scholarly journals Direct observations of atomic structures of defects in GaN by high-resolution Z-contrast STEM

1997 ◽  
Author(s):  
Y. Xin ◽  
S.J. Pennycook ◽  
N.D. Browning ◽  
S. Sivananthan ◽  
P.D. Nellist ◽  
...  
Keyword(s):  
High Resolution ◽  
Atomic Structures ◽  
Direct Observations ◽  
Z Contrast

scholarly journals Direct Observations Of Atomic Structures Of Defects In Gan By High Resolution Z-Contrast Stem

1997 ◽  
Vol 482 ◽  
Author(s):  
Y. Xin ◽  
S.J. Pennycook ◽  
N.D. Browning ◽  
P. D. Nellist ◽  
S. Sivananthan ◽  
...  
Keyword(s):  
High Resolution ◽  
Direct Observation ◽  
Stacking Fault ◽  
Threading Dislocation ◽  
Contrast Imaging ◽  
Atomic Core ◽  
Atomic Structures ◽  
Direct Observations ◽  
Z Contrast ◽  
Contrast Image

AbstractGaN/(0001)Sapphire grown by low pressure MOVPE is studied by high resolution Z-contrast imaging using STEM. First direct observation of the threading dislocation with edge character shows the atomic core structure, which appears to have a similar configuration to the {10–10} surface. The surfaces of the nanopipe walls are on {10–10} with the terminating layer between the atoms with one bond per pair. In addition, the high resolution Z-contrast image of the prismatic stacking fault confirms the results by conventional HRTEM.

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.

High-Resolution Image Simulation of a Tilted Crystal

1990 ◽  
Vol 48 (1) ◽  
pp. 68-69
Author(s):  
C. J. D. Hetherington
Keyword(s):  
High Resolution ◽  
Crystal Thickness ◽  
Thin Specimen ◽  
Atomic Structures ◽  
Kikuchi Lines ◽  
High Resolution Images ◽  
Final Estimate ◽  
Simulated Images ◽  
Habit Planes

Most high resolution images are not directly interpretable but must be compared with simulations based on model atomic structures and appropriate imaging conditions. Typically, the only parameters that are adjusted, in addition to the structure models, are crystal thickness and microscope defocus. Small tilts of the crystal away from the exact zone axis have only rarely been considered. It is shown here that, in the analysis of an image of a silicon twin intersection, the crystal tilt could be accurately estimated and satisfactorily included in the simulations.The micrograph shown in figure 1 was taken as part of an HREM study of indentation-induced hexagonal silicon. In this instance, the intersection of two twins on different habit planes has driven the silicon into hexagonal stacking. However, in order to confirm this observation, and in order to investigate other defects in the region, it has been necessary to simulate the image taking into account the very apparent crystal tilt. The inability to orientate the specimen at the exact [110] zone was influenced by i) the buckling of the specimen caused by strains at twin intersections, ii) the absence of Kikuchi lines or a clearly visible Laue circle in the diffraction pattern of the thin specimen and iii) the avoidance of radiation damage (which had marked effects on images taken a few minutes later following attempts to realign the crystal.) The direction of the crystal tilt was estimated by observing which of the {111} planes remained close to edge-on to the beam and hence strongly imaged. Further refinement of the direction and magnitude of the tilt was done by comparing simulated images to experimental images in a through-focal series. The presence of three different orientations of the silicon lattice aided the unambiguous determination of the tilt. The final estimate of a 0.8° tilt in the 200Å thick specimen gives atomic columns a projected width of about 3Å.

Combined Experimentaland Theoretical Determination of the Atomic Structure of the (310) Twin in NB

1991 ◽  
Vol 238 ◽  
Author(s):  
Geoffrey H. Campbells ◽  
Wayne E. King ◽  
Stephen M. Foiles ◽  
Peter Gumbsch ◽  
Manfred Rühle
Keyword(s):  
High Resolution ◽  
Theoretical Models ◽  
High Resolution Electron Microscopy ◽  
Interatomic Potentials ◽  
Image Simulation ◽  
Theoretical Determination ◽  
Atomic Structures ◽  
Resolution Electron ◽  
High Resolution Images

ABSTRACTA (310) twin boundary in Nb has been fabricated by diffusion bonding oriented single crystals and characterized using high resolution electron microscopy. Atomic structures for the boundary have been predicted using different interatomic potentials. Comparison of the theoretical models to the high resolution images has been performed through image simulation. On the basis of this comparison, one of the low energy structures predicted by theory can be ruled out.

scholarly journals Direct Observations of High Resolution 1H NMR in Liquid Phase for Peptides bound to Bicelles

2003 ◽  
Vol 60 (4) ◽  
pp. 199-202 ◽  
Author(s):  
Ken KAWAGUCHI ◽  
Kazuo KIMURA ◽  
Tetsuo ASAKURA
Keyword(s):  
Liquid Phase ◽  
High Resolution ◽  
1H Nmr ◽  
Direct Observations

High Resolution Lattice Images of G.P.Zones and Solute Clusters in Al-Cu and Cu-Be Alloys

1982 ◽  
Vol 21 ◽  
Author(s):  
H. Yoshida ◽  
H. Hashimoto ◽  
Y. Yokota ◽  
M. Takeda
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Atomic Structures ◽  
Resolution Electron ◽  
Microscope Images ◽  
Lattice Images ◽  
Lattice Planes

ABSTRACTAtomic structures of G.P. zones and solute clusters in Al-Cu and Cu-Be alloys are studied by the atom resolution electron microscope images. The images of plate-like G.P. zones appear as dotted images with various brightnesses along (200) lattice planes. The solute clusters are also observed along (111) lattice planes.

Evaluation of high-quality image reconstruction techniques applied to high-resolution Z-contrast imaging

2017 ◽  
Vol 182 ◽  
pp. 283-291 ◽  
Author(s):  
G. Bárcena-González ◽  
M.P. Guerrero-Lebrero ◽  
E. Guerrero ◽  
A. Yañez ◽  
D. Fernández-Reyes ◽  
...  
Keyword(s):  
High Resolution ◽  
Image Reconstruction ◽  
Contrast Imaging ◽  
High Quality ◽  
Image Reconstruction Techniques ◽  
High Quality Image ◽  
Quality Image ◽  
Z Contrast

Atomic Structures of Oxygen-associated Defects in Sintered Aluminum Nitride Ceramics

1999 ◽  
Vol 5 (5) ◽  
pp. 352-357 ◽  
Author(s):  
Yanfa Yan ◽  
S. J. Pennycook ◽  
M. Terauchi ◽  
M. Tanaka
Keyword(s):  
Stacking Sequence ◽  
Contrast Imaging ◽  
Octahedral Layer ◽  
Atomic Structures ◽  
Inversion Domain ◽  
Sintered Aluminum ◽  
Domain Boundaries ◽  
Convergent Beam ◽  
Z Contrast ◽  
Inversion Domain Boundaries

Convergent-beam electron diffraction and Z-contrast imaging are used to study oxygen-associated defects, flat inversion domain boundaries, dislocations, and interfaces in sintered AlN ceramics. The structures of these defects are directly derived from atomic-resolution Z-contrast images. The flat inversion domain boundaries contain a single Al-O octahedral layer and have a stacking sequence of . . .bAaB-bAc-CaAc. . , where -cAb- indicates the single octahedral layer. The expansion at the flat inversion domain boundaries is measured to be 0.06 (±0.02) nm. The interfaces between 2H- and polytypoid-AlN are found to be also inversion domain boundaries but their stacking sequence differs from that of the flat inversion domain boundaries.

Sign in / Sign up

Export Citation Format

Share Document