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Electric field reconstruction at interfaces plays a crucial role in device performances controlling, for example, Schottky potential barrier and interfacial Rashba effect. Here, scanning transmission electron microscopy (STEM) and ab‐initio calculation are used to estimate the atomic‐scale and large‐scale potential reconstruction at the interface between a metallic oxide SrRuO3 (SRO) thin film and an insulating DyScO3 (DSO) substrate. The intensity and the symmetry of the large‐scale electrostatic reconstruction at the interface is probed by 4D‐STEM discussing the center‐of‐mass shift for different angular ranges detection. Numerical simulations indicate that thermal diffuse scattered (TDS) electrons can be sensitive to large‐scale electric field and experiments based on these diffused electrons near the interface confirm that the electric field extends more in the insulating DyScO3 (DSO) side. The magnitude of the electrostatic drop at the interface estimated by the 4D‐STEM experiment is in accordance with the ab‐initio values for a p‐type reconstruction of the interface plane. Furthermore, an atomically resolved TDS potential asymmetry is observed in real‐space at the SRO/DSO interface by 4D‐STEM. This asymmetry is associated with the formation of a local ferroelectric type dipole at the interfacial unit‐cell revealing unambiguously the balance evolution between antiferrodistortive and ferroelectric instabilities at the interface between a metallic SRO and an insulating DSO. Scanning transmission electron microscopy (STEM) and ab‐initio calculations estimate the atomic‐scale and large‐scale potential reconstruction at the interface between a metallic oxide SrRuO3 (SRO) thin film and an insulating DyScO3 (DSO) substrate. The 4D‐STEM experiments and calculations take into account the thermal diffuse scattered electrons in order to estimate the large‐scale electrostatic potential discontinuity at the SRO/DSO interface.

Atomic-scale defects in graphene layers alter the physical and chemical properties of carbon nanostructures 1 , 2 . Theoretical predictions have recently shown that energetic particles such as electrons and ions can induce polymorphic atomic defects in graphene layers as a result of knock-on atom displacements 3 , 4 . However, the number of experimental reports on these defects is limited 5 , 6 . The graphite network in single-walled carbon nanotubes has been visualized by transmission electron microscopy (TEM) and their chiral indices have been determined 7 , 8 . But the methods used require a long image acquisition time and intensive numerical treatments after observations to find an ‘average’ image, which prevents the accurate detection and investigation of defect structures. Here we report observations in situ of defect formation in single graphene layers by high-resolution TEM. The observed structures are expected to be of use when engineering the properties of carbon nanostructures for specific device applications.

Perovskite rare‐earth titanates RTiO3 display a rich array of magnetic and electronic properties, with a Mott‐insulating ground state and ferro‐ or antiferromagnetic spin orders depending on the rare‐earth R. The nominal Ti valence is 3+ with a corresponding 3d1 configuration. Yet, at the surface of both bulk and thin films of RTiO3, the Ti valence has been found to strongly deviate towards the more stable 4+ state, adversely affecting magnetic properties. While this finding is rather ubiquitous, its exact origin is still poorly understood, which hampers the integration of RTiO3 into complex heterostructures harnessing their rich physics. Here, scanning transmission electron microscope and electron energy loss spectroscopy experiments are used to analyze the top part of an epitaxial DyTiO3 thin film displaying a well‐developed Ti4+‐rich layer over several nanometres. It shows that this valence evolution is related to a combination of short‐range ordered interstitial oxygen planes and Ti‐Dy cationic imbalance. Both defects synergistically contribute to enough hole doping for a complete transition toward Ti4+ over a few unit‐cells from the surface while a structure primarily of the perovskite‐type is maintained. DyTiO3 perovskite titanates exhibit ferri‐magnetic ordering. Despite a nominal Ti valence of 3+, surface deviations to a more stable 4+ state disrupt this magnetic behavior for thin films. This valence evolution arises from short‐range ordered interstitial oxygen planes and Ti‐Dy cationic imbalance, inducing sufficient hole doping for a complete Ti4+ transition over a few unit‐cells near the surface, while maintaining a perovskite structure.

