The Observation of Atomic Surface Structure from Au Thin Films

1981 ◽  
Vol 39 ◽  
pp. 200-203
Author(s):  
William Krakow ◽  
G. Trafas
Keyword(s):  
Surface Structure ◽  
Incident Beam ◽  
Dark Field ◽  
Transmission Electron ◽  
Unit Cells ◽  
Crystalline Films ◽  
Microscope Imaging ◽  
Lattice Unit ◽  
Atomic Surface ◽  
Au Thin Films

The direct imaging of the surface structure of thin crystalline films in the conventional transmission electron microscope (CTEM) requires resolution of a few angstroms both laterally and perpendicular to the atomic surface layers. Although the lateral resolution was not achieved, dark-field images of the forbidden reflections from (111) Au films could be employed to image lateral areas ∼500Å diameter. The first atomic level resolution pictures of the Au surface of (001) films were reported by Krakow and Ast. Here optical diffractograms revealed the presence of the forbidden surface reflections due to partially filled bulk lattice unit cells corresponding to a surface lattice periodicity of ∼2.86Å. Subsequently, improved electron micrographs were obtained at incident beam energies of lOOkV and at ImeV where in the latter case the microscope resolution was better than 2Å3. Several diffraction experiments were also performed to understand the nature of the surface structure of (001)Au. In this study models of a “single” (001)Au surface were constructed and computations performed to demonstrate the types of images attainable at different resolution levels and under different microscope imaging conditions.

Direct observation ofB-site cation displacements in Pb-based complex perovskite relaxor oxides

2010 ◽  
Vol 44 (1) ◽  
pp. 111-121 ◽  
Author(s):  
K. Z. Baba-Kishi
Keyword(s):  
Long Range ◽  
Scanning Transmission Electron Microscope ◽  
Dark Field ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Unit Cells ◽  
Annular Dark Field ◽  
Pb Ions ◽  
Diffraction Patterns ◽  
Spatial Displacements

Electron diffraction patterns recorded using a scanning transmission electron microscope (STEM) from PbMg1/3Nb2/3O3(PMN) crystallites and PbZn1/3Nb2/3O3(PZN) crystals show weak and systematic continuous diffuse streaking along the 〈110〉 directions. Detailed high-angle annular dark-field (HAADF) images recordedviaan aberration-corrected STEM show that theB-site cations in PMN and PZN undergo correlated and long-range displacements towards the Pb2+ions on the (110) planes. The planarB-site displacement measured from the centres of the octahedra is about 0.3–0.5 Å in PMN and about 0.20–0.4 Å in PZN. In the HAADF images of the PMN crystallites and PZN crystals studied, there is insufficient evidence for systematic long-range planar displacements of the Pb2+ions. The observed Pb2+ion displacements in PMN and PZN appear randomly distributed, mostly displaced along 〈110〉 towards theB-site columns. There is also evidence of possible stress-related distortion in certain unit cells of PMN. In the relaxors studied, two distinct types of displacements were observed: one is the long-range planarB-site spatial displacement on the (110) planes, correlated with the Pb2+ions, possibly resulting in the observed diffuse streaking; the other is short-range Pb2+ion displacement on the (110) planes. The observed displacement status indicates a mutual attraction between the Pb ions and theB-site cations in which theBsites undergo the largest spatial displacements towards the Pb ions along 〈110〉.

scholarly journals Novel kind of decagonal ordering in Al74Cr15Fe11

2020 ◽  
Author(s):  
Haikun Ma ◽  
Zhanbing He ◽  
Hua Li ◽  
Tiantian Zhang ◽  
Shuang Zhang ◽  
...  
Keyword(s):  
Scanning Transmission Electron Microscopy ◽  
Dark Field ◽  
High Angle ◽  
Decagonal Quasicrystal ◽  
Transmission Electron ◽  
Aperiodic Order ◽  
Scanning Transmission ◽  
Unit Cells ◽  
Annular Dark Field ◽  
The Common

Abstract A high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) study of the intermetallic compound Al74Cr15Fe11 reveals a novel kind of aperiodic order. In contrast to the common quasi-unit-cells based on Gummelt decagons, the present structure is related to a covering formed by Andritz decagons, which can also be described by a Hexagon-Bowtie (HB) tiling. This is the first observation of a decagonal quasicrystal with a structure significantly differing from the ones known so far.

