EELS elemental mapping with unconventional methods II. Applications to biological specimens

EELS elemental mapping with unconventional methods I. Theoretical basis: Image analysis with multivariate statistics and entropy concepts

The effect of a 10 nm Ce coating layer on long term oxidation behaviour (up to 3000 hours) of a Fe–22%Cr ferritic stainless steel for solid oxide fuel cell (SOFC) interconnect application is investigated. Scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS) analysis showed segregation of Ce to the grain boundaries of Cr,Mn spinel layer adjacent to the scale-gas interface. The findings in this study are in line with the grain boundary blocking model for the Ce effect mechanism. However, segregation of Ce was observed at the grain boundaries of the (Cr,Mn) spinel in the vicinity of the scale-gas interface. No evidence of Ce segregation was found in the grain boundaries of the chromia layer, neither any Ce rich particle was observed in the chromia layer after longer exposure times.

Towards atomically resolved EELS elemental and fine structure mapping via multi-frame and energy-offset correction spectroscopy

Among the instruments for solid state characterization working with a free electron probe, the Transmission Electron Microscope (TEM) has the best lateral resolution. The application is restricted, however, by the demand that the samples need to be suitably thinned. TEMs operating in the scanning mode yield several advantages. Equipped additionally with spectrometers, the TEM becomes an Analytical TEM. Energy Dispersive X-ray Spectroscopy (EDXS) and Electron Energy Loss Spectroscopy (EELS) allow the chemical analysis of the observed details of structure; the EELS permits additionally investigations on the electron configuration and on binding relations. Technical developments have increased considerably the information possibilities, such as lateral resolution or detection sensitivity. Recently two new types of instruments are in development, the dedicated Scanning-TEM with a field emission gun, supplying scanning images and analyses up to the nanometer range, and the energy filtering (stationary beam-) microscope which yields images and diffraction diagrams with a sharpness in contrast not previously reached. In the future the construction of an “aberration-free” objective lens promises a further advance into the atomic dimension.

This paper briefly reviews the potential applicability of analytical transmission electron microscopy (TEM) to elucidate both structural and chemical peculiarities of materials at high lateral resolution. Examples of analytical TEM investigations performed by energy-dispersive X-ray spectroscopy (EDXS), electron energy loss spectroscopy (EELS), and energy-filtered TEM (EFTEM) are presented for different materials systems including metals, ceramics, and compound semiconductors. In particular, results are given of imaging the element distribution in the interface region between gamma matrix and gamma' precipitate in the nickel-based superalloy SC16 by energy-filtered TEM. For core-shell structured BaTiO(3) particles the chemical composition and even the chemical bonding were revealed by EELS at a resolution of about 1 nm. A sub-nanometer resolution is demonstrated by energy-selective images of the Ga distribution in the surrounding of (In,Ga)As quantum dots. Moreover, the element distribution in (Al,Ga)As/AlAs multilayers with linear concentration gradients in a range of about 10 nm was investigated by EDXS line-profile analyses and EFTEM.

A survey is presented on the present state of the art in analytical transmission electron microscopy (ATEM). An essential advantage of this method is the simultaneous use of imaging, analytical and microdiffraction techniques with a lateral resolution in the 1.5 nm range. Two different analytical techniques are frequently used as ATEM attachments, energy dispersive X-ray spectrometry (EDXS) and electron energy loss spectrometry (EELS). Microscopic images with nanometer resolution may be also produced by energy selected imaging (ESI) with characteristic energy loss electrons. Advantages and limitations of all these methods will be discussed using actual material problems in the field of thin film research.

The mechanism of electrochromism for an amorphous WO3 film has been studied. The film was prepared by using vacuum evaporation. X-ray phototelectron spectroscopy analysis has revealed that a state appears below the Fermi level after coloration in a LiClO4-propylene carbonate electrolyte and that the Fermi level increases in proportion to the amount of injected lithium. In addition, a decrease in the density of state of the conduction band has been observed in a colored film by using electron energy loss spectroscopy analysis in transmission electron microscopy. It has been concluded that the electrons injected occupy the conduction band after coloration and that electrochromism of amorphous WO3 film is due to an intraband transition between an electron injected in the conduction band and an empty state.

Analytical TEM for the investigation of thin functional layers

Recently, Image processing (IP) and Machine learning (ML) algorithms have been successfully used in a wide variety of industry sectors. In this paper, we first provide mining engineers with the state of the art about IP and ML applications in the mining industry. furthermore, we propose a real time application for froth image analysis in the context of mineral processing. Finally, we propose some future directions, including suggestions on mining data collection and development of an exploration tool based on IP and ML algorithms by taking advantage of cloud computing technology to analyze geoscience data in order identify target areas with high prospectively potential.

