Automatic analysis of Kikuchi diffraction patterns

Recent advances in the automatic indexing of backscatter Kikuchi diffraction patterns on the scanning electron microscope (SEM) has resulted in the development of a new type of microscopy. The ability to obtain statistically relevant information on the spatial distribution of crystallite orientations is giving rise to new insight into polycrystalline microstructures and their relation to materials properties. A limitation of the technique in the SEM is that the spatial resolution of the measurement is restricted by the relatively large size of the electron beam in relation to various microstructural features. Typically the spatial resolution in the SEM is limited to about half a micron or greater. Heavily worked structures exhibit microstructural features much finer than this and require resolution on the order of nanometers for accurate characterization. Transmission electron microscope (TEM) techniques offer sufficient resolution to investigate heavily worked crystalline materials.Crystal lattice orientation determination from Kikuchi diffraction patterns in the TEM (Figure 1) requires knowledge of the relative positions of at least three non-parallel Kikuchi line pairs in relation to the crystallite and the electron beam.

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Nanoscale Automated Phase and Orientation Mapping in the TEM

Microscopy Today ◽

10.1017/s1551929512000818 ◽

2012 ◽

Vol 20 (6) ◽

pp. 38-42 ◽

Cited By ~ 12

Author(s):

A. D. Darbal ◽

M. Gemmi ◽

J. Portillo ◽

E. Rauch ◽

S. Nicolopoulos

Keyword(s):

Electron Beam ◽

Electron Microscope ◽

Spatial Resolution ◽

Nanocrystalline Materials ◽

Template Matching ◽

Electron Backscattered Diffraction ◽

Orientation Imaging ◽

Transmission Electron ◽

Orientation Mapping ◽

Diffraction Patterns

The limitation of spatial resolution in orientation imaging via electron backscattered diffraction analysis in the scanning electron microscope (SEM) makes it difficult to investigate the microstructure of nanocrystalline materials. The use of the recently developed transmission electron microscope (TEM) based product, known as ASTAR, offers the possibility of reliable orientation/phase mapping with a spatial resolution below 3 nm. In ASTAR, a nanoprobe electron beam is scanned over the specimen, and spot diffraction patterns are collected. The electron beam is precessed to reduce dynamical effects and improve pattern quality. Using template matching, the diffraction patterns are indexed automatically.

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Annealing Effects in Ten Films of Thoria

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100101712 ◽

1968 ◽

Vol 26 ◽

pp. 392-393

Author(s):

S. E. Bronisz ◽

Dana L. Douglass

Keyword(s):

Electron Microscopy ◽

Thin Films ◽

Transmission Electron Microscopy ◽

Electron Beam ◽

Electron Microscope ◽

Single Crystals ◽

Crystalline Materials ◽

Transmission Electron ◽

Annealing Effects ◽

Diffraction Effects

Thin films of thoria, either cleaved from air-fired material or vacuum deposited on polished copper substrates, were examined by transmission electron microscopy. As prepared, the two types of samples were considerably different, but after being heated in the electron microscope they were closely similar.The cleaved samples were obtained by means of extraction replication of fracture surfaces of polycrystalline thoria. The thin flakes ranged from about 0.1 to 20 μm in diameter. Most of them were single crystals exhibiting the diffraction effects expected of crystalline materials and containing many long dislocations. Upon heating with the unapertured electron beam the dislocations disappeared, the crystals became more electron transparent, and the striated microstructure shown in Fig. 1 developed. The orientations of most of the cleaved crystals were equally divided among ﹛110﹜, ﹛111﹜, and ﹛112﹜. The striae were usually parallel to <110> or <135>.

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The Structure and Texture of Y2O3:Tb Nanocrystals

MRS Proceedings ◽

10.1557/proc-452-395 ◽

1996 ◽

Vol 452 ◽

Author(s):

J. Taylor ◽

M. Libera ◽

E. Goldburt ◽

R. Bhargava

Keyword(s):

Electron Beam ◽

Electron Microscope ◽

Electron Diffraction ◽

Selected Area Electron Diffraction ◽

Incident Electron Beam ◽

Transmission Electron ◽

Cubic Structure ◽

Diffraction Patterns ◽

Electron Energy Loss ◽

Microstructural Studies

AbstractThis paper presents the results of microstructural studies of terbium-doped yttria quantum nanocrystals by imaging and diffraction in a transmission electron microscope. The nanocrystals are typically found in clusters of varying size. Electron energy-loss spectroscopy confirms that the particles consist of yttrium and oxygen. Analysis of selected-area electron diffraction patterns shows that the nanocrystals largely have the cubic structure found in bulk yttria. These patterns furthermore suggest that within each cluster the nanocrystals align themselves with a preferred orientation relative to the incident electron beam as well as to each other.

