The Direct Observation of Atomic Surface Structure and Inclined Planar Defects in Au(111) Films

1981 ◽  
Vol 10 ◽  
Author(s):  
William Krakow
Keyword(s):  
Single Atom ◽  
Bottom Surface ◽  
Stacking Sequence ◽  
Planar Defects ◽  
Resolution Electron ◽  
Atomic Surface ◽  
High Resolution Electron Microscope ◽  
Diffraction Effects ◽  
First Time ◽  
Image Simulations

With a high resolution electron microscope it is possible to image directly the atomic surface lattice of vapor-deposited Au(111) films. The contrast of the surface atoms can be either black or white relative to the background which is characteristic of close-packed planes of atoms in the stacking sequence ABCABC.... An analysis of these images was performed using multislice dynamical diffraction computations of 256 × 256 = 65 536 reciprocal space points and subsequent image simulations. The effects of top and bottom surface roughness, different termination layers and the contrast compared with single-atom imaging are considered.The identification of atomic structure detail at incoherent double-position boundaries in these (111) films was also achieved. Surface layer terminations, variations in the choice of every third matching plane and the possibility that twinning planes produce boundaries with jogs were investigated. Multislice computer programs were designed to calculate the diffraction effects from these inclined boundaries using two-dimensional fast Fourier transform and shift techniques of the projected potential. This is the first time that inclined planar defects have been analyzed in this manner.

Interpretation of the Atomic Surface Structure of Ag2O on (111) Au thin films

1983 ◽  
Vol 31 ◽  
Author(s):  
William Krakow
Keyword(s):  
Surface Structure ◽  
Image Features ◽  
Electron Microscope Investigation ◽  
Resolution Electron ◽  
Atomic Surface ◽  
High Resolution Electron Microscope ◽  
Au Thin Films ◽  
Diffraction Patterns ◽  
Digital Frame ◽  
Image Simulations

ABSTRACTA high resolution electron microscope investigation of the residual oxidized silver of a few monolayers thickness on the surface of (111) Au films has shown that a reconstructed (2×1) surface structure occurs for (110) oriented Ag2O and can be observed at atomic resolution levels. Image enhancement via a digital frame store processor has revealed improved images which have then been compared to computer simulated diffraction patterns and images of the Ag2O surface. Several iterations of surface structure models and image simulations reveal that the (2×1) reconstruction is consistent with a missing row model. The atomic arrangements of these rows often undergo a translation along the direction of the row to produce cusp like image features. It has also been possible to observe the effect of contraction of the underlying layer which can produce diagonal contrast lines in the images. These features often vary rapidly over lateral distances of a few tens of angstroms and give an indication of the surface topography and the degree ordering of the surface.

Dynamic TEM Observation on Oxide Glass Materials

1990 ◽  
Vol 183 ◽  
Author(s):  
Sumio Iijima
Keyword(s):  
Electron Beam Irradiation ◽  
Amorphous Film ◽  
Oxide Glass ◽  
Model Structure ◽  
Resolution Electron ◽  
Atom Migration ◽  
Intense Electron Beam ◽  
High Resolution Electron Microscope ◽  
Intense Electron ◽  
Image Simulations

AbstractIntensity fluctuation in high resolution electron microscope (HREM) images of amorphous Tl-Ba-Ca-Cu-O oxide films is observed. The fluctuation with a frequency of few tens of Hertz and an amplitude of about 0.3nm, occurs under an intense electron beam irradiation. It is shown experimentally that atom migration in the films is responsible for the fluctuations. The result is also supported by computer image simulations on a model structure for amorphous film.

Crystalline silica nanowires

2004 ◽  
Vol 19 (8) ◽  
pp. 2216-2220 ◽  
Author(s):  
F.L. Deepak ◽  
Gautam Gundiah ◽  
Md. Motin Seikh ◽  
A. Govindaraj ◽  
C.N.R. Rao
Keyword(s):  
Fumed Silica ◽  
X Ray Diffraction ◽  
X Ray ◽  
Starting Mixture ◽  
Resolution Electron ◽  
Silica Nanowires ◽  
Microscope Images ◽  
High Resolution Electron Microscope ◽  
Silica Ratio ◽  
First Time

α-Cristobalite nanowires of 50–100 nm diameter with lengths of several microns have been synthesized for the first time by the solid-state reaction of fumed silica and activated charcoal. The nanowires have been characterized by x-ray diffraction, electron microscopy, photoluminescence, and Raman scattering. The nanowires are single crystalline as revealed by high-resolution electron microscope images. The crystalline nanowires are clad by an amorphous silica sheath when the carbon to fumed silica ratio in the starting mixture is small. Use of hydrogen along with Ar helps to eliminate the amorphous sheath.

