In-situ isotopic analysis at nanoscale using parallel ion electron spectrometry: a powerful new paradigm for correlative microscopy

Isotopic analysis is of paramount importance across the entire gamut of scientific research. To advance the frontiers of knowledge, a technique for nanoscale isotopic analysis is indispensable. Secondary Ion Mass Spectrometry (SIMS) is a well-established technique for analyzing isotopes, but its spatial-resolution is fundamentally limited. Transmission Electron Microscopy (TEM) is a well-known method for high-resolution imaging down to the atomic scale. However, isotopic analysis in TEM is not possible. Here, we introduce a powerful new paradigm for in-situ correlative microscopy called the Parallel Ion Electron Spectrometry by synergizing SIMS with TEM. We demonstrate this technique by distinguishing lithium carbonate nanoparticles according to the isotopic label of lithium, viz. 6Li and 7Li and imaging them at high-resolution by TEM, adding a new dimension to correlative microscopy

Electron energy-loss spectroscopic tomography of FexCo(3-x)O4 impregnated Co3O4 mesoporous particles: unraveling the chemical information in three dimensions

Electron energy-loss spectroscopy-spectrum image (EELS-SI) tomography is a powerful tool to investigate the three dimensional chemical configuration in nanostructures. Here, we demonstrate, for the first time, the possibility to characterize the spatial distribution of Fe and Co cations in a complex FexCo(3-x)O4/Co3O4 ordered mesoporous system. This hybrid material is relevant because of the ferrimagnetic/antiferromagnetic coupling and high surface area. We unambiguously prove that the EELS-SI tomography shows a sufficiently high resolution to simultaneously unravel the pore structure and the chemical signal

Oxide wizard: an EELS application to characterize the white lines of transition metal edges

Physicochemical properties of transition metal oxides are directly determined by the oxidation state of the metallic cations. To address the increasing need to accurately evaluate the oxidation states of transition metal oxide systems at the nanoscale, here we present Oxide Wizard. This script for Digital Micrograph characterizes the energy-loss near-edge structure and the position of the transition metal edges in the electron energy-loss spectrum. These characteristics of the edges can be linked to the oxidation states of transition metals with high spatial resolution. The power of the script is demonstrated by mapping manganese oxidation states in Fe3O4/Mn3O4 core/shell nanoparticles with sub-nanometer resolution in real spac

EEL spectroscopic tomography: Towards a new dimension in nanomaterials analysis

Electron tomography is a widely spread technique for recovering the three dimensional (3D) shape of nanostructured materials. Using a spectroscopic signal to achieve a reconstruction adds a fourth chemical dimension to the 3D structure. Up to date, energy filtering of the images in the transmission electron microscope (EFTEM) is the usual spectroscopic method even if most of the information in the spectrum is lost. Unlike EFTEM tomography, the use of electron energy-loss spectroscopy (EELS) spectrum images (SI) for tomographic reconstruction retains all chemical information, and the possibilities of this new approach still remain to be fully exploited. In this article we prove the feasibility of EEL spectroscopic tomography at low voltages (80kV) and short acquisition times from data acquired using an aberration corrected instrument and data treatment by Multivariate Analysis (MVA), applied to FexCo(3-x)O4@Co3O4 mesoporous materials. This approach provides a new scope into materials; the recovery of full EELS signal in 3D

Patterning enhanced tetragonality in BiFeO3 thin films with effective negative pressure by helium implantation

Helium implantation in epitaxial thin films is a way to control the out-of-plane deformation independentlyfrom the in-plane strain controlled by epitaxy. In particular, implantation by means of a helium microscopeallows for local implantation and patterning down to the nanometer resolution, which is of interest for deviceapplications. We present here a study of bismuth ferrite (BiFeO3) films where strain was patterned locally byhelium implantation. Our combined Raman, x-ray diffraction, and transmission electron microscopy (TEM)study shows that the implantation causes an elongation of the BiFeO3unit cell and ultimately a transition towardsthe so-called supertetragonal polymorph via states with mixed phases. In addition, TEM reveals the onset ofamorphization at a threshold dose that does not seem to impede the overall increase in tetragonality. The phasetransition from the R-like to T-like BiFeO3appears as first-order in character, with regions of phase coexistenceand abrupt changes in lattice parameters

3D Visualization of the Iron Oxidation State in FeO/Fe3O4 Core-Shell Nanocubes from Electron Energy Loss Tomography.

