Summary


The spatial resolution of electron diffraction within the scanning electron microscope (SEM) has progressed from channelling methods capable of measuring crystallographic characteristics from 10 μm regions to electron backscatter diffraction (EBSD) methods capable of measuring 120 nm particles Here, we report a new form of low-energy transmission Kikuchi diffraction, performed in the SEM Transmission-EBSD (t-EBSD) makes use of an EBSD detector and software to capture and analyse the angular intensity variation in large-angle forward scattering of electrons in transmission, without postspecimen coils We collected t-EBSD patterns from Fe–Co nanoparticles of diameter 10 nm and from 40 nm-thick Ni films with in-plane grain size 15 nm The patterns exhibited contrast similar to that seen in EBSD, but are formed in transmission Monte Carlo scattering simulations showed that in addition to the order of magnitude improvement in spatial resolution from isolated particles, the energy width of the scattered electrons in t-EBSD is nearly two orders of magnitude narrower than that of conventional EBSD This new low-energy transmission diffraction approach builds upon recent progress in achieving unprecedented levels of imaging resolution for materials characterization in the SEM by adding high-spatial-resolution analytical capabilities

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Transmission EBSD from 10 nm domains in a scanning electron microscope

Properties and Application of Geopolymers Vol. 841 (/MSF.841 /book) Development and Investigation of Materials Using Modern Techniques Vol. 840 (/MSF.840/book) Superplasticity in Advanced Materials ICSAM 2015 Vols. 838-839 (/MSF.838-839/book) 12th International Conference on High Speed Machining Vols. 836-837 (/MSF.836-837/book) Sintering Fundamentals II Vol. 835 (/MSF.835/book) Advanced Machining Technologies: Traditions and Innovations Vol. 834 (/MSF.834/book) Applied Materials and Technologies Vol. 833 (/MSF.833/book) Emerging Functional Materials: Book (/MSF.841/book) Papers (/MSF.841)

Materials Science Forum

Microstructure characterization has become indispensable to the study of complex materials, such as strongly correlated oxides, and can obtain useful information about the origin of their physical properties. Although atomically resolved measurements have long been possible, an important goal in microstructure characterization is to achieve element-selective imaging at atomic resolution. A combination of scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy (EELS) is a promising technique for atomic-column analysis. However, two-dimensional analysis has not yet been performed owing to several difficulties, such as delocalization in inelastic scattering or instrumentation instabilities. Here we demonstrate atomic-column imaging of a crystal specimen using localized inelastic scattering and a stabilized scanning transmission electron microscope. The atomic columns of La, Mn and O in the layered manganite La1.2Sr1.8Mn2O7 are visualized as two-dimensional images.

Element-selective imaging of atomic columns in a crystal using STEM and EELS

The ability to localize, identify, and measure the electronic environment of individual atoms will provide fundamental insights into many issues in materials science, physics, and nanotechnology. We demonstrate, using an aberration-corrected scanning transmission electron microscope, the spectroscopic imaging of single La atoms inside ${\mathrm{C}\mathrm{a}\mathrm{T}\mathrm{i}\mathrm{O}}_{3}$. Dynamical simulations confirm that the spectroscopic information is spatially confined around the scattering atom. Furthermore, we show how the depth of the atom within the crystal may be estimated.

Spectroscopic imaging of single atoms within a bulk solid.

Publisher Summary This chapter describes the way in which an annular dark-field (ADF) image is formed in a scanning transmission electron microscope (STEM). ADF imaging refers to the use of particular detector geometry in STEM. A geometrically large annular detector is placed in the optical far field beyond the specimen. The total intensity detected over the whole detector is recorded and displayed as a function of the position of the illuminating probe. Because the detector only receives a signal when the specimen is present, the vacuum appears dark, hence the name, and the heavier the atom, the higher the intensity of the scattering, which leads to atomic number (Z) contrast in the image. The most important feature of ADF imaging is that it can be described as being incoherent that has many advantages at atomic resolution. The chapter explains the way in which the image data may be used to provide atomic-resolution information about the specimen.

