Clustering for scanning transmission electron diffraction data

There is significant current interest in understanding the structure of aperiodic solids, such as originally crystalline material amorphized by ion implantation, impact or application of massive pressures, or deposited amorphous thin films, which occupy small volumes. Radially-averaged real-space distribution functions can be derived from diffraction data, the best of which come from thermal neutron diffraction, which inconveniently requires large volumes. Neutron data are collectable in reciprocal space out to q ≡ 2sin(Θ/2)/λ = 70 nm-1, where Θ is the scattering angle and λ the wavelength, or about twice as far as for X-rays, which also require large diffracting volumes. Electron diffraction is the only recourse for very small volumes because of the much stronger interaction of the electron, but spectra must be energy filtered to remove the large inelastic scattering component. Recently, it has been shown that useful electron diffraction data can be collected conveniently to at least q = 16 nm-1 in the VG HB5 dedicated 100-kV field-emission STEM. This contribution details our experiences with improved collection in the VG HB603 instrument operating at 250 kV.

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On the Determination of Partial RDFs for Amorphous Materials

MRS Proceedings ◽

10.1557/proc-321-39 ◽

1993 ◽

Vol 321 ◽

Cited By ~ 1

Author(s):

L. C. Qin ◽

L. W. Hobbs

Keyword(s):

Electron Diffraction ◽

Diffraction Data ◽

Amorphous Materials ◽

Vitreous Silica ◽

Scanning Transmission Electron Microscope ◽

Distribution Functions ◽

Electron Diffraction Data ◽

X Ray ◽

Transmission Electron ◽

Scanning Transmission

ABSTRACTRadial distribution functions (RDFs) for vitreous silica (V-SiO2) have been obtained from energy-filtered electron diffraction data obtained in the HB5 scanning transmission electron Microscope. Results have been compared with those obtained from high-resolution neutron diffraction experiments, and are in good agreement within experimental errors. It was found to be impractical to obtain partial RDFs for this material from combined neutron, X-ray and electron diffraction data, because the similarities in characteristics of X-ray and electron scattering cause indeter-Minacies. A criterion equation has been given to determine feasibility.

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Structure of the in on SI(111)4X1 Surface Determined by Applying Direct Phasing Methods to Transmission Electron Diffraction Data

Microscopy and Microanalysis ◽

10.1017/s1431927600012095 ◽

1997 ◽

Vol 3 (S2) ◽

pp. 1041-1042

Author(s):

C. Collazo-Davila ◽

L. D. Marks ◽

K. Nishii ◽

Y. Tanishiro

Keyword(s):

Electron Diffraction ◽

Diffraction Data ◽

Direct Methods ◽

Surface Structures ◽

Electron Diffraction Data ◽

Imaging Plate ◽

Data Sets ◽

Interface Formation ◽

Transmission Electron Diffraction ◽

Transmission Electron

Direct methods were applied to transmission electron diffraction data to solve the previously unknown In on Si(111)4x1 surface structure. The structure consists of zig-zag chains of In atoms separated by regions of silicon including dimer chains (Fig 1.). The 4x1 structure is one of several stable surface structures formed with increasing In coverages on the Si(111) surface. The √3x√3 structure consists of 1/3 of a monolayer of In, the √31x√31 occurs at a slightly higher coverage and the 4x1 structure appears before the formation of In islands on the surface . While the √3x√3 surface has been extensively studied, relatively little is known about the √31x√31 and 4x1 structures. Knowledge of the atomic positions in the 4x1 structure is an important step in understanding metal/semiconductor epitaxy and interface formation.Two data sets were used in this study -- the first recorded on film and reduced in Tokyo, the second recorded on Imaging Plate in Tokyo and reduced at Northwestern. Twenty-seven independent intensities were measured.

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ATOMIC STRUCTURE OF THE In ON Si(111)(4 × 1) SURFACE

Surface Review and Letters ◽

10.1142/s0218625x97000110 ◽

1997 ◽

Vol 04 (01) ◽

pp. 65-70 ◽

Cited By ~ 38

Author(s):

C. COLLAZO-DAVILA ◽

L. D. MARKS ◽

K. NISHII ◽

Y. TANISHIRO

Keyword(s):

Electron Diffraction ◽

Diffraction Data ◽

Atomic Structure ◽

Direct Methods ◽

Electron Diffraction Data ◽

Zigzag Chain ◽

Transmission Electron Diffraction ◽

Transmission Electron

The atomic structure of the In on Si (111)(4×1) surface has been determined using direct methods applied to transmission electron diffraction data. It consists of a zigzag chain of In atoms and a region of silicon including a dimer chain. The structure is sufficiently similar to recent models of the Au on Si (111)(5×2) and metal on Si (111)(3×1) structures, that some preliminary generalizations on the linear n×1 and n×2 Si(111) reconstructions can be made.