Left panel shows the explained variance ratio of the principal component analysis (PCA) decomposition. The six first components, which are enough to explain the whole data set, are plotted in the right panel. Components 0, 3 and 5 show no remarkable features in the Fe L2,3 ionization energy and seem rather related to the background of the spectra due to their power-law behaviour, while component 1 is almost constant and therefore could be related to the dark noise in the detector

Controlled 3D-coating of the pores of highly ordered mesoporous antiferromagnetic Co3O4 replicas with ferrimagnetic FexCo3-xO4 nanolayers

The controlled filling of the pores of highly ordered mesoporous antiferromagnetic Co3O4 replicas with ferrimagnetic FexCo3-xO4 nanolayers is presented as a proof-of-concept toward the integration of nanosized units in highly ordered, heterostructured 3D architectures. Antiferromagnetic (AFM) Co3O 4 mesostructures are obtained as negative replicas of KIT-6 silica templates, which are subsequently coated with ferrimagnetic (FiM) Fe xCo3-xO4 nanolayers. The tuneable magnetic properties, with a large exchange bias and coercivity, arising from the FiM/AFM interface coupling, confirm the microstructure of this novel two-phase core-shell mesoporous material. The present work demonstrates that ordered functional mesoporous 3D-materials can be successfully infiltrated with other compounds exhibiting additional functionalities yielding highly tuneable, versatile, non-siliceous based nanocomposites

Towards a new dimension in analytical TEM: EELS, Tomography and the Spectrum Volume

