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

1997 ◽  
Vol 04 (01) ◽  
pp. 65-70 ◽  
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.

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

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.

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

1999 ◽  
Vol 06 (06) ◽  
pp. 1061-1065 ◽  
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 .

Structural Coherence and Magnetic Coupling in Fe/Si

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.

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

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.

Energy-filtered electron diffraction from amorphized solids in the dedicated scanning transmission electron microscope (STEM)¶

1996 ◽  
Vol 54 ◽  
pp. 702-703
Author(s):  
A. N. Sreeram ◽  
L.-C. Qin ◽  
A. J. Garratt-Reed ◽  
L. W. Hobbs
Keyword(s):  
Electron Diffraction ◽  
Diffraction Data ◽  
Scanning Transmission Electron Microscope ◽  
Real Space ◽  
Distribution Functions ◽  
Space Distribution ◽  
Electron Diffraction Data ◽  
X Rays ◽  
Transmission Electron ◽  
Scanning Transmission

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.

scholarly journals UsingFOCUSto solve zeolite structures from three-dimensional electron diffraction data

2013 ◽  
Vol 46 (4) ◽  
pp. 1017-1023 ◽  
Author(s):  
Stef Smeets ◽  
Lynne B. McCusker ◽  
Christian Baerlocher ◽  
Enrico Mugnaioli ◽  
Ute Kolb
Keyword(s):  
Electron Diffraction ◽  
Diffraction Data ◽  
Three Dimensional ◽  
Direct Methods ◽  
Electron Diffraction Data ◽  
Chemical Information ◽  
Data Sets ◽  
Dimensional Electron ◽  
Specific Chemical ◽  
Structure Solution

The programFOCUS[Grosse-Kunstleve, McCusker & Baerlocher (1997).J. Appl. Cryst.30, 985–995] was originally developed to solve zeolite structures from X-ray powder diffraction data. It uses zeolite-specific chemical information (three-dimensional 4-connected framework structure with known bond distances and angles) to supplement the diffraction data. In this way, it is possible to compensate, at least in part, for the ambiguity of the reflection intensities resulting from reflection overlap, and the program has proven to be quite successful. Recently, advances in electron microscopy have led to the development of automated diffraction tomography (ADT) and rotation electron diffraction (RED) techniques for collecting three-dimensional electron diffraction data on very small crystallites. Reasoning that such data are also less than ideal (dynamical scattering, low completeness, beam damage) and that this can lead to failure of structure solution by conventional direct methods for very complex zeolite frameworks,FOCUSwas modified to accommodate electron diffraction data. The modified program was applied successfully to five different data sets (four ADT and one RED) collected on zeolites of different complexities. One of these could not be solved completely by direct methods but emerged easily in theFOCUStrials.

scholarly journals High-throughput continuous rotation electron diffraction data acquisition via software automation

2018 ◽  
Vol 51 (6) ◽  
pp. 1652-1661 ◽  
Author(s):  
Magdalena Ola Cichocka ◽  
Jonas Ångström ◽  
Bin Wang ◽  
Xiaodong Zou ◽  
Stef Smeets
Keyword(s):  
Electron Diffraction ◽  
Data Collection ◽  
High Throughput ◽  
Diffraction Data ◽  
Human Error ◽  
Electron Diffraction Data ◽  
Transmission Electron ◽  
Electron Diffraction Technique ◽  
Continuous Rotation ◽  
Crystal Electron

Single-crystal electron diffraction (SCED) is emerging as an effective technique to determine and refine the structures of unknown nano-sized crystals. In this work, the implementation of the continuous rotation electron diffraction (cRED) method for high-throughput data collection is described. This is achieved through dedicated software that controls the transmission electron microscope and the camera. Crystal tracking can be performed by defocusing every nth diffraction pattern while the crystal rotates, which addresses the problem of the crystal moving out of view of the selected area aperture during rotation. This has greatly increased the number of successful experiments with larger rotation ranges and turned cRED data collection into a high-throughput method. The experimental parameters are logged, and input files for data processing software are written automatically. This reduces the risk of human error, and makes data collection more reproducible and accessible for novice and irregular users. In addition, it is demonstrated how data from the recently developed serial electron diffraction technique can be used to supplement the cRED data collection by automatic screening for suitable crystals using a deep convolutional neural network that can identify promising crystals through the corresponding diffraction data. The screening routine and cRED data collection are demonstrated using a sample of the zeolite mordenite, and the quality of the cRED data is assessed on the basis of the refined crystal structure.

scholarly journals Total-Scattering Pair-Distribution Function of Organic Material from Powder Electron Diffraction Data

2014 ◽  
Vol 21 (2) ◽  
pp. 459-471 ◽  
Author(s):  
Tatiana E. Gorelik ◽  
Martin U. Schmidt ◽  
Ute Kolb ◽  
Simon J. L. Billinge
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Distribution Function ◽  
Electron Diffraction ◽  
Diffraction Data ◽  
Pair Distribution Function ◽  
Copper Phthalocyanine ◽  
Scattering Data ◽  
Electron Diffraction Data ◽  
Transmission Electron

AbstractThis paper shows that pair-distribution function (PDF) analyses can be carried out on organic and organometallic compounds from powder electron diffraction data. Different experimental setups are demonstrated, including selected area electron diffraction and nanodiffraction in transmission electron microscopy or nanodiffraction in scanning transmission electron microscopy modes. The methods were demonstrated on organometallic complexes (chlorinated and unchlorinated copper phthalocyanine) and on purely organic compounds (quinacridone). The PDF curves from powder electron diffraction data, called ePDF, are in good agreement with PDF curves determined from X-ray powder data demonstrating that the problems of obtaining kinematical scattering data and avoiding beam damage of the sample are possible to resolve.

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