The nature of lead zirconate, the historical antiferroelectric material, has recently been challenged. In PbZrO 3 epitaxial films, thickness reduction engenders competition among antiferroelectric, ferrielectric and ferroelectric phases. All studies so far on PbZrO 3 films have utilized commercially-available oxide single crystals with large compressive lattice mismatch, causing the films to undergo strain relaxation. First-principles calculations have predicted that tensile strain can stabilize antiferroelectricity down to the nanometre scale. Here we use tensile strain imposed by artificial substrates of LaLuO 3 to stabilize a pure antiferroelectric phase in PbZrO 3 . Sharp double hysteresis loops of polarization vs electric field show zero remanent polarization, and polar displacement maps reveal the characteristic up-up-down-down antipolar pattern down to 9 nanometre film thicknesses. Moreover, the electron beam can move this antipolar pattern through the nucleation and annihilation of translational boundaries. These results highlight the critical role of coherent epitaxial strain in the phase stability of PbZrO 3 . Here the authors use tensile strain imposed by artificial substrates of LaLuO3 to stabilize a pure antiferroelectric phase in epitaxial thin films of PbZrO3.

Strain accommodation in upper crustal rocks is often accompanied by fluid-mediated crystallization of phyllosilicates, which influence rock strength and shear zone formation. The composition of these phyllosilicates is frequently used for pressure–temperature–time constraints of deformation events, although it is often highly heterogeneous, even in mylonites. This study investigates the reactions producing a phyllosilicate, chlorite, in and below greenschist-facies conditions and the variations in chlorite composition along a strain gradient in the Variscan Bielsa granitoid (axial zone, Pyrenees). Compositional maps of chlorite including iron speciation are compared to nanostructures observed by transmission electron microscopy in increasingly-strained samples and related to mechanisms of fluid percolation. In the Bielsa granitoid, altered at the late-Variscan, Alpine-age shear zones are found with high strain gradients. The undeformed granitoid exhibits local equilibria, pseudomorphic replacement, and high compositional heterogeneities in chlorite. This is attributed to variable reaction mechanisms at nanoscale and element supply, little interconnected intra- and inter-grain nanoporosity, and isolation of fluid evolving in local reservoirs. In samples with discrete and mm-sized fractures, channelized fluid triggered the precipitation of homogeneous Alpine chlorite in fractures, preserving late-Variscan chlorite within the matrix. In low-grade mylonites, where brittle–ductile deformation is observed, micro- and nanocracks and defects allow the fluid percolating into the matrix at the scale of hundreds of µm. This results in a more pervasive but incomplete replacement of late-Variscan chlorite by Alpine chlorite, despite the high strain. In studied granitoids deformed under greenschist-facies conditions, local equilibria and high compositional heterogeneities in phyllosilicates as chlorite are therefore preserved according to reaction mechanisms and element mobility controlled by (1) matrix-fracture porosity contrasts at nanoscale and (2) the location and interconnection of nanoporosity between crystallites of phyllosilicates. This preservation influences our ability to reconstruct the pre- and syn-kinematic metamorphic history of granitic rocks in low-grade units of orogens.

The global geochemical carbon cycle involves exchanges between the Earth's interior and the surface. Carbon is recycled into the mantle via subduction mainly as carbonates and is released to the atmosphere via volcanism mostly as CO₂. The stability of carbonates versus decarbonation and melting is therefore of great interest for understanding the global carbon cycle. For all these reasons, the thermodynamic properties and phase diagrams of these minerals are needed up to core mantle boundary conditions. However, the nature of C-bearing minerals at these conditions remains unclear. Here we show the existence of a new Mg-Fe carbon-bearing compound at depths greater than 1,800 km. Its structure, based on three-membered rings of corner-sharing (CO₄)⁴⁻ tetrahedra, is in close agreement with predictions by first principles quantum calculations [Oganov AR, et al. (2008) Novel high-pressure structures of MgCO₃, CaCO₃ and CO₂ and their role in Earth's lower mantle. Earth Planet Sci Lett 273:38-47]. This high-pressure polymorph of carbonates concentrates a large amount of Fe⁽III⁾ as a result of intracrystalline reaction between Fe⁽II⁾ and (CO₃)²⁻ groups schematically written as 4FeO + CO₂ [rightward arrow] 2Fe₂O₃ + C. This results in an assemblage of the new high-pressure phase, magnetite and nanodiamonds.

