Z-contrast Imaging of Incommensurately Modulated Structure in Plagioclase Feldspars

Plagioclase feldspars are the most abundant mineral in the Earth&#8217;s crust. Intermediate plagioclase feldspars commonly display incommensurately modulated structure or aperiodic structure. Both fast-cooled and slow-cooled plagioclase feldspars display the incommensurately modulated structures. The ordering pattern in the incommensurately modulated structures of e-plagioclase (characterized by the satellite diffraction peak called e-reflections) are the most complicated and intriguing. The modulated structure has a superspace group symmetry of X-1(&#945;&#946;&#947;)0 with a special centering condition of (&#189; &#189; &#189; 0), (0 0 &#189; &#189;), (&#189; &#189; 0 &#189;), and the q-vector has components (i.e., &#948;h, &#948;k, &#948;l) along all three axes in reciprocal space. Displacive modulation, occupational modulation, and density modulation are observed in slowly cooled labradorite feldspars. Z-contrast images show both Ca-Na ordering and density modulation. Local structure of lamellae domains has I1 symmetry. The neighboring lamellae domains are in inversion twinning relationship.&#160; The results from Z-contrast imaging and low-temperature single XRD provide consistent structure with density modulation. &#160;The amplitudes of the modulation waves are new parameters for quantifying the ordering state of plagioclase feldspars. Iridescent labradorite feldspars display exsolution lamellae with average periodicity ranging from ~ 150 nm to ~350 nm. Compositional difference between the lamellae is about 10 to 15 mole % in anorthite component. Areas or zones with red iridescent color (i.e., long lamellae periodicity) always contain more Ca (~ 1 to 3 mole %) than the areas with blue (or green) iridescent color within the same labradorite crystal.&#160; We proposed that the solvus for B&#248;ggild intergrowth has a loop-like shape ranging from ~An44 to ~ An63. The Ca-rich side has higher temperature than the Na-rich side. The shapes of satellite peaks, the distances between e-reflections (modulation periods), and even the intensity of c-reflections may also be used evaluate the ordering state or cooling rate of the plagioclase feldspar. Both modulated structure and the exsolution lamellae can be used as proxies for quantifying cooling rate of a labradorite and its host rock.

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Complementary Z-Contrast Imaging and Digital Image Processing

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100118394 ◽

1985 ◽

Vol 43 ◽

pp. 304-305

Author(s):

K. N. Colonna ◽

G. Oliphant

Keyword(s):

Image Processing ◽

Heavy Metal ◽

Digital Image Processing ◽

Digital Image ◽

Biological Tissue ◽

Biological Imaging ◽

Tissue Preparation ◽

Contrast Imaging ◽

Imaging Tool ◽

Z Contrast

Harmonious use of Z-contrast imaging and digital image processing as an analytical imaging tool was developed and demonstrated in studying the elemental constitution of human and maturing rabbit spermatozoa. Due to its analog origin (Fig. 1), the Z-contrast image offers information unique to the science of biological imaging. Despite the information and distinct advantages it offers, the potential of Z-contrast imaging is extremely limited without the application of techniques of digital image processing. For the first time in biological imaging, this study demonstrates the tremendous potential involved in the complementary use of Z-contrast imaging and digital image processing.Imaging in the Z-contrast mode is powerful for three distinct reasons, the first of which involves tissue preparation. It affords biologists the opportunity to visualize biological tissue without the use of heavy metal fixatives and stains. For years biologists have used heavy metal components to compensate for the limited electron scattering properties of biological tissue.

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Atomic resolution Z-contrast imaging of bulk crystal surfaces in Scanning Reflection Electron Microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010017520x ◽

1990 ◽

Vol 48 (4) ◽

pp. 414-415

Author(s):

Z. L. Wang ◽

J. Bentley

Keyword(s):

Electron Microscopy ◽

Elastic Scattering ◽

Dark Field ◽

Contrast Imaging ◽

Crystal Lattices ◽

Small Probe ◽

Scanning Transmission ◽

Annular Dark Field ◽

Image Position ◽

Z Contrast

The success of obtaining atomic-number-sensitive (Z-contrast) images in scanning transmission electron microscopy (STEM) has shown the feasibility of imaging composition changes at the atomic level. This type of image is formed by collecting the electrons scattered through large angles when a small probe scans across the specimen. The image contrast is determined by two scattering processes. One is the high angle elastic scattering from the nuclear sites,where ϕNe is the electron probe function centered at bp = (Xp, yp) after penetrating through the crystal; F denotes a Fourier transform operation; D is the detection function of the annular-dark-field (ADF) detector in reciprocal space u. The other process is thermal diffuse scattering (TDS), which is more important than the elastic contribution for specimens thicker than about 10 nm, and thus dominates the Z-contrast image. The TDS is an average “elastic” scattering of the electrons from crystal lattices of different thermal vibrational configurations,