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Aspects of microanalysis in a transmission electron microscope

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100109690 ◽

1978 ◽

Vol 36 (1) ◽

pp. 510-511

Author(s):

R. Sinclair ◽

B.E. Jacobson

Keyword(s):

Grain Size ◽

Electron Beam ◽

Electron Microscope ◽

Chemical Analysis ◽

Transmission Electron Microscope ◽

Vapor Deposition ◽

Critical Currents ◽

X Ray ◽

Fine Grain ◽

Transmission Electron

INTRODUCTIONThe prospect of performing chemical analysis of thin specimens at any desired level of resolution is particularly appealing to the materials scientist. Commercial TEM-based systems are now available which virtually provide this capability. The purpose of this contribution is to illustrate its application to problems which would have been intractable until recently, pointing out some current limitations.X-RAY ANALYSISIn an attempt to fabricate superconducting materials with high critical currents and temperature, thin Nb3Sn films have been prepared by electron beam vapor deposition [1]. Fine-grain size material is desirable which may be achieved by codeposition with small amounts of Al2O3 . Figure 1 shows the STEM microstructure, with large (∽ 200 Å dia) voids present at the grain boundaries. Higher quality TEM micrographs (e.g. fig. 2) reveal the presence of small voids within the grains which are absent in pure Nb3Sn prepared under identical conditions. The X-ray spectrum from large (∽ lμ dia) or small (∽100 Ǻ dia) areas within the grains indicates only small amounts of A1 (fig.3).

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Deviations from Ideal Decagonal Symmetry in Electron Diffraction Patterns of the “Decagonal” Phase in the Al-Co-Cu Alloy System

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100088889 ◽

1991 ◽

Vol 49 ◽

pp. 914-915

Author(s):

Atul S. Ramani ◽

Earle R. Ryba ◽

Paul R. Howell

Keyword(s):

Electron Microscope ◽

Alloy System ◽

Nominal Composition ◽

Dimensional Lattice ◽

3 Dimensional ◽

Decagonal Phase ◽

Cu Alloy ◽

Transmission Electron ◽

Lattice Periodicity ◽

Diffraction Patterns

The “decagonal” phase in the Al-Co-Cu system of nominal composition Al65CO15Cu20 first discovered by He et al. is especially suitable as a topic of investigation since it has been claimed that it is thermodynamically stable and is reported to be periodic in the dimension perpendicular to the plane of quasiperiodic 10-fold symmetry. It can thus be expected that it is an important link between fully periodic and fully quasiperiodic phases. In the present paper, we report important findings of our transmission electron microscope (TEM) study that concern deviations from ideal decagonal symmetry of selected area diffraction patterns (SADPs) obtained from several “decagonal” phase crystals and also observation of a lattice of main reflections on the 10-fold and 2-fold SADPs that implies complete 3-dimensional lattice periodicity and the fundamentally incommensurate nature of the “decagonal” phase. We also present diffraction evidence for a new transition phase that can be classified as being one-dimensionally quasiperiodic if the lattice of main reflections is ignored.

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Effects of High-Energy Ions on Synthetic Quartz

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100095972 ◽

1972 ◽

Vol 30 ◽

pp. 544-545

Author(s):

Joseph J. Comer ◽

Charles Bergeron ◽

Lester F. Lowe

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Electron Beam ◽

High Energy ◽

Transmission Electron ◽

Kikuchi Lines ◽

High Energy Ions ◽

Diffraction Patterns ◽

Dauphiné Twinning ◽

Beam Damage

Using a Van De Graaff Accelerator thinned specimens were subjected to bombardment by 3 MeV N+ ions to fluences ranging from 4x1013 to 2x1016 ions/cm2. They were then examined by transmission electron microscopy and reflection electron diffraction using a 100 KV electron beam.At the lowest fluence of 4x1013 ions/cm2 diffraction patterns of the specimens contained Kikuchi lines which appeared somewhat broader and more diffuse than those obtained on unirradiated material. No damage could be detected by transmission electron microscopy in unannealed specimens. However, Dauphiné twinning was particularly pronounced after heating to 665°C for one hour and cooling to room temperature. The twins, seen in Fig. 1, were often less than .25 μm in size, smaller than those formed in unirradiated material and present in greater number. The results are in agreement with earlier observations on the effect of electron beam damage on Dauphiné twinning.