Interfacial structure and interfacial reactions at the MgO/Al2O3 interface

1991 ◽  
Vol 49 ◽  
pp. 696-697
Author(s):  
D. X. Li ◽  
P. Pirouz ◽  
A. H. Heuer ◽  
S. Yadavalli ◽  
C. P. Flynn
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Molecular Beam ◽  
Interfacial Structure ◽  
Cross Sectional ◽  
Resolution Electron ◽  
High Resolution Electron Microscope ◽  
Electron Microscope Image ◽  
Image Simulations ◽  
Standard Techniques

MgO films were deposited on the (sample A), (0001)Al2O3 (sample B), and the (sample C) planes of sapphire by Molecular Beam Epitaxy (MBE). Cross-sectional UREM specimens were prepared using standard techniques and examined in a top-entry JEOL 4000FX high resolution electron microscope. Image simulations were performed using the SHRLI programs developed by O'Keefe.

Interfacial Structures in the Nb/MgO/Nb/Al2O3 Superlattice

1991 ◽  
Vol 49 ◽  
pp. 960-961
Author(s):  
D. X. Li ◽  
P. Pirouz ◽  
A. H. Heuer ◽  
S. Yadavalli ◽  
C. P. Flynn
Keyword(s):  
Ion Beam ◽  
Mechanical Grinding ◽  
Cross Sectional ◽  
Mbe Growth ◽  
Resolution Electron ◽  
Interfacial Structures ◽  
High Resolution Electron Microscope ◽  
Point To Point ◽  
Image Simulations ◽  
Standard Techniques

Nb/MgO/Nb/Al2O3 superlattices were prepared by MBE growth of Nb and MgO films on a (012)Al2O3 sapphire substrate. Cross sectional HREM specimens were prepared using standard techniques involving mechanical grinding to a thickness of 0.13 mm, dimpling to a thickness of 20 μm and ion beam milling at 6 kV. The samples were subsequently examined in a top-entry JEOL 4000EX high resolution electron microscope with a point-to-point resolution of ∼0.19 nm. Image simulations were performed using the SHRLI programs developed by O'Keefe.

High Resolution Study of CoSi2/Si (111) Interfaces

1990 ◽  
Vol 183 ◽  
Author(s):  
A. Catana ◽  
Ping Lu ◽  
David J. Smith
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Cross Section ◽  
Atomic Structure ◽  
Interface Bonding ◽  
Resolution Electron ◽  
High Resolution Electron Microscope ◽  
Image Simulations ◽  
Resolution Study

AbstractThe atomic structure of A- and B-type CoSi2/Si (111) interfaces has been investigated by observations of samples in cross-section using a 400 kV high-resolution electron microscope. The samples were prepared by UHV e–beam evaporation of Co layers followed by annealing at temperatures between 300°C and 500°C. Based upon image simulations for various interface bonding models we have found evidence for 7–fold Co coordination at the A–type CoSi2/Si interfaces and for 7– and 8–fold coordination at the B-type interfaces.

Study of TE Puke Halloysite by a High Resolution Electron Microscope

1973 ◽  
Vol 31 ◽  
pp. 200-201
Author(s):  
T. R. McKee ◽  
J. B. Dixon ◽  
U. G. Whitehouse ◽  
D. F. Harling
Keyword(s):  
Basal Spacing ◽  
X Ray Diffraction ◽  
Lattice Imaging ◽  
Direct Examination ◽  
Electron Microscopic ◽  
Electron Diffraction Investigation ◽  
X Ray ◽  
Resolution Electron ◽  
High Resolution Electron Microscope ◽  
Diffraction Effects

Clay minerals normally exhibit platy morphology with basal spacings parallel to the surface of an aggregate and registering characteristic x-ray diffraction effects. For the same reason the majority of the electron microscopic lattice imaging has been accomplished using embedded and ultrathin sectioned clays, allowing the basal spacing to be correctly oriented with respect to the electron beam. Yada has observed lattice spacings in chrysotile (a tubular mineral) by direct examination.Halloysite is a type of kaolin clay mineral that usually exhibits curved layers as tubes and spheroids which reduces the x-ray diffraction intensities from preferred orientation mounts while exposing the basal spacing for electron diffraction investigation and lattice imaging.

