Abstract
In electron cryomicroscopy (cryo-EM), molecular images of vitrified biological samples are obtained by conventional transmission microscopy (CTEM) using large underfocuses and subsequently ...computationally combined into a high-resolution three-dimensional structure. Here, we apply scanning transmission electron microscopy (STEM) using the integrated differential phase contrast mode also known as iDPC–STEM to two cryo-EM test specimens, keyhole limpet hemocyanin (KLH) and tobacco mosaic virus (TMV). The micrographs show complete contrast transfer to high resolution and enable the cryo-EM structure determination for KLH at 6.5 Å resolution, as well as for TMV at 3.5 Å resolution using single-particle reconstruction methods, which share identical features with maps obtained by CTEM of a previously acquired same-sized TMV data set. These data show that STEM imaging in general, and in particular the iDPC–STEM approach, can be applied to vitrified single-particle specimens to determine near-atomic resolution cryo-EM structures of biological macromolecules.
Ferroelectric domain formation is an essential feature in ferroelectric thin films. These domains and domain walls can be manipulated depending on the growth conditions. In rhombohedral BiFeO3 thin ...films, the ordering of the domains and the presence of specific types of domain walls play a crucial role in attaining unique ferroelectric and magnetic properties. In this study, controlled ordering of domains in BiFeO3 film is presented, as well as a controlled selectivity between two types of domain walls is presented, i.e., 71° and 109°, by modifying the substrate termination. The experiments on two different substrates, namely SrTiO3 and TbScO3, strongly indicate that the domain selectivity is determined by the growth kinetics of the initial BiFeO3 layers.
Growth of the BiFeO3 thin films is shown to depend on the atomic termination of the SrTiO3 and TbScO3 substrates. Interface engineering with a single SrO layer on substrate surfaces enables the control of domain ordering and selectivity between 71° and 109° domain walls. Underlying mechanism is claimed to be growth dynamic during the initial phase of growth.
Phase transitions that occur in materials, driven, for instance, by changes in temperature or pressure, can dramatically change the materials' properties. Discovering new types of transitions and ...understanding their mechanisms is important not only from a fundamental perspective, but also for practical applications. Here we investigate a recently discovered Fe4O5 that adopts an orthorhombic CaFe3O5-type crystal structure that features linear chains of Fe ions. On cooling below ∼150 K, Fe4O5 undergoes an unusual charge-ordering transition that involves competing dimeric and trimeric ordering within the chains of Fe ions. This transition is concurrent with a significant increase in electrical resistivity. Magnetic-susceptibility measurements and neutron diffraction establish the formation of a collinear antiferromagnetic order above room temperature and a spin canting at 85 K that gives rise to spontaneous magnetization. We discuss possible mechanisms of this transition and compare it with the trimeronic charge ordering observed in magnetite below the Verwey transition temperature.
Perovskite-like Mn2O3: A Path to New Manganites Ovsyannikov, Sergey V.; Abakumov, Artem M.; Tsirlin, Alexander A. ...
Angewandte Chemie (International ed.),
January 28, 2013, Letnik:
52, Številka:
5
Journal Article
Recenzirano
Phases of the Mn2O3: Two new phases of Mn2O3—corundum‐type ε‐Mn2O3 and perovskite‐type ζ‐Mn2O3—were obtained by high‐pressure high‐temperature synthesis. Manganese atoms were found to completely ...occupy the A‐ and B‐positions of perovskite simultaneously. The perovskite‐type ζ‐Mn2O3 has an A‐site‐ordered perovskite structure (see picture) containing Mn in three different oxidation states (+II, +III, and +IV).