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Slow-Scan CCD Observation of Backscattering Patterns in SEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100131176 ◽

1992 ◽

Vol 50 (2) ◽

pp. 1308-1309

Author(s):

F. Ouyang ◽

D. A. Ray ◽

O. L. Krivanek

Keyword(s):

Electron Beam ◽

Electron Microscope ◽

Scanning Electron Microscope ◽

Dynamic Range ◽

High Sensitivity ◽

Lens System ◽

Wide Dynamic Range ◽

Peltier Cooler ◽

Diffraction Patterns ◽

Scanning Electron

Electron backscattering Kikuchi diffraction patterns (BKDP) reveal useful information about the structure and orientation of crystals under study. With the well focused electron beam in a scanning electron microscope (SEM), one can use BKDP as a microanalysis tool. BKDPs have been recorded in SEMs using a phosphor screen coupled to an intensified TV camera through a lens system, and by photographic negatives. With the development of fiber-optically coupled slow scan CCD (SSC) cameras for electron beam imaging, one can take advantage of their high sensitivity and wide dynamic range for observing BKDP in SEM.We have used the Gatan 690 SSC camera to observe backscattering patterns in a JEOL JSM-840A SEM. The CCD sensor has an active area of 13.25 mm × 8.83 mm and 576 × 384 pixels. The camera head, which consists of a single crystal YAG scintillator fiber optically coupled to the CCD chip, is located inside the SEM specimen chamber. The whole camera head is cooled to about -30°C by a Peltier cooler, which permits long integration times (up to 100 seconds).

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Modern TEM systems architecture

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100144486 ◽

1986 ◽

Vol 44 ◽

pp. 602-605

Author(s):

U. Gross ◽

P. Hagemann

Keyword(s):

Electron Microscope ◽

Information Gathering ◽

Systems Architecture ◽

Control Functions ◽

Transmission Electron ◽

New Information ◽

Comprehensive Information ◽

Scanning Transmission ◽

Diffraction Patterns ◽

Analytical Equipment

By addition of analytical equipment, scanning transmission accessories and data processing equipment the basic transmission electron microscope (TEM) has evolved into a comprehensive information gathering system. This extension has led to increased complexity of the instrument as compared with the straightforward imaging microscope, since in general new information capacity has required the addition of new control hardware. The increased operational complexity is reflected in a proliferation of knobs and buttons.In the conventional electron microscope design the operating panel of the instrument has distinct control elements to alter optical conditions of the microscope column in different modes. As a consequence a multiplicity of control functions has been inevitable. Examples of this are the three pairs of focus and magnification controls needed for TEM imaging, diffraction patterns, and STEM images.

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A Structural Model for a Quasi-Crystalline Material Derived from TEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100178999 ◽

1990 ◽

Vol 48 (1) ◽

pp. 48-49

Author(s):

Jan-Olov Bovin ◽

Osamu Terasaki ◽

Jan-Olle Malm ◽

Sven Lidin ◽

Sten Andersson

Keyword(s):

High Resolution ◽

Electron Diffraction ◽

Structural Model ◽

Image Intensifier ◽

Crystalline Materials ◽

Icosahedral Phases ◽

Transmission Electron ◽

Electron Microscopes ◽

Diffraction Patterns ◽

Quasi Crystals

High resolution transmission electron microscopy (HRTEM) is playing an important role in identifying the new icosahedral phases. The selected area diffraction patterns of quasi crystals, recorded with an aperture of the radius of many thousands of Ångströms, consist of dense arrays of well defined sharp spots with five fold dilatation symmetry which makes the interpretation of the diffraction process and the resulting images different from those invoked for usual crystals. The atomic structure of the quasi crystals is not established even if several models are proposed. The correct structure model must of course explain the electron diffraction patterns with 5-, 3- and 2-fold symmetry for the phases but it is also important that the HRTEM images of the alloys match the computer simulated images from the model. We have studied quasi crystals of the alloy Al65Cu20Fe15. The electron microscopes used to obtain high resolution electro micrographs and electron diffraction patterns (EDP) were a (S)TEM JEM-2000FX equipped with EDS and PEELS showing a structural resolution of 2.7 Å and a IVEM JEM-4000EX with a UHP40 high resolution pole piece operated at 400 kV and with a structural resolution of 1.6 Å. This microscope is used with a Gatan 622 TV system with an image intensifier, coupled to a YAG screen. It was found that the crystals of the quasi crystalline materials here investigated were more sensitive to beam damage using 400 kV as electron accelerating voltage than when using 200 kV. Low dose techniques were therefore applied to avoid damage of the structure.

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