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High-resolution z-contrast imaging of semiconductor interfaces

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100154317 ◽

1989 ◽

Vol 47 ◽

pp. 468-469

Author(s):

S. J. Pennycook

Keyword(s):

High Resolution ◽

Phase Contrast ◽

Contrast Imaging ◽

Compositional Modulation ◽

Semiconductor Interfaces ◽

Complex Figure ◽

Thin Region ◽

Stem Image ◽

Annular Detector ◽

Z Contrast

Using a high-angle annular detector on a high-resolution STEM it is possible to form incoherent images of a crystal lattice characterized by strong atomic number or Z contrast. Figure 1 shows an epitaxial Ge film on Si(100) grown by oxidation of Ge-implanted Si. The image was obtained using a VG Microscopes' HB501 STEM equipped with an ultrahigh resolution polepiece (Cs ∽1.2 mm, demonstrated probe FWHM intensity ∽0.22 nm). In both crystals the lattice is resolved but that of Ge shows much brighter allowing the interface to be located exactly and interface steps to be resolved (arrowed). The interface was indistinguishable in the phase-contrast STEM image from the same region, and even at higher resolution the location of the interface is complex. Figure 2 shows a thin region of an MBE-grown ultrathin super-lattice (Si8Ge2)100. The expected compositional modulation would show as one bright row of dots from the 2 Ge monolayers separated by 4 rows of lighter Si columns. The image shows clearly that strain-induced interdiffusion has occurred on the monolayer scale.

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Quantitative structure determination of interfaces through Z-contrast imaging and electron energy loss spectroscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100162983 ◽

1996 ◽

Vol 54 ◽

pp. 104-105

Author(s):

S. J. Pennycook ◽

P. D. Nellist ◽

N. D. Browning ◽

P. A. Langjahr ◽

M. Rühle

Keyword(s):

Grain Boundaries ◽

Cuprate Superconductors ◽

Structure Refinement ◽

3D Structure ◽

Real Space ◽

Contrast Imaging ◽

Coordination Polyhedra ◽

Burgers Vector ◽

Z Contrast ◽

Contrast Image

The simultaneous use of Z-contrast imaging with parallel detection EELS in the STEM provides a powerful means for determining the atomic structure of grain boundaries. The incoherent Z-contrast image of the high atomic number columns can be directly inverted to their real space arrangement, without the use of preconceived structure models. Positions and intensities may be accurately quantified through a maximum entropy analysis. Light elements that are not visible in the Z-contrast image can be studied through EELS; their coordination polyhedra determined from the spectral fine structure. It even appears feasible to contemplate 3D structure refinement through multiple scattering calculations.The power of this approach is illustrated by the recent study of a series of SrTiC>3 bicrystals, which has provided significant insight into some of the basic issues of grain boundaries in ceramics. Figure 1 shows the structural units deduced from a set of 24°, 36° and 65° symmetric boundaries, and 24° and 45° asymmetric boundaries. It can be seen that apart from unit cells and fragments from the perfect crystal, only three units are needed to construct any arbitrary tilt boundary. For symmetric boundaries, only two units are required, each having the same Burgers, vector of a<100>. Both units are pentagons, on either the Sr or Ti sublattice, and both contain two columns of the other sublattice, imaging in positions too close for the atoms in each column to be coplanar. Each column was therefore assumed to be half full, with the pair forming a single zig-zag column. For asymmetric boundaries, crystal geometry requires two types of dislocations; the additional unit was found to have a Burgers’ vector of a<110>. Such a unit is a larger source of strain, and is especially important to the transport characteristics of cuprate superconductors. These zig-zag columns avoid the problem of like-ion repulsion; they have also been seen in TiO2 and YBa2Cu3O7-x and may be a general feature of ionic materials.

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Nanoscale bubble domains with polar topologies in bulk ferroelectrics

Nature Communications ◽

10.1038/s41467-021-23863-w ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Jie Yin ◽

Hongxiang Zong ◽

Hong Tao ◽

Xuefei Tao ◽

Haijun Wu ◽

...