Electron microscopy and diffraction studies of polyimides

1983 ◽  
Vol 41 ◽  
pp. 28-29
Author(s):  
O.C. de Hodgins ◽  
K. R. Lawless ◽  
R. Anderson
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Structural Features ◽  
Inert Atmosphere ◽  
Polyimide Films ◽  
Resolution Electron ◽  
The Matrix ◽  
High Resolution Electron Microscope ◽  
Diffraction Patterns ◽  
Polymeric Samples

Commercial polyimide films have shown to be homogeneous on a scale of 5 to 200 nm. The observation of Skybond (SKB) 705 and PI5878 was carried out by using a Philips 400, 120 KeV STEM. The objective was to elucidate the structural features of the polymeric samples. The specimens were spun and cured at stepped temperatures in an inert atmosphere and cooled slowly for eight hours. TEM micrographs showed heterogeneities (or nodular structures) generally on a scale of 100 nm for PI5878 and approximately 40 nm for SKB 705, present in large volume fractions of both specimens. See Figures 1 and 2. It is possible that the nodulus observed may be associated with surface effects and the structure of the polymers be regarded as random amorphous arrays. Diffraction patterns of the matrix and the nodular areas showed different amorphous ring patterns in both materials. The specimens were viewed in both bright and dark fields using a high resolution electron microscope which provided magnifications of 100,000X or more on the photographic plates if desired.

An Analysis of Dissociation of Molecules in a High Resolution Electron Microscope

1973 ◽  
Vol 31 ◽  
pp. 486-487
Author(s):  
Mihir Parikh
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Cross Sections ◽  
Resolving Power ◽  
Peak Intensity ◽  
Molecular Film ◽  
Resolution Electron ◽  
Dissociation Cross Section ◽  
High Resolution Electron Microscope ◽  
The Stability

It is well known that the resolution of bio-molecules in a high resolution electron microscope depends not just on the physical resolving power of the instrument, but also on the stability of these molecules under the electron beam. Experimentally, the damage to the bio-molecules is commo ly monitored by the decrease in the intensity of the diffraction pattern, or more quantitatively by the decrease in the peaks of an energy loss spectrum. In the latter case the exposure, EC, to decrease the peak intensity from IO to I’O can be related to the molecular dissociation cross-section, σD, by EC = ℓn(IO /I’O) /ℓD. Qu ntitative data on damage cross-sections are just being reported, However, the microscopist needs to know the explicit dependence of damage on: (1) the molecular properties, (2) the density and characteristics of the molecular film and that of the support film, if any, (3) the temperature of the molecular film and (4) certain characteristics of the electron microscope used

Atomic-level imaging of the surface structure of Ag2O

1984 ◽  
Vol 42 ◽  
pp. 656-657
Author(s):  
William Krakow
Keyword(s):  
High Vacuum ◽  
Atomic Level ◽  
Ultra High Vacuum ◽  
Research Groups ◽  
Resolution Electron ◽  
Surface Reconstructions ◽  
Order Of Magnitude ◽  
High Resolution Electron Microscope ◽  
Saturated Structure ◽  
Transmission And Reflection

In recent years electron microscopy has been used to image surfaces in both the transmission and reflection modes by many research groups. Some of this work has been performed under ultra high vacuum conditions (UHV) and apparent surface reconstructions observed. The level of resolution generally has been at least an order of magnitude worse than is necessary to visualize atoms directly and therefore the detailed atomic rearrangements of the surface are not known. The present author has achieved atomic level resolution under normal vacuum conditions of various Au surfaces. Unfortunately these samples were exposed to atmosphere and could not be cleaned in a standard high resolution electron microscope. The result obtained surfaces which were impurity stabilized and reveal the bulk lattice (1x1) type surface structures also encountered by other surface physics techniques under impure or overlayer contaminant conditions. It was therefore decided to study a system where exposure to air was unimportant by using a oxygen saturated structure, Ag2O, and seeking to find surface reconstructions, which will now be described.

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