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Structural Coherence and Magnetic Coupling in Fe/Si

MRS Proceedings ◽

10.1557/proc-384-183 ◽

1995 ◽

Vol 384 ◽

Author(s):

C.L. Foiles ◽

M.R. Franklin ◽

R. Loloee

Keyword(s):

Electron Diffraction ◽

Saturation Magnetization ◽

Diffraction Data ◽

Direct Evidence ◽

Magnetic Coupling ◽

Electron Diffraction Data ◽

Transmission Electron Diffraction ◽

Transmission Electron ◽

Structural Coherence ◽

Magnetization Behavior

ABSTRACTA number of studies have inferred the presence of an Fe-silicide in Fe/Si multilayers. Our transmission electron diffraction data provide direct evidence for the presence of an Fe-silicide. Despite similarities in structural coherence and saturation magnetization behavior for Fe/Si and Fe/{FeSi}, direct evidence for Fe-silicide only occurs for the Fe/{FeSi} multilayers.

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Rocking Beam Microarea Diffraction Applied to Metallic thin Films

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100091962 ◽

1976 ◽

Vol 34 ◽

pp. 396-397

Author(s):

R. H. Geiss

Keyword(s):

Thin Films ◽

Electron Diffraction ◽

Small Area ◽

Objective Lens ◽

Electron Optics ◽

Metallic Thin Films ◽

Transmission Electron Diffraction ◽

Transmission Electron ◽

Sample Height ◽

Scanning Transmission

The theory and practical limitations of micro area scanning transmission electron diffraction (MASTED) will be presented. It has been demonstrated that MASTED patterns of metallic thin films from areas as small as 30 Åin diameter may be obtained with the standard STEM unit available for the Philips 301 TEM. The key to the successful application of MASTED to very small area diffraction is the proper use of the electron optics of the STEM unit. First the objective lens current must be adjusted such that the image of the C2 aperture is quasi-stationary under the action of the rocking beam (obtained with 40-80-160 SEM settings of the P301). Second, the sample must be elevated to coincide with the C2 aperture image and its image also be quasi-stationary. This sample height adjustment must be entirely mechanical after the objective lens current has been fixed in the first step.

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Models of Magnesium Oxide (111) Surface Reconstructions Obtained from Direct Phasing of Transmission Electron Diffraction Data

Microscopy and Microanalysis ◽

10.1017/s1431927600012083 ◽

1997 ◽

Vol 3 (S2) ◽

pp. 1039-1040

Author(s):

R. Plass ◽

K. Egan ◽

C. Collazo-Davila ◽

D. Grozea ◽

E. Landree ◽

...

Keyword(s):

Electron Microscopy ◽

Electron Diffraction ◽

Electron Diffraction Data ◽

Vacuum Furnace ◽

Transmission Electron Diffraction ◽

Transmission Electron ◽

Surface Reconstructions ◽

Reflection Electron Microscopy ◽

Plane Disk ◽

Flowing Oxygen

It has long been thought that (111) surfaces of rock salt oxides microfacet to neutral surfaces upon annealing because of the very large energies involved in bulk terminating a layer of like ions. However in a recent reflection electron microscopy (REM) study Gajdardziska-Josifovska et al. found that MgO(lll) surfaces annealed in flowing oxygen furnaces at 1500°C not only did not microfacet, but displayed a √3×√3R30° surface periodicity that was stable in air. To determine the structure of this unusually stable surface MgO (111) transmission electron microscopy (TEM) samples were annealed in a vacuum furnace in the present study and their transmission electron diffraction (TED) patterns were analyzed with direct phasing methods.The TEM samples were prepared by orienting a MgO single crystal and sawing lmm wafers along a (111) plane. Disk samples were then ultrasonically drilled, dimpled, mechanically polished and/or hot nitric acid etched, and milled with 5 KeV Ar+ ions.

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STRUCTURE DETERMINATION OF THE Ge(111)-(3×1)Ag SURFACE RECONSTRUCTION

Surface Review and Letters ◽

10.1142/s0218625x99001153 ◽

1999 ◽

Vol 06 (06) ◽

pp. 1061-1065 ◽

Cited By ~ 6

Author(s):

D. GROZEA ◽

E. BENGU ◽

C. COLLAZO-DAVILA ◽

L. D. MARKS

Keyword(s):

Electron Diffraction ◽

Surface Reconstruction ◽

Diffraction Data ◽

Structure Determination ◽

Heavy Atom ◽

Direct Methods ◽

Electron Diffraction Data ◽

Transmission Electron ◽

First Time

For the first time, during the investigation of the Ag submonolayer on the Ge(111) system, large, independent domains of the Ge (111)-(3×1) Ag phase were imaged and investigated. Previous studies have reported it only as small insets between Ge (111)-(4×4) Ag and Ge (111)- c (2×8) domains. The transmission electron diffraction data were analyzed using a Direct Methods approach and "heavy-atom holography," with the result of an atomic model of the structure similar to that of Ge (111)-(3×1) Ag .

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