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.

Dark-Field and Marginal Imaging with a Thin-Annular Detector in STEM

1996 ◽  
Vol 2 (1) ◽  
pp. 9-19
Author(s):  
R.-J. Liu ◽  
J.M. Cowley
Keyword(s):  
Diffraction Pattern ◽  
Amorphous Materials ◽  
Incident Beam ◽  
Scanning Transmission Electron Microscope ◽  
Dark Field ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Imaging Mode ◽  
Annular Detector ◽  
Diffraction Patterns

The use of a thin annular detector in a scanning transmission electron microscope is shown, theoretically and experimentally, to allow several imaging modes that may be of value for the study of thin specimens. The diffraction pattern on the detector plane may be expanded or contracted by means of post-specimen lenses to vary the collection angle of the thin annular detector to form dark- or bright-field images. Dark-field images obtained from annuli of various radii in the diffraction pattern can selectively reveal different components of the sample, as illustrated in the case of a sample containing platinum crystallites, amorphous carbon, and carbon nanotubes. Amorphous materials of different composition can be distinguished by selecting the main maxima in their diffraction patterns. If the central beam is enlarged so that it just fills the inner aperture of the detector, the “marginal” imaging mode so achieved gives an image contrast that is proportional to the square of the differential of the projected potential distribution. Any deflection of the incident beam spot due to a change of the projected potential gives bright contrast in the image.

scholarly journals Novel kind of decagonal ordering in Al74Cr15Fe11

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Haikun Ma ◽  
Zhanbing He ◽  
Hua Li ◽  
Tiantian Zhang ◽  
Shuang Zhang ◽  
...  
Keyword(s):  
Microscopy Study ◽  
Dark Field ◽  
Electron Microscopy Study ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Unit Cells ◽  
Annular Dark Field ◽  
Quasiperiodic Structure ◽  
The Common ◽  
Bow Tie

AbstractA high-angle annular dark field scanning transmission electron microscopy study of the intermetallic compound Al74Cr15Fe11 reveals a quasiperiodic structure significantly differing from the ones known so far. In contrast to the common quasi-unit-cells based on Gummelt decagons, the present structure is related to a covering formed by Lück decagons, which can also be described by a Hexagon-Bow-Tie tiling.

Surface Structure of the Spores of Glugea Weissenbergi

1969 ◽  
Vol 27 ◽  
pp. 238-239
Author(s):  
Sanford H. Vernick ◽  
Anastasios Tousimis ◽  
Victor Sprague
Keyword(s):  
Electron Microscope ◽  
Surface Structure ◽  
Transmission Electron Microscope ◽  
Mature Spore ◽  
Spore Surface ◽  
Sectioned Material ◽  
Transmission Electron ◽  
Surface Detail

Recent electron microscope studies have greatly expanded our knowledge of the structure of the Microsporida, particularly of the developing and mature spore. Since these studies involved mainly sectioned material, they have revealed much internal detail of the spores but relatively little surface detail. This report concerns observations on the spore surface by means of the transmission electron microscope.