TiO2 nanoparticles have generally low toxicity in the in vitro systems although some toxicity is expected to originate in the TiO2-associated photo-generated radical production, which can however be modulated by the radical trapping ability of the serum proteins. To explore the role of serum proteins in the phototoxicity of the TiO2 nanoparticles we measure viability of the exposed cells depending on the nanoparticle and serum protein concentrations. Fluorescence and spin trapping EPR spectroscopy reveal that the ratio between the nanoparticle and protein concentrations determines the amount of the nanoparticles' surface which is not covered by the serum proteins and is proportional to the amount of photo-induced radicals. Phototoxicity thus becomes substantial only at the protein concentration being too low to completely coat the nanotubes' surface. These results imply that TiO2 nanoparticles should be applied with ligands such as proteins when phototoxic effects are not desired - for example in cosmetics industry. On the other hand, the nanoparticles should be used in serum free medium or any other ligand free medium, when phototoxic effects are desired - as for efficient photodynamic cancer therapy.

La 0.7 Sr 0.3 MnO 3 , a half-metallic ferromagnet with full spin polarization, is generally used as a standard spin injector in heterostructures. However, the magnetism of La 0.7 Sr 0.3 MnO 3 is strongly modified near interfaces, which was addressed as “dead-layer” phenomenon whose origin is still controversial. Here, both magnetic and structural properties of La 0.7 Sr 0.3 MnO 3 /SrTiO 3 heterostructures were investigated, with emphasis on the quantitative analysis of oxygen octahedral rotation (OOR) across interfaces using annular-bright-field imaging. OOR was found to be significantly altered near interface for both La 0.7 Sr 0.3 MnO 3 and SrTiO 3 , as linked to the magnetism deterioration. Especially in La 0.7 Sr 0.3 MnO 3 /SrTiO 3 superlattices, the almost complete suppression of OOR in 4 unit-cell-thick La 0.7 Sr 0.3 MnO 3 results in a canted ferromagnetism. Detailed comparisons between strain and OOR relaxation and especially the observation of an unexpected La 0.7 Sr 0.3 MnO 3 lattice c expansion near interfaces, prove the relevance of OOR for the magnetic properties. These results indicate the capability of tuning the magnetism by engineering OOR at the atomic scale.

Infinite layer (IL) nickelates provide a new route beyond copper oxides to address outstanding questions in the field of unconventional superconductivity. However, their synthesis poses considerable challenges, largely hindering experimental research on this new class of oxide superconductors. That synthesis is achieved in a two‐step process that yields the most thermodynamically stable perovskite phase first, then the IL phase by topotactic reduction, the quality of the starting phase playing a crucial role. Here, a reliable synthesis of superconducting IL  nickelate films is reported after successive topochemical reductions of a parent perovskite phase with nearly optimal stoichiometry. Careful analysis of the transport properties of the incompletely reduced films reveals an improvement in the strange metal behavior of their normal state resistivity over subsequent topochemical reductions, offering insight into the reduction process. Infinitelayer (IL) nickelate superconductors are synthesized by successive topochemical reductions of the perovskite phase. Careful analysis of the transport properties of the incompletely reduced films reveals an improvement in the strange metal behavior of their normal state resistivity over subsequent reductions. Removal of the apical oxygen anions from the perovskite phase is confirmed through the structural analysis of the IL phase.

The mixing state of aerosols collected at M'Bour, Senegal, during the Special Observing Period conducted in January–February 2006 (SOP‐0) of the African Monsoon Multidisciplinary Analysis project (AMMA), was studied by individual particle analysis. The sampling location on the Atlantic coast is particularly adapted for studying the mixing state of tropospheric aerosols since it is (1) located on the path of Saharan dust plumes transported westward over the northern tropical Atlantic, (2) influenced by biomass burning events particularly frequent from December to March, and (3) strongly influenced by anthropogenic emissions from polluted African cities. Particle size, morphology, and chemical composition were determined for 12,672 particles using scanning electron microscopy (automated SEM‐EDX). Complementary analyses were performed using transmission electron microscopy combined with electron energy loss spectrometry (TEM‐EELS) and Raman microspectrometry. Mineral dust and carbonaceous and marine compounds were predominantly found externally mixed, i.e., not present together in the same particles. Binary internally mixed particles, i.e., dust/carbonaceous, carbonaceous/marine, and dust/marine mixtures, accounted for a significant fraction of analyzed particles (from 10.5% to 46.5%). Western Sahara was identified as the main source of mineral dust. Two major types of carbonaceous particles were identified: “tar balls” probably coming from biomass burning emissions and soot from anthropogenic emissions. Regarding binary internally mixed particles, marine and carbonaceous compounds generally formed a coating on mineral dust particles. The carbonaceous coating observed at the particle scale on African dust was evidenced by the combined use of elemental and molecular microanalysis techniques, with the identification of an amorphous rather than crystallized carbon structure.