Keyword(s):

Physical Properties ◽

Bulk Material ◽

Condensed Matter ◽

Time Dependent ◽

Morphology Evolution ◽

Contrast Imaging ◽

Ferroelectric Films ◽

Modulated Phases ◽

Ferroelectric Memories ◽

Z Contrast

AbstractMultitudinous topological configurations spawn oases of many physical properties and phenomena in condensed-matter physics. Nano-sized ferroelectric bubble domains with various polar topologies (e.g., vortices, skyrmions) achieved in ferroelectric films present great potential for valuable physical properties. However, experimentally manipulating bubble domains has remained elusive especially in the bulk form. Here, in any bulk material, we achieve self-confined bubble domains with multiple polar topologies in bulk Bi0.5Na0.5TiO3 ferroelectrics, especially skyrmions, as validated by direct Z-contrast imaging. This phenomenon is driven by the interplay of bulk, elastic and electrostatic energies of coexisting modulated phases with strong and weak spontaneous polarizations. We demonstrate reversable and tip-voltage magnitude/time-dependent donut-like domain morphology evolution towards continuously and reversibly modulated high-density nonvolatile ferroelectric memories.

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Investigating Ca Segregated to a Grain Boundaries in MgO Using Multiple Scattering Analysis of Electron Energy Loss Spectra

Microscopy and Microanalysis ◽

10.1017/s1431927600024004 ◽

1998 ◽

Vol 4 (S2) ◽

pp. 776-777

Author(s):

J. P. Buban ◽

J. Zaborac ◽

H. Moltaji ◽

G. Duscher ◽

N. D. Browning

Keyword(s):

Energy Loss ◽

Grain Boundaries ◽

Electron Energy ◽

Structural Model ◽

Boundary Structure ◽

Structure Property ◽

Contrast Imaging ◽

Scale Properties ◽

Z Contrast ◽

Electron Energy Loss

Although grain boundaries typically account for only a small fraction of a material, they can have far reaching effects on the overall bulk scale properties. These effects are usually simply linked to the boundary having a different atomic arrangement to the bulk. A necessary first step in understanding the structure-property relationships is therefore a detailed determination of the boundary structure.One means of obtaining detailed information on the structure of grain boundaries is through correlated Z-contrast imaging and electron energy loss spectroscopy (EELS). The Z-contrast image generates a map of the grain boundary which can be used to position the probe in defined locations for spectroscopy. In the case of oxides, a structural model of the metal atom positions can be determined directly from the image. Furthermore, using a simple bond-valence sum minimization routine, the oxygen atoms can be placed so that the structure contains atoms that have valences consistent with their expected formal valence state.

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A novel method of Z-contrast imaging in STEM applied to double-labelling

Journal of Microscopy ◽

10.1111/j.1365-2818.1994.tb04783.x ◽

1994 ◽

Vol 175 (1) ◽

pp. 10-20 ◽

Cited By ~ 4

Author(s):

W. TICHELAAR ◽

C. FERGUSON ◽

J.-C. OLIVO ◽

K. R. LEONARD ◽

M. HAIDER

Keyword(s):

Double Labelling ◽

Contrast Imaging ◽

Novel Method ◽

Z Contrast

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Simultaneous atomic-resolution electron ptychography and Z-contrast imaging of light and heavy elements in complex nanostructures

Nature Communications ◽

10.1038/ncomms12532 ◽

2016 ◽

Vol 7 (1) ◽

Cited By ~ 103

Author(s):

H. Yang ◽

R. N. Rutte ◽

L. Jones ◽

M. Simson ◽

R. Sagawa ◽

...

Keyword(s):

Atomic Resolution ◽

Heavy Elements ◽

Contrast Imaging ◽

Resolution Electron ◽

Z Contrast ◽

Complex Nanostructures

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Synthesis and Structural Characterization of Ferromagnetic Au/Co Nanoparticles

MRS Proceedings ◽

10.1557/opl.2014.526 ◽

2014 ◽

Vol 1708 ◽

Cited By ~ 2

Author(s):

Nabraj Bhattarai ◽

Subarna Khanal ◽

Daniel Bahena ◽

Robert L. Whetten ◽

Miguel Jose-Yacaman

Keyword(s):

Quantum Interference ◽

Magnetic Measurements ◽

Ferromagnetic Behavior ◽

Contrast Imaging ◽

Uniform Size ◽

Transmission Electron ◽

Scanning Transmission ◽

Co Nanoparticles ◽

Z Contrast

ABSTRACTThe synthesis of bimetallic magnetic nanoparticles is very challenging because of the agglomeration and non-uniform size. In this paper, we present the synthesis of monodispersed 3-5 nm sized thiolated bimetallic alloyed Au/Co nanoparticles with decahedral and icosahedral shape, their characterization using Cs-corrected scanning transmission electron microscopy (STEM) and magnetic measurements using superconducting quantum interference device (SQUID) magnetometer. The Z-contrast imaging and energy dispersive X-ray spectroscopy (EDS) mapping showed an inhomogeneous alloying with minor segregation between Au and Co at nanoscale and the SQUID measurement exhibited the ferromagnetic behavior.

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