the substrate. These results strongly imply that, in the epitaxial Re/ Co superlattice system, interface roughness plays a more important role in the giant magnetoresistance effect than thickness fluctuations of the spacer layer. Previous anisotropic magnetoresistance measurements can be explained in terms of the observed atomic-scale structure.
Probing the Origin of Interfacial Carriers in SrTiO3–LaCrO3 Superlattices
Chemistry of Materials, 2017
Emergent phenomena at complex oxide interfaces could provide the basis for a wide variety of nextgeneration devices, including photovoltaics and spintronics. To date, detailed characterization and computational modeling of interfacial defects, cation intermixing, and film stoichiometry have helped to explain many of the novel behaviors observed at a single heterojunction. Unfortunately, many of the techniques employed to characterize a single heterojunction are less effective for a superlattice made up of a repeating series of interfaces that induce collective interfacial phenomena throughout a film. These repeating interfaces present an untapped opportunity to introduce an additional degree of complexity, such as confined electric fields, that cannot be realized in a single heterojunction. In this work, we explore the properties of SrTiO 3 −LaCrO 3 superlattices to understand the role of defects, including variations in cation stoichiometry of individual layers of the superlattice, intermixing across interfaces, and interfacial oxygen vacancies. Using X-ray photoelectron spectroscopy (XPS) and scanning transmission electron microscopy electron energy-loss spectroscopy (STEM-EELS), we quantify the stoichiometry of individual layers of the superlattice and determine the degree of intermixing in these materials. By comparing these results to both density functional theory (DFT) models and STEM-EELS measurements of the Ti and Cr valence in each layer of the superlattice, we correlate different types of defects with the associated materials properties of the superlattice. We show that a combination of ab initio modeling and complementary structural characterization methods can offer unique insight into structure−property relationships in many oxide superlattice systems.