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Specimen charging on thin films with one conducting layer:Discussion of physical principles

Description: While the most familiar consequences of specimen charging in transmission electron microscopy can be eliminated by evaporating a thin conducting film (such as a carbon film) onto an insulating specimen, or by preparing samples directly on such a conducting film to begin with, a more subtle charging effect still remains. We argue here that specimen charging is in this case likely to produce a dipole sheet rather than a layer of positive charge at the surface of the specimen. A simple model of th… more
Date: April 15, 2003
Creator: Glaeser, Robert M. & Downing, Kenneth H.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Analytical Electron Microscopy Characterization of Uranium-Contaminated Soils from the Fernald Site, FY1993 Report

Description: A combination of optical microscopy, scanning electron microscopy with backscattered electron detection (SEM/BSE), and analytical electron microscopy (AEM) is being used to determine the nature of uranium in soils from the Fernald Environmental Management Project. The information gained from these studies is being used to develop and test remediation technologies. Investigations using SEM have shown that uranium is contained within particles that are typically 1 to 100 micrometers in diameter. … more
Date: October 1994
Creator: Buck, E. C.; Cunnane, J. C.; Brown, N. R. & Dietz, N. L.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Study of dislocations in copper by weak beam, stereo, and in situ straining TEM

Description: Conventional transmission electron microscopy (TEM) has been an invaluable tool for verifjhg and developing dislocation theories since the first direct observations of dislocations were made using a TEM in the 1950s. Several useful techniques and technological advancements have been made since, helping fbrther the advancement of dislocation knowledge. The present paper concerns two studies of dislocations in copper made by coupling several of these techniques, specifically weak beam, in situ st… more
Date: January 1, 2002
Creator: McCabe, R. J. (Rodney J.); Misra, A. (Amit) & Mitchell, T. E. (Terence E.)
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Partner: UNT Libraries Government Documents Department
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Scanning transmission x-ray microscopy of unaltered biological specimens

Description: A scanning transmission x-ray microscope at the National Synchrotron Light Source was used to image fresh, wet biological specimens at 32 Angstroms, with resolution better than 750 Angstroms. A gold Fresnel zone plate (outer zone width 500 Angstroms) was used to focus the undulator radiation, and the sample was scanned through the spot. Absorption data was recorded digitally as a gridded array. The major accomplishment of the experiment was the demonstration of the ability to image biological s… more
Date: May 1, 1987
Creator: Iskander, N.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Transmission Electron Microscopy Study of Nonpolar a-Plane GaNGrown by Pendeo-Epitaxy on (112_0) 4H-SiC

Description: Pendeo-epitaxy has been applied to nonpolar a-plane GaN layers in order to observe if such process will lead to defect reduction in comparison with direct growth on this plane. Uncoalesced and coalesced a-plane GaN layers with thicknesses 2{micro}m and 12{micro}m, respectively have been studied by conventional and high resolution electron microscopy. The following structural defects have been observed in pendeo-epitaxial layers: (1) basal stacking faults, (2) threading dislocations and (3) pris… more
Date: March 10, 2005
Creator: Zakharov, D. N.; Liliental-Weber, Z.; Wagner, B.; Reitmeier, Z. J.; Preble, E. A. & Davis, R. F.
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Partner: UNT Libraries Government Documents Department
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Quantitative Sub-Angstrom Imaging Through ADF STEM

Description: ORNL/CP-100163 Annular dark-field (ADF) imaging in a scanning transmission electron microscope (STEM) at atomic resolution provides an incoherent image that can be described as the convolution between the intensity of the illuminating STEM probe and an object function consisting of localised sources at the atomic-column positions. It has been shown that the resolution limit of the microscope limits the accuracy to which the object function can be reconstructed [1]. Here we demonstrate how a num… more
Date: August 31, 1998
Creator: Nellist, P.D. & Pennycook, S.J.
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Partner: UNT Libraries Government Documents Department
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The optimum Cs condition for high-resolution transmission electron microscopy

Description: With the advent of electron-optical systems able to generate negative spherical aberration (usually called ''Cs correctors''), it has now become feasible to zero-out objective lens Cs in the high-resolution transmission electron microscope. However, I show that - instead of tuning out spherical aberration completely - there is an optimum value for the residual Cs that maximizes information transfer to the best possible resolution and depends only on the information limit of the microscope.
Date: February 14, 2000
Creator: O'Keefe, Michael A.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Direct Observations of Defect Structures in Optoelectronic Materials by Z-Contrast STEM

Description: Optoelectronic semiconductor materials have wide and important technological applications. For example, wide gap nitride semiconductors have attracted significant attention recently due to their promising performance as short-wavelength light emitting diodes (LEDs) and blue lasers, while HgCdTe II-VI semiconductors are the most promising candidates for applications as infrared detectors, or large array x-ray or r-ray detectors. In this paper, two examples are given to show that high-resolution … more
Date: August 31, 1998
Creator: Beaumont, B.; Browning, N. D.; Chen, Y. P.; Faurie, J. P.; Gibart, P.; Nellist, P. D. et al.
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Partner: UNT Libraries Government Documents Department
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Local indium segregation and band structure in high efficiencygreen light emitting InGaN/GaN diodes

Description: GaN/InGaN light emitting diodes (LEDs) are commercialized for lighting applications because of the cost efficient way that they produce light of high brightness. Nevertheless, there is significant room for improving their external emission efficiency from typical values below 10 percent to more than 50 percent, which are obtainable by use of other materials systems that, however, do not cover the visible spectrum. In particular, green-light emitting diodes fall short in this respect, which is t… more
Date: November 23, 2004
Creator: Jinschek, Joerg R.; Erni, Rolf; Gardner, Nathan F.; Kim, AndrewY. & Kisielowski, Christian
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Z-contrast imaging and grain boundaries in semiconductors