The principles and interpretation of annular dark-field Z-contrast imaging

A new type of scanning electron microscope with aberration correction allows a resolution of 0.1 nm. The instrument also allows for simultaneous imaging of atoms on the surface and in the bulk of a sample, which represents a real breakthrough in the field. Aberration correction has embarked on a new frontier in electron microscopy by overcoming the limitations of conventional round lenses, providing sub-angstrom-sized probes1,2,3,4,5,6,7,8. However, improvement of spatial resolution using aberration correction so far has been limited to the use of transmitted electrons both in scanning and stationary mode, with an improvement of 20–40% (refs 3–8). In contrast, advances in the spatial resolution of scanning electron microscopes (SEMs), which are by far the most widely used instrument for surface imaging at the micrometre–nanometre scale9, have been stagnant, despite several recent efforts10,11. Here, we report a new SEM, with aberration correction, able to image single atoms by detecting electrons emerging from its surface as a result of interaction with the small probe. The spatial resolution achieved represents a fourfold improvement over the best-reported resolution in any SEM (refs 10–12). Furthermore, we can simultaneously probe the sample through its entire thickness with transmitted electrons. This ability is significant because it permits the selective visualization of bulk atoms and surface ones, beyond a traditional two-dimensional projection in transmission electron microscopy. It has the potential to revolutionize the field of microscopy and imaging, thereby opening the door to a wide range of applications, especially when combined with simultaneous nanoprobe spectroscopy.

http://www.eecs.umich.edu/zhonglab/pub/nmat2532.pdf

Imaging single atoms using secondary electrons with an aberration-corrected electron microscope

A scanning transmission electron microscope (STEM) has an electron source for generating a primary electron beam and an electron illuminating lens system for converging the primary electron beam from the electron source onto a specimen for illumination. An electron deflecting system is provided for scanning the specimen with the primary electron beam. The STEM also has a scattered electron detector for detecting scattered electrons transmitted through the specimen. A projection lens system projects the scattered electrons onto a detection surface of the scattered electron detector. An image displaying device displays the scanning transmission electron microscope image of the specimen using a detection signal from the scattered electron detector. A detection angle changing device for establishes the range of the scattering angle of the scattered electrons detected by the scattered electron detector. This structure enhances the contrast of a desired portion of the specimen under observation for a scanning transmitted image by selective establishment of detection angle ranges for the scattered electron detector.

Method and apparatus for scanning transmission electron microscopy

Position dependence of the visibility of a single gold atom in silicon crystals in haadf-stem image simulation

Disclosed is an observation apparatus and method using an electron beam, capable of measuring information regarding a crystal structure in a specimen (such as information regarding stress and strain in the specimen) with high sensitivity and high resolution from an electron beam diffraction image obtained by irradiating the specimen with an electron beam. An observation method according to the invention includes: a step of mounting a specimen on a specimen stage; an enlarged image acquiring step of irradiating a predetermined area in the specimen with an electron beam while scanning the electron beam, and acquiring an enlarged image of a specimen internal structure in the predetermined area in the specimen by using the electron beam passed through the specimen; a diffraction image acquiring step of irradiating a specific portion included in the predetermined area in the specimen with the electron beam and acquiring a diffraction image including information of a crystal structure in the specimen in the specific portion in the specimen, formed by the electron beam diffracted in the specimen; a crystal structure information extracting step of extracting information of the crystal structure in the specimen from the diffracted image acquired in the diffraction image acquiring step; and a superimposing and displaying step of displaying the information of the crystal structure in the specimen extracted in the crystal structure information extracting step so as to be superimposed on the enlarged image acquired in the enlarged image acquiring step. The observation method according to the invention can obtain information of the crystal structure in a specimen with high sensitivity and high resolution.

Observation apparatus and observation method using an electron beam

A bio electron microscope and an observation method which can observe a bio specimen by low damage and high contrast to perform high-accuracy image analysis, and conduct high-throughput specimen preparation. 1) A specimen is observed at an accelerating voltage 1.2 to 4.2 times a critical electron accelerating voltage possible to transmit a specimen obtained under predetermined conditions. 2) An electron energy filter of small and simplified construction is provided between the specimen and an electron detector for imaging by the electron beam in a specified energy region of the electron beams transmitting the specimen. 3) Similarity between an observed image such as virus or protein in the specimen and a reference image such as known virus or protein is subjected to quantitative analysis by image processing. 4) A preparation protocol of the bio specimen is made into a chip using an MEMS technique, which is then mounted on a specimen stage part of an electron microscope to conduct specimen introduction, preparation and transfer onto a specimen holder.

Kuniyasu Nakamura

Papers

Imaging single atoms using secondary electrons with an aberration-corrected electron microscope

Method and apparatus for scanning transmission electron microscopy

Position dependence of the visibility of a single gold atom in silicon crystals in haadf-stem image simulation

Observation apparatus and observation method using an electron beam

Bio electron microscope and observation method of specimen