Abstractauthoren Transmission electron microscopy (TEM) analysis, including energy dispersive X-ray (EDX) (elemental mapping, line, and point measurements) and energy filtered TEM (EFTEM) methods, is applied to investigate the high temperature reliability, especially material diffusion, of two types of diffusion barriers: titanium–tungsten-based (TiW-based) and tantalum-based (Ta-based), with nickel (Ni) layer on top. Both barriers were deposited as a form of stacked layers on sili-con (Si) wafers using the physical vapor deposition (PVD) technique. TEM analysis is performed on both barriers before and after annealing (at 600C for 24 h inside a vacuum chamber). No diffusion of material into the Si substrate as observed. Additionally, only diffusion between the Ni and adjoining TiW layers, and between Ni and adjoining Ta layers in the TiW-based and Ta-based barriers, respectively, are observed due to annealing.

In this article, an analysis of a failure in the embedded SRAM in a CMOS Image Sensor is investigated. The failure was due to unformed CoSi2. Because unformed CoSi2 causes a varying degree of response, a nano-prober was used to find the abnormally operating transistors among a 1-bit SRAM cell consisting of six transistors(6T). After measuring and analyzing the current-voltage relationships between each transistor, the current magnitude of one pull-down transistor was found to be less than the expected range and particularly lower than that of a connected access transistor. To visualize the failure phenomenon and find the root cause of this, TEM analysis was conducted. Using the EELS (Electron Energy Loss Spectroscopy) elemental mapping, unformed CoSi2 was detected between the contact and substrate, where the contact corresponds to the VSS of the pull-down transistor. This caused an increase in the contact resistance, thus lowering the current magnitude of the abnormal transistor to a greater degree than expected.

Mathematical morphology is a theory with applications in image processing and analysis. In a supervised approach to mathematical morphology, pixel values are ranked according to sets of foreground and background elements specified a priori by the user. In this paper, we introduce a supervised fuzzy color-based approach to color mathematical morphology that provides an elegant alternative to the support vector machine-based approach developed by Velasco-Forero and Angulo. Briefly, color elements are ranked according to the degree of truth of the proposition “the considered color is a foreground color but it is not a background color” in the new supervised color morphological approach. Furthermore, the vagueness and uncertainty inherent to the description of colors by humans can be naturally incorporated in the new approach using the concept of fuzzy colors.

Transmission electron microscopy (TEM) and analytic TEM were used to study the microstructure of amorphous carbon (a-C) films of thickness in the range of 5–100 nm deposited on Si(100) by radio-frequency (rf) sputtering. High-resolution cross-section TEM revealed a two-layer structure consisting of the a-C film and an ultrathin interface layer, in agreement with electron energy loss spectroscopy results. The presence of a 35-Å-thick interface layer (regardless of the deposition conditions) indicates that nucleation and initial growth of the a-C films were mainly controlled by the substrate surface condition. Mass-thickness contrast in bright-field TEM images showed an interface layer denser than the a-C film. This layer, believed to consist of Si, a-C, and SiC, enhances the adhesion of the film to the silicon substrate and accommodates the residual stress in the film. High-resolution cross-section TEM images revealed the presence of platelike nanocrystallites (∼35 Å in size) randomly distributed in the a-C film and oriented parallel to the surface. The possible mechanisms leading to the formation of these nanocrystalline structures are discussed in terms of sputtering phenomena occurring during film deposition.

Single-crystalline MnOOH and Mn3O4 nanowires have been prepared by hydrothermal treatment of commercial bulky manganese oxide particles. β-MnO2 and α-Mn2O3 nanowires were prepared by calcination of MnOOH nanowires. Transmission electron microscopy analysis demonstrates that MnOOH nanowires grow directly from MnO2 raw particles. The diameter of the nanowires is 20–70 nm, while the length can reach several micrometers. MnOOH nanowires grow preferentially along the [010] direction and Mn3O4 nanowires prefer to grow along the [001] direction; the long dimension of both β-MnO2 and α-Mn2O3 nanowires is along [001]. Electron energy-loss spectroscopy analysis shows that the position of the prepeak of the oxygen K edge shifts to higher energy and the energy separation between the two main peaks of the oxygen K edge decreases with decreasing manganese oxidation state. The manganese-white-line ratios (L3∕L2) were calculated.

A thriving field in nanotechnology is to develop synergetic functions of nanomaterials by taking full advantages of unique properties of each component. In this context, combining TiO2 nanocrystals and carbon nanotubes (CNTs) offers enhanced photosensitivity and improved photocatalytic efficiency, which is key to achieving sustainable energy and preventing environmental pollution. Hence, it has aroused a tremendous research interest. This report surveys recent research on the topic of synthesis and characterization of the CNT–TiO2 interface. In particular, atomic layer deposition (ALD) offers a good control of the size, crystallinity and morphology of TiO2 on CNTs. Analytical transmission electron microscopy (TEM) techniques such as electron energy loss spectroscopy (EELS) in scanning transmission mode provides structural, chemical and electronic information with an unprecedented spatial resolution and increasingly superior energy resolution, and hence is a necessary tool to characterize the CNT–TiO2 interface, as well as other technologically relevant CNT–metal/metal oxide material systems.