Resolution Attainable With the Present Day STEM

1973 ◽  
Vol 31 ◽  
pp. 230-231 ◽  
Author(s):  
J. S. Wall ◽  
J. P. Langmore ◽  
H. Isaacson ◽  
A. V. Crewe
Keyword(s):  
Spherical Aberration ◽  
Focal Length ◽  
Incident Beam ◽  
Scanning Transmission Electron Microscope ◽  
Aperture Size ◽  
Magnetic Lens ◽  
Peak Intensity ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Half Angle

The scanning transmission electron microscope (STEM) constructed by the authors employs a field emission gun and a 1.15 mm focal length magnetic lens to produce a probe on the specimen. The aperture size is chosen to allow one wavelength of spherical aberration at the edge of the objective aperture. Under these conditions the profile of the focused spot is expected to be similar to an Airy intensity distribution with the first zero at the same point but with a peak intensity 80 per cent of that which would be obtained If the lens had no aberration. This condition is attained when the half angle that the incident beam subtends at the specimen, 𝛂 = (4𝛌/Cs)¼

Enhancement of Contrast in the CEM and STEM Using Bumpy Specimens and Employing the “Dappled Field” Mode of Operation

1974 ◽  
Vol 32 ◽  
pp. 552-553 ◽  
Author(s):  
L. Gandolfi ◽  
J. Reiffel
Keyword(s):  
Operating Mode ◽  
Scanning Transmission Electron Microscope ◽  
Dark Field ◽  
Specimen Preparation ◽  
Field Mode ◽  
Preparation Methods ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Mode Of Operation ◽  
Scanning Transmission

Calculations have been performed on the contrast obtainable, using the Scanning Transmission Electron Microscope, in the observation of thick specimens. Recent research indicates a revival of an earlier interest in the observation of thin specimens with the view of comparing the attainable contrast using both types of specimens.Potential for biological applications of scanning transmission electron microscopy has led to a proliferation of the literature concerning specimen preparation methods and the controversy over “to stain or not to stain” in combination with the use of the dark field operating mode and the same choice of technique using bright field mode of operation has not yet been resolved.

An Electron Microscope Study of Interdiffusion and Compound Formation in Ta-Au Thin Films

1973 ◽  
Vol 31 ◽  
pp. 32-33 ◽  
Author(s):  
T. C. Tisone ◽  
S. Lau
Keyword(s):  
Electron Microscope ◽  
Electron Microscope Study ◽  
Thermally Grown Oxide ◽  
Ion Milling ◽  
Compound Formation ◽  
Technology Application ◽  
Transmission Electron ◽  
Before And After ◽  
Au Thin Films

In a study of the properties of a Ta-Au metallization system for thin film technology application, the interdiffusion between Ta(bcc)-Au, βTa-Au and Ta2M-Au films was studied. Considered here is a discussion of the use of the transmission electron microscope(TEM) in the identification of phases formed and characterization of the film microstructures before and after annealing.The films were deposited by sputtering onto silicon wafers with 5000 Å of thermally grown oxide. The film thicknesses were 2000 Å of Ta and 2000 Å of Au. Samples for TEM observation were prepared by ultrasonically cutting 3mm disks from the wafers. The disks were first chemically etched from the silicon side using a HNO3 :HF(19:5) solution followed by ion milling to perforation of the Au side.

A General Method for Spectrometer Design in the Scoff Approximation

1976 ◽  
Vol 34 ◽  
pp. 538-539
Author(s):  
J. R. Fields
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Energy Analysis ◽  
Incident Beam ◽  
Scanning Transmission Electron Microscope ◽  
Chemical Identification ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
General Method

The energy analysis of electrons scattered by a specimen in a scanning transmission electron microscope can improve contrast as well as aid in chemical identification. In so far as energy analysis is useful, one would like to be able to design a spectrometer which is tailored to his particular needs. In our own case, we require a spectrometer which will accept a parallel incident beam and which will focus the electrons in both the median and perpendicular planes. In addition, since we intend to follow the spectrometer by a detector array rather than a single energy selecting slit, we need as great a dispersion as possible. Therefore, we would like to follow our spectrometer by a magnifying lens. Consequently, the line along which electrons of varying energy are dispersed must be normal to the direction of the central ray at the spectrometer exit.

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