Summary
The chemical composition, nanostructure and electronic structure of nanosized oxide scales naturally formed on the surface of AISI 316L stainless steel microfibres used for strengthening of ...composite materials have been characterised using a combination of scanning and transmission electron microscopy with energy‐dispersive X‐ray, electron energy loss and Auger spectroscopy. The analysis reveals the presence of three sublayers within the total surface oxide scale of 5.0–6.7 nm thick: an outer oxide layer rich in a mixture of FeO.Fe2O3, an intermediate layer rich in Cr2O3 with a mixture of FeO.Fe2O3 and an inner oxide layer rich in nickel.
•The Low-Mag Off-axis STEM-EELS set-up is used to determine the onset of the optical, direct bandgap of high refractive index GaAs-based materials.•This set-up gives the bandgap by simple regression ...analyses of the background subtracted EEL spectra.•The very low semi-convergence and –collection angles (µrad range) combined with off-axis/dark field EELS conditions made it possible to avoid Cerenkov losses, surface and interface plasmons and guided light modes in the EEL spectra.•The presented methodology can be applied over the entire acceleration voltage range of modern TEMs and for a wide range of specimen thicknesses.•Results from the various STEM EELS set-ups of bandgap measurements of GaAs-based materials were compared.
In the present work Cs aberration corrected and monochromated scanning transmission electron microscopy electron energy loss spectroscopy (STEM-EELS) has been used to explore experimental set-ups that allow bandgaps of high refractive index materials to be determined. Semi-convergence and –collection angles in the µrad range were combined with off-axis or dark field EELS to avoid relativistic losses and guided light modes in the low loss range to contribute to the acquired EEL spectra. Off-axis EELS further supressed the zero loss peak and the tail of the zero loss peak. The bandgap of several GaAs-based materials were successfully determined by simple regression analyses of the background subtracted EEL spectra. The presented set-up does not require that the acceleration voltage is set to below the Čerenkov limit and can be applied over the entire acceleration voltage range of modern TEMs and for a wide range of specimen thicknesses.
Ferroelectric domain formation is an essential feature in ferroelectric thin films. These domains and domain walls can be manipulated depending on the growth conditions. In rhombohedral BiFeO
3
thin ...films, the ordering of the domains and the presence of specific types of domain walls play a crucial role in attaining unique ferroelectric and magnetic properties. In this study, controlled ordering of domains in BiFeO
3
film is presented, as well as a controlled selectivity between two types of domain walls is presented, i.e., 71° and 109°, by modifying the substrate termination. The experiments on two different substrates, namely SrTiO
3
and TbScO
3
, strongly indicate that the domain selectivity is determined by the growth kinetics of the initial BiFeO
3
layers.
Ferroelectric domain formation is an essential feature in ferroelectric thin films. These domains and domain walls can be manipulated depending on the growth conditions. In rhombohedral BiFeO sub(3) ...thin films, the ordering of the domains and the presence of specific types of domain walls play a crucial role in attaining unique ferroelectric and magnetic properties. In this study, controlled ordering of domains in BiFeO sub(3) film is presented, as well as a controlled selectivity between two types of domain walls is presented, i.e., 71 degree and 109 degree , by modifying the substrate termination. The experiments on two different substrates, namely SrTiO sub(3) and TbScO sub(3), strongly indicate that the domain selectivity is determined by the growth kinetics of the initial BiFeO sub(3) layers. Growth of the BiFeO sub(3) thin films is shown to depend on the atomic termination of the SrTiO sub(3) and TbScO sub(3) substrates. Interface engineering with a single SrO layer on substrate surfaces enables the control of domain ordering and selectivity between 71 degree and 109 degree domain walls. Underlying mechanism is claimed to be growth dynamic during the initial phase of growth.
Co-rich ZnCoO nanoparticles embedded in wurtzite Zn0.7Co0.3O thin films are grown by pulsed laser deposition on a Si substrate. Local superconductivity with an onset Tc at 5.9 K is demonstrated in ...the hybrid system. The unexpected superconductivity probably results from Co3+ in the Co-rich ZnCoO nanoparticles or from the interface between the Co-rich nanoparticles and the Zn0.7Co0.3O matrix.
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