Measuring local lattice polarity in AlN and GaN by high resolution Z-contrast imaging: The case of (0001) and (11¯00) GaN quantum dots

2008 ◽  
Vol 92 (20) ◽  
pp. 201904 ◽  
Author(s):  
Jean-Luc Rouviere ◽  
Catherine Bougerol ◽  
Benoit Amstatt ◽  
Edith Bellet-Almaric ◽  
Bruno Daudin
Keyword(s):  
Quantum Dots ◽  
High Resolution ◽  
Contrast Imaging ◽  
Local Lattice ◽  
Z Contrast

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.

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

Simulation and Quantification of High-Resolution Z-Contrast Imaging of Semiconductor Interfaces

1989 ◽  
Vol 159 ◽  
Author(s):  
D. E. Jesson ◽  
S. J. Pennycook ◽  
M. F. Chisholm
Keyword(s):  
High Resolution ◽  
Cross Section ◽  
Image Interpretation ◽  
Bloch Wave ◽  
Small Computer ◽  
High Angle ◽  
Contrast Imaging ◽  
Resolution Function ◽  
Semiconductor Interfaces ◽  
Z Contrast

ABSTRACTIncoherent characteristics of Z-contrast STEM images are explained using a Bloch wave approach. To a good approximation, the image is given by the columnar high-angle cross-section multiplied by the s-state intensity at the projected atom sites, convoluted with an appropriate resolution function. Consequently, image interpretation can be performed intuitively and quantitative simulation can be implemented on a small computer. The feasibility of ‘column-by-column’ compositional mapping is discussed.

scholarly journals Direct observation of threading dislocations in GaN by high-resolution Z-contrast imaging

1998 ◽  
Author(s):  
Y. Xin ◽  
N.D. Browning ◽  
S. Sivananthan ◽  
S.J. Pennycook ◽  
P.D. Nellist ◽  
...  
Keyword(s):  
High Resolution ◽  
Direct Observation ◽  
Threading Dislocations ◽  
Contrast Imaging ◽  
Z Contrast

Z-Contrast Imaging of Heavy Metal Particles Supported in A Zeolitic Matrix Via High-Resolution Stem

1987 ◽  
Vol 45 ◽  
pp. 204-205
Author(s):  
J. H. Butler ◽  
G. M. Brown
Keyword(s):  
High Resolution ◽  
Incident Beam ◽  
Dark Field ◽  
Irradiation Damage ◽  
Contrast Imaging ◽  
Vacuum Oven ◽  
Annular Dark Field ◽  
Resolution Imaging ◽  
Beam Currents ◽  
Z Contrast

High resolution Imaging of zeolites is difficult because these materials are very susceptible to Irradiation damage. It is now well known that dehydrated samples are more stable under the electron beam. Thus the most successful high resolution studies of zeolites to date have been on samples which were freeze-fractured and subsequently dehydrated via heating in a vacuum oven. Electron microscopy was then performed using a combination of low Incident beam currents and sensitive detectors. One problem with this method is that zeolites fracture along cleavage planes and therefore are deposited on microscope grids In a particular orientation. This limits the range of viewing angles. Here we describe a method of sample preparation via ultramlctrotomy as well as the establishment of suitable FEG/STEM Imaging conditions which permit the observation of small (7-14 A diameter) Pt particles within Individual zeolite channels using the method of Z-contrast as applied with a high-angle annular dark field detector. This method allows observation over all crystalline orientations for relatively long exposures to the beam.

Bulk interfaces in a Ni-rich Ni–Au alloy investigated by high-resolution Z-contrast imaging

Micron ◽  
2004 ◽  
Vol 35 (8) ◽  
pp. 695-700 ◽  
Author(s):  
M.J Portmann ◽  
R Erni ◽  
H Heinrich ◽  
G Kostorz
Keyword(s):  
High Resolution ◽  
Contrast Imaging ◽  
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.

scholarly journals Atomic Scale Structure and Chemistry of Interfaces by Z-Contrast Imaging and Electron Energy Loss Spectroscopy in the Stem

1994 ◽  
Vol 341 ◽  
Author(s):  
M. M. McGibbon ◽  
N. D. Browning ◽  
M. F. Chisholm ◽  
A. J. McGibbon ◽  
S. J. Pennycook ◽  
...  
Keyword(s):  
High Resolution ◽  
Energy Loss ◽  
Electron Energy ◽  
Atomic Structure ◽  
Electron Energy Loss Spectroscopy ◽  
Atomic Scale ◽  
Chemical Information ◽  
Contrast Imaging ◽  
Z Contrast ◽  
Electron Energy Loss

AbstractThe macroscopic properties of many materials are controlled by the structure and chemistry at grain boundaries. A basic understanding of the structure-property relationship requires a technique which probes both composition and chemical bonding on an atomic scale. High-resolution Z-contrast imaging in the scanning transmission electron microscope (STEM) forms an incoherent image in which changes in atomic structure and composition across an interface can be interpreted directly without the need for preconceived atomic structure models (1). Since the Z-contrast image is formed by electrons scattered through high angles, parallel detection electron energy loss spectroscopy (PEELS) can be used simultaneously to provide complementary chemical information on an atomic scale (2). The fine structure in the PEEL spectra can be used to investigate the local electronic structure and the nature of the bonding across the interface (3). In this paper we use the complimentary techniques of high resolution Zcontrast imaging and PEELS to investigate the atomic structure and chemistry of a 25° symmetric tilt boundary in a bicrystal of the electroceramic SrTiO3.

Z-Contrast Imaging of Grain-Boundary Core Structures in Semiconductors

MRS Bulletin ◽  
1997 ◽  
Vol 22 (8) ◽  
pp. 53-57 ◽  
Author(s):  
M.F. Chisholm ◽  
S.J. Pennycook
Keyword(s):  
High Resolution ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Phase Contrast ◽  
Atomic Scale ◽  
Resolving Power ◽  
Boundary Structure ◽  
Contrast Imaging ◽  
Contrast Technique ◽  
Z Contrast

Interest in semiconductor grain boundaries relates to the development of polycrystalline materials for photovoltaics and integrated-circuit interconnects. Although these structures are responsible for deleterious electrical effects, there are few experimental techniques available to study them at the required atomic scale. Therefore models of the physical processes occurring at grain boundaries have necessarily taken a macroscopic approach. Fortunately recent developments have resulted in tools that provide unprecedented glimpses into these interfaces and that will allow us to address anew the connection between grain-boundary structure and properties.Z-Contrast ImagingWhen exploring the unknown, we rely heavily on our eyes (incoherent imaging) to provide a direct image of a new object. In order to explore the unforeseen atomic configurations present at extended defects in materials, it again would be desirable if one could obtain a directly interpretable image of the unfamiliar structures present in the defect cores. Z-contrast electron microscopy provides such a view with both atomic resolution and compositional sensitivity.This high-resolution imaging technique differs from conventional high-resolution phase-contrast imaging. The phase-contrast technique produces a coherent image, an interference pattern formed by recombining the waves diffracted by the specimen. In the Z-contrast technique, the image is incoherent; it is essentially a map of the scattering power of the specimen. Additionally as was first determined by Lord Rayleigh, the incoherent mode of image formation has double the resolving power of the coherent mode.

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