Contrasts of planar defects in reflection electron microscopy

1993 ◽  
Vol 51 ◽  
pp. 1004-1005
Author(s):  
Feng Tsai ◽  
J. M. Cowley
Keyword(s):  
Electron Microscopy ◽  
Surface Defects ◽  
Practical Importance ◽  
Theoretical Treatment ◽  
Crystal Surfaces ◽  
Planar Defects ◽  
Surface Steps ◽  
Surface Reconstructions ◽  
Domain Boundaries ◽  
Reflection Electron Microscopy

Reflection electron microscopy (REM) has been used to study surface defects such as surface steps, dislocations emerging on crystal surfaces, and surface reconstructions. However, only a few REM studies have been reported about the planar defects emerging on surfaces. The interaction of planar defects with surfaces may be of considerable practical importance but so far there seems to be only one relatively simple theoretical treatment of the REM contrast and very little experimental evidence to support its predications. Recently, intersections of both 90° and 180° ferroelectric domain boundaries with BaTiO3 crystal surfaces have been investigated by Tsai and Cowley with REM.The REM observations of several planar defects, such as stacking faults and domain boundaries have been continued by the present authors. All REM observations are performed on a JEM-2000FX transmission electron microscope. The sample preparations may be seen somewhere else. In REM, the incident electron beam strikes the surface of a crystal with a small glancing angle.

Observation of ferroelectric domain boundaries in BaTiO3 with REM

1992 ◽  
Vol 50 (1) ◽  
pp. 360-361
Author(s):  
Feng Tsal
Keyword(s):  
Electron Microscopy ◽  
Surface Defects ◽  
Ferroelectric Material ◽  
Crystal Surfaces ◽  
Etching Technique ◽  
Surface Steps ◽  
Transmission Electron ◽  
Domain Boundaries ◽  
Reflection Electron Microscopy ◽  
Etched Surface

The earlier work of transmission electron microscopy(TEM) on ferroelectric domains have been concentrated on the studies of domain configurations and contrast theory, Scanning electron microscopy(SEM) is also used to study ferroelectric material surfaces and has revealed various domain boundaries on the chemical-etched surface of BaTiO3. However, the method is destructive and largely dependent on the etching technique. Reflection electron microscopy (REM) has recently been developed to study crystal surfaces, especially the surface defects such as surface steps and emerging dislocations. This paper presents the observation of 90° domain boundaries in BaTiO3 single crystal with REM and concentrates on the contrast of 90° domain boundaries.

Reflection electron microscopy of ferroelectric domains

1994 ◽  
Vol 52 ◽  
pp. 568-569
Author(s):  
Feng Tsai ◽  
J. M. Cowley
Keyword(s):  
Electron Microscopy ◽  
Surface Defects ◽  
Crystal Surface ◽  
Dark Field ◽  
Ferroelectric Domain ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Crystal Surfaces ◽  
Domain Boundaries ◽  
Reflection Electron Microscopy

The intersections of ferroelectric domain boundaries with crystal surfaces have been studied by optical microscopy. The method is widely used but usually of low resolution. Transmission electron microscopy (TEM) can provide high-resolution images but may not be appropriate for studying crystal surfaces. Scanning electron microscopy (SEM) has also been used to study the intersections of ferroelectric domain boundaries with the surfaces of ferroelectric crystals. However, the resolution is still low and is destructive if an etched crystal surface is used. Other alternatives have also been attempted to study ferroelectric domain boundaries on surfaces, such as scanning tunneling microscopy (STM), atomic force microscopy (AFM). But, no reports have been known so far.On the other hand, reflection electron microscopy (REM), as a branch of dark-field imaging technique dedicated for surface studies in TEM, has been developed to study crystal surfaces, surface reconstruction and surface defects with a resolution of about 10Å. It has been considered as a powerful technique to study surface defects and may be used to study the ferroelectric domain boundaries emerging on surfaces.

Reflection Electron Microscopy and Diffraction from Crystal Surfaces

1983 ◽  
Vol 31 ◽  
Author(s):  
J.M. Cowley
Keyword(s):  
Electron Microscopy ◽  
Surface Structure ◽  
Crystal Surfaces ◽  
Local Composition ◽  
Surface Steps ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Reflection Electron Microscopy ◽  
Electron Microscopes ◽  
Geometric Effects

ABSTRACTThe recent revival of techniques for the imaging of crystal surfaces, using electrons forward-scattered in the RHEED mode and employing modern electron microscopes, has lead to the introduction of valuable new methods for the study of surface structure. Either fixed beam or scanning transmission electron microscopy (STEM) instruments may be used and in each case a lateral resolution of 10Å or better is possible. Simple theoretical treatments suggest that the contrast from surface steps may be attributed to a combination of phase-contrast, diffraction contrast and geometric effects. With a STEM instrument the image information can be combined with information on the local composition and crystal structure by use of microanalysis and microdiffraction techniques. Examples of applications include studies of the surface structure of metals, semiconductors and oxides, and the surface reactions.

