Direct Imaging of Ordering in Si-Ge Alloys, Ultrathin Superlattices, and Buried Ge Layers

1991 ◽  
Vol 220 ◽  
Author(s):  
D. E. Jesson ◽  
S. J. Pennycook ◽  
J. -M. Baribeau
Keyword(s):  
Long Range ◽  
Imaging Studies ◽  
Contrast Imaging ◽  
Direct Imaging ◽  
Mbe Growth ◽  
Nonequilibrium Growth ◽  
Pump Mechanism ◽  
Z Contrast ◽  
Lateral Segregation

ABSTRACTWe review recent Z-contrast imaging studies of Si-Ge ultrathin superlattices, alloys, and buried Ge layers. It is found that whenever Si is deposited onto a Ge (2 × 1) surface, Ge is pumped into the growing Si layer, and this is accompanied by interfacial ordering. This is explained by a novel Ge atom pump mechanism which occurs during MBE growth. Codeposition and alloy growth results in long range (111) ordering as a consequence of lateral segregation during nonequilibrium growth.

Step-Driven Surface Segregation and Ordering During Si-Ge MBE Growth

1992 ◽  
Vol 263 ◽  
Author(s):  
D. E. Jesson ◽  
S. J. Pennycook ◽  
J.-M. Baribeau ◽  
D. C. Houghton
Keyword(s):  
Surface Segregation ◽  
Ordered Structure ◽  
Mbe Growth ◽  
Vertical Segregation ◽  
Z Contrast ◽  
Lateral Segregation ◽  
Phase Variants ◽  
Step Edges

ABSTRACTAn important role of type SB step edges in determining the as-grown microstructure of Si-Ge superlattices and alloys is implicated from direct Z-contrast images of as-grown structures. A variety of different ordered phase variants can arise at each Si on Ge interface as a result of vertical segregation during superlattice growth. A new monoclinic-ordered structure is predicted to arise as a result of lateral segregation during alloy growth.

New insights into nanostructure and geochemistry of bioapatite in REE-rich deep-sea sediments: LA-ICP-MS, TEM, and Z-contrast imaging studies

2019 ◽  
Vol 512 ◽  
pp. 58-68 ◽  
Author(s):  
Jianlin Liao ◽  
Xiaoming Sun ◽  
Dengfeng Li ◽  
Rina Sa ◽  
Yang Lu ◽  
...  
Keyword(s):  
Deep Sea ◽  
Imaging Studies ◽  
Contrast Imaging ◽  
Icp Ms ◽  
Deep Sea Sediments ◽  
Z Contrast

High Resolution Z-Contrast Imaging and Lattice Location Analysis of Dopants in Ion-Implanted Silicon

1984 ◽  
Vol 41 ◽  
Author(s):  
S. J. Pennycook ◽  
J. Narayan ◽  
R. J. Cijlbertson ◽  
E. Fogarassy ◽  
P. E. Batson
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Spatial Resolution ◽  
Location Analysis ◽  
Contrast Imaging ◽  
Direct Imaging ◽  
Dopant Segregation ◽  
Z Contrast ◽  
Microscopy Techniques

AbstractTwo new electron microscopy techniques have been developed which greatly extend the capabilities for the micro-characterization of semiconductors. The first is a technique for the direct imaging of dopants in semiconductors, whether or not they are in solution, using Z-contrast, and the second is a technique for determining the substitutional fraction of dopant. Both techniques are capable of nanometer spatial resolution and allow the detailed study of dopant segregation, precipitation, and clustering effects.

Complementary Z-Contrast Imaging and Digital Image Processing

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.

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

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,

High-resolution z-contrast imaging of semiconductor interfaces

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.

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

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.

scholarly journals Nanoscale bubble domains with polar topologies in bulk ferroelectrics

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.

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

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.

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

1994 ◽  
Vol 175 (1) ◽  
pp. 10-20 ◽  
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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