Description: Interest in grain boundaries in semiconductors is linked to the application of polycrystalline semiconductors as photovoltaic and interconnect materials. In real devices such as solar cells and MOS structures as well as future devices such as flat-panel displays, the intergranular regions of the polycrystalline solid have a significant effect on the flow of electronic current. These grain boundary barriers exist because the chemical potential of the boundary atoms are shifted from the bulk valu… more
Date: March 1, 1996
Creator: Chisholm, M.F. & Pennycook, S.J.
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Partner: UNT Libraries Government Documents Department
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Structure of low-density nanoporous dielectrics revealed by low-vacuum electron microscopy and small-angle x-ray scattering

Description: We use low-vacuum scanning electron microscopy to image directly the ligament and pore size and shape distributions of representative aerogels over a wide range of length scales ({approx} 10{sup 0}-10{sup 5} nm). The images are used for unambiguous, real-space interpretation of small-angle scattering data for these complex nanoporous systems.
Date: June 5, 2006
Creator: Kucheyev, S O; Toth, M; Baumann, T F; Hamza, A V; Ilavsky, J; Knowles, W R et al.
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Partner: UNT Libraries Government Documents Department
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A CCD Camera with Electron Decelerator for Intermediate Voltage Electron Microscopy

Description: Electron microscopists are increasingly turning to Intermediate Voltage Electron Microscopes (IVEMs) operating at 300 - 400 kV for a wide range of studies. They are also increasingly taking advantage of slow-scan charge coupled device (CCD) cameras, which have become widely used on electron microscopes. Under some conditions CCDs provide an improvement in data quality over photographic film, as well as the many advantages of direct digital readout. However, CCD performance is seriously degraded… more
Date: March 17, 2008
Creator: Downing, Kenneth H; Downing, Kenneth H. & Mooney, Paul E.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Alpha-null defocus: An optimum defocus condition with relevance for focal-series reconstruction

Description: Two optimum defocus conditions are used in high-resolution transmission electron microscopy. Scherzer defocus produces an image of the specimen ''projected potential'' to the resolution of the microscope, and Lichte defocus minimizes dispersion. A third optimum defocus is best for focal-series reconstruction; alpha-null defocus maximizes transfer of high-frequency diffracted beam amplitudes into the microscope image. Beam transfer is confined by incident-beam convergence to a Gaussian ''packet'… more
Date: February 14, 2001
Creator: O'Keefe, Michael A.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Sub-Angstrom transmission electron microscopy at 300keV

Description: We have demonstrated sub-Angstrom TEM to a resolution of 0.78 Angstrom with the one-Angstrom microscope (OAM) project at the National Center for Electron Microscopy. The OAM combines a modified CM300FEG-UT with computer software able to generate sub-Angstrom images from experimental image series. We achieved sub-Angstrom resolution with the OAM by paying close attention to detail. We placed the TEM in a favorable environment. We reduced its three-fold astigmatism A2 from 2.46mm to 300 Angstrom … more
Date: February 14, 2001
Creator: O'Keefe, Michael A.; Nelson, E. Christian; Turner, John H. & Thust, Andreas
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Structural properties of free-standing 50 mm diameter GaN waferswith (101_0) orientation grown on LiAlO2

Description: (10{und 1}0) GaN wafers grown on (100) face of {gamma}-LiAlO{sub 2} were studied using transmission electron microscopy. Despite good lattice matching in this heteroepitaxial system, high densities of planar structural defects in the form of stacking faults on the basal plane and networks of boundaries located on prism planes inclined to the layer/substrate interface were present in these GaN layers. In addition, significant numbers of threading dislocations were observed. High-resolution elect… more
Date: September 27, 2005
Creator: Jasinski, Jacek; Liliental-Weber, Zuzanna; Maruska, Herbert-Paul; Chai, Bruce H.; Hill, David W.; Chou, Mitch M.C. et al.
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Partner: UNT Libraries Government Documents Department
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Direct sublattice imaging of interface dislocation structures in CdTe/GaAs(001)

Description: This paper presents directly interpretable atomic resolution images of dislocation structures at interfaces in CdTe/GaAs(001) systems. This is achieved using the technique of Z-contrast imaging in a 300 kV scanning transmission electron microscope in conjunction with maximum entropy image analysis. In addition to being used to further the understanding of the relation between growth conditions and exhibited properties, the data presented provides direct information on the atomic arrangements at… more
Date: January 1995
Creator: McGibbon, A.J.; Pennycook, S.J.; Angelo, J.E. & Mills, M.J.
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Partner: UNT Libraries Government Documents Department
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Three-Dimensional Aberration-Corrected Scanning Transmission Electron Microscopy for Biology

Description: Recent instrumental developments have enabled greatly improved resolution of scanning transmission electron microscopes (STEM) through aberration correction. An additional and previously unanticipated advantage of aberration correction is the greatly improved depth sensitivity that has led to the reconstruction of a three-dimensional (3D) image from a focal series. In this chapter the potential of aberration-corrected 3D STEM to provide major improvements in the imaging capabilities for biologi… more
Date: January 1, 2007
Creator: De Jonge, Niels; Sougrat, Rachid; Pennycook, Stephen J; Peckys, Diana B & Lupini, Andrew R
Item Type: Refine your search to only Book
Partner: UNT Libraries Government Documents Department
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