[cat] En el microscopi electrònic de transmissió (TEM), es poden obtenir imatges d’una mostra des de diferents angles i posteriorment reconstruir aquestes imatges en tres dimensions (3D). Per altra banda, les interaccions dels electrons del feix amb els electrons de la mostra poden ser analitzades mitjançant l’espectroscòpia de pèrdues d’energia dels electrons (EELS), obtenint així informació química de la mostra. L’objectiu d’aquesta tesi és la combinació de l’espectroscòpia EELS amb la tomografia electrònica per obtenir informació química en 3 dimensions a la nanoescala. S’han explicat les bases de la tomografia electrònica i el procediment de la reconstrucció ha estat il•lustrat amb una mostra de nanocubs d’òxid de ferro. Posteriorment, s’ha aplicat a una sèrie de nanopartícules de Cu2O per tal de descriure’n la forma. També s’ha explicat la física en què es basa l’EELS, fent especial atenció als llindars d’altes pèrdues d’energia. A continuació, s’ha mostrat l’augment del senyal obtingut amb precessió electrònica al TEM quan la mostra es troba en condicions d’eix de zona. Seguint amb les aplicacions d’EELS, s’ha explotat la possibilitat de caracteritzar els estats d’oxidació dels metalls de transició mitjançant un programa propi, escrit per a Digital Micrograph i anomenat Oxide Wizard. Una vegada la tomografia electrònica i l’espectroscòpia de pèrdues d’energia dels electrons han estat explicades, s’ha procedit a reconstruir informació extreta d’EELS en 3D. S’han realitzat una sèrie d’experiments amb partícules mesoporoses que han demostrat la utilitat d’aplicar l’anàlisi multivariable per tal de reduir el soroll de les dades i extreure’n els components. Finalment, s’ha dissenyat un experiment en el qual ha estat possible recuperar l’espectre corresponent a cada unitat d’espai com la combinació d’espectres propis en una mostra preparada en forma de nanoagulla. Els espectres recuperats corresponen a la contribució de cada unitat de volum als espectres projectats. Aquest nou tipus de dades permet extreure espectres de l’interior d’una mostra. Finalment, doncs, s’ha pogut combinar amb èxit la tomografia electrònica i EELS per obtenir informació química en tres dimensions a la nanoescala.[eng] The main goal of this thesis is to combine electron tomography and electron energy loss spectroscopy (EELS) in the TEM, in order to obtain chemical and electronic information in 3D in the nanoscale. Tomography in the TEM has been discussed and the advantages and disadvantages of HAADF STEM tomography have been analyzed. - A Fe3O4 nanocube sample has been considered to illustrate the acquisition, alignment, tilt axis assessment, reconstruction and visualization processes. - HAADF STEM tomography has been used to reconstruct the shape of a series of Cu2O nanoparticles. For one of the samples, the facets of the Cu2O nanoparticles, octahedral in shape, have been found to correspond to {111} planes. The physics and the data analysis methods of core-loss EELS have been briefly summarized. Two relevant contributions have been made: - The effects of beam precession on EELS have been investigated. A signal enhancement due to electron beam precession in the TEM when in zone axis conditions has been discovered for the first time. - A homemade software, Oxide Wizard, for valence state determination of transition metals has been developed and applied to map the Mn oxidation state of a MnOx/FeOy nanoparticle. EELS spectrum imaging and electron tomography have been combined to recover chemical information in 3D for FexCo(3-x)O4@Co3O4 mesoporous nanoparticles. - The samples have been first characterized by HAADF STEM tomography and EELS. - EELS chemical information is, of course, limited to 2D maps, while only structural information is be recovered in 3D form HAADF tomography. . An EELS-SI tilt series has been acquired at 80 kV and low acquisition times, resulting in a very noisy dataset. - Principal component analysis (PCA) has been used to separate the noise from the signal. - Quantifications of the O, Fe and Co signals have been reconstructed, and the shape of the particle recovered. - From the noise clean dataset, components with physical meaning (iron oxide, cobalt oxide and thickness) have been extracted using independent component analysis (ICA), and reconstructed in 3D. - A new kind of signal with chemical and thickness information has been obtained by combining the thickness component with the quantification results. This signal is able to properly reconstruct the chemical structure of the sample in 3D, detecting a higher presence of iron in the surface, and an even distribution of Fe inside of the particle. . Another EELS-SI tilt series has been acquired at 80 kV and low acquisition times with enough spatial resolution to resolve the porous structure. - The noise has been reduced using PCA. - Four signals extracted from the spectrum have been reconstructed: the integrated edge intensities for oxygen, iron and cobalt, and the integrated background prior to the oxygen edge. EELS-SI tomography has been applied to reconstruct CoFe2O4 (CFO) nanocolumns embedded in a BiFeO3 (BFO) matrix grown on LaNiO3 buffered LaAlO3 substrate (BFO-CFO//LNO/LAO). - The nanocomposite sample has been prepared in a nanoneedle shape by means of focused ion beam (FIB). This preparation has the advantage of keeping the thickness of the sample constant throughout the tilting experiment. The nanoneedle contains an island of CFO in a matrix of BFO, as well as the LNO/LAO substrate. - The noise has been discarded using PCA. - The oxygen, iron and lanthanum edges intensities have been extracted and reconstructed. A new kind of data hypercube, the Spectrum Volume, has been proposed. Just as a Spectrum Image contains a spectrum per pixel, a Spectrum Volume is to contain a spectrum per voxel. EELS-SI tomography has been applied to successfully acquire a spectrum volume (SV) of the (BFO-CFO//LNO/LAO) system. - PCA has been used to discard the noise and Bayesian linear unmixing (BLU) has been used to extract independent components (eigenspectra). - Each eigenspectrum has a 2D weighting map for each tilt; weighting maps have been reconstructed into 3D weighting volumes. - Full single spectra for any point in the reconstructed space can now be recovered as a weighed sum of eigenspectra, using the 3D weighting distributions. This approach is used to extract single spectra, spectrum lines and spectrum images from the inside of the sample. In the context of this thesis, tomography and EELS-SI have been combined to successfully recover chemical information in 3D at the nanoscale, and a new kind of data hypercube, the Spectrum Volume, has been proposed and experimentally recovered

Arc erosion behaviour of platinum based and silver Lehrstuhl für Funktionswerkstoffe based composites

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Arc erosion behaviour of platinum based and silver Lehrstuhl für Funktionswerkstoffe based composites

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