High Resolution Imaging of As-Grown Sapphire Surfaces

1985 ◽  
Vol 62 ◽  
Author(s):  
Tung Hsu ◽  
S. R. Nutt
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Structural Features ◽  
High Resolution Imaging ◽  
Sapphire Surface ◽  
Surface Steps ◽  
Transmission Electron ◽  
Reflection Electron Microscopy ◽  
Resolution Imaging ◽  
Surface Facets

ABSTRACTSurfaces of commercially grown edge-defined film-fed growth sapphire (EFG α-Al2O3) were studied in the electron microscope using both reflection electron microscopy (REM) and conventional transmission electron microscopy (TEM). The as-grown sapphire surface, ostensibly {1120}, was characterized by “rooftop” structures which were often locally periodic. These rooftop structures consisted of alternating {1120} facets and additional facets inclined a few degrees. The crystallography of the surface facets was analyzed using REM imaging of bulk specimens, and trace analysis of back-thinned plan section TEM specimens. Surface roughness was measured by stylus profilometry. and these measurements were compared to the electron microscopy observations. Fine structural features parallel to <0110> directions were also observed in both REM and TEM experiments, and these were attributed to surface steps of atomic scales.

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.

REM Studies of Adsorption-Induced Phase Transitions and Faceting in the Si(111)-Au System

1998 ◽  
Vol 05 (03n04) ◽  
pp. 653-663 ◽  
Author(s):  
Koyu Aoki ◽  
Hiroki Minoda ◽  
Yasumasa Tanishiro ◽  
Katsumichi Yagi
Keyword(s):  
Electron Microscopy ◽  
Phase Transitions ◽  
Surface Structure ◽  
Lower Side ◽  
Domain Boundaries ◽  
Adsorption Processes ◽  
Reflection Electron Microscopy ◽  
Step Down ◽  
Successive Phase

Initial stages of Au adsorption processes on Si(111)-(7 × 7) surfaces at ~780°C, a temperature range where the surface structure undergoes successive phase transitions [(7 × 7)–("1 × 1")–(5×2)–("1 × 1")], were observed in situ by reflection electron microscopy. All of the phase transitions are heterogeneous on the surface and start at surface atomic steps. During Au adsorption on Si(111)-(7 × 7), and subsequently on Si(111)-("1 × 1") surface with wide terraces, steps advance toward the step-down direction. At a Au coverage of ~0.3 ML, the 5 × 2 structure nucleates at step edges, and the nuclei expand both to the lower side terraces and to the higher side terraces. At this stage, an effect of current for heating the specimen was noted. From measurements of such movements of the steps and the domain boundaries, the density of Si atoms in the "1 × 1" phase is estimated to be 1.3–1.7 ML at a Au coverage of ~0.3 ML. Au adsorption on Si(111) surfaces with narrow terraces causes bunching of the steps. After nucleation of the 5 × 2 structure, the bunched [Formula: see text] steps become straight along the [Formula: see text] direction, and are transformed into the (335) facet planes at a Au coverage of 0.50 ML. It was found that the (335) facet planes are stabilized by adsorbed Au atoms. Destruction of the (335) facet is noted at a Au coverage of 0.73 ML.

Reflection Electron Microscopy

1975 ◽  
Vol 33 ◽  
pp. 122-123
Author(s):  
P. E. Højlund Nielsen ◽  
J. M. Cowley
Keyword(s):  
Electron Microscopy ◽  
Single Crystal ◽  
Chromatic Aberration ◽  
Dark Field ◽  
Energy Spread ◽  
Crystal Surfaces ◽  
Single Crystal Surfaces ◽  
Dark Field Imaging ◽  
Reflection Electron Microscopy ◽  
Field Imaging

Reflection electron microscopy was widely used before 1960 for the study of surfaces. For the imaging diffuse scattered electrons was applied. For avoiding a severe foreshortening the surface was illuminated and viewed at fairly large angles. That resulted in a large energy spread of the scattered electrons so the resolution was limited to about 500Å due to chromatic aberration. Since such a resolution could be achieved more readily in scanning microscopes, the method was abandoned. However for single crystal surfaces the situation is entirely different. If the surface can be maintained reasonably clean, strong diffraction spots can be obtained and the energy spread in the diffracted beam is usually small; thus the imaging of the surface can be performed in a manner similar to the dark field imaging of a thin crystalline specimen.

Nucleation, Cluster Growth, and Structure of Crystalline C60 and C70

1992 ◽  
Vol 270 ◽  
Author(s):  
Nan Yao ◽  
S. K. Behal ◽  
C. F. Klein ◽  
M. M. Disko ◽  
S. C. Fung ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Strain Field ◽  
Surface Defects ◽  
Surface Strain ◽  
Cluster Growth ◽  
Twin Structure ◽  
Transmission Electron ◽  
Initial Nucleation ◽  
Reflection Electron Microscopy ◽  
Diffraction Patterns

ABSTRACTThe nucleation and cluster growth of C60 and C70 crystallites on various substrates at ambient temperature have been investigated using electron microscopy. It was found that the initial nucleation is closely associated with surface defects, and the fullerenes are much more strongly bonded to each other than to the substrate. Sublimed C60 or C70 crystallites nucleate at the step edge in the liquid state and are aligned with the step walls and terraces through the process of coalescence. Reflection Electron Microscopy (REM) studies have shown an abnormal profile of C60 grown crystals as a result of the interaction of C60 molecules with the surface strain field during crystal growth. Transmission electron diffraction patterns reveal a twin structure with (110) habit plane for the low temperature ordered phase.

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