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.

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.

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.

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.

Surface resonance channelling in scanning reflection electron microscopy

1988 ◽  
Vol 46 ◽  
pp. 692-693
Author(s):  
J.M. Cowley ◽  
P.A. Crozier
Keyword(s):  
Electron Microscopy ◽  
Crystal Surface ◽  
Scanning Transmission Electron Microscope ◽  
Diffraction Effect ◽  
Transmission Electron ◽  
Surface Resonance ◽  
Scanning Transmission ◽  
Reflection Electron Microscopy ◽  
Resolution Imaging ◽  
Electron Energy Loss

The phenomena of the channelling of electrons along planes or rows of atoms in the surface layers of crystals has been investigated recently in relation to microdiffraction and RHEED, REM, (reflection electron microscopy) and REELS (reflection electron energy loss spectroscopy) by using a conventional TEM in the reflection mode.The renewed interest in this phenomenon, known for many years, is the evidence from calculations of dynamical diffraction effect at surfaces that the electrons may be channelled along the topmost layers of atoms on a crystal surface and that the RHEED, REM and REELS signals may thus be sensitive to the structure and composition of the surface layer. These techniques may therefore provide a powerful new approach to the study of surfaces in which surface microanalysis and diffraction studies may be combined with nanometer-resolution imaging.An investigation has now been made of the analogous techniques which may be applied to the study of surfaces by use of a scanning transmission electron microscope.

APPLICATIONS OF STEM INSTRUMENTS FOR SURFACE STUDIES

1997 ◽  
Vol 04 (03) ◽  
pp. 567-575 ◽  
Author(s):  
J. M. COWLEY
Keyword(s):  
Surface Structure ◽  
Standing Wave ◽  
High Efficiency ◽  
Electron Holography ◽  
X Rays ◽  
Wave Fields ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Annular Detector ◽  
Electron Microscopes

Scanning transmission electron microscopy (STEM) instruments have some particular advantages as compared with the more common transmission electron microscopes for some applications to surface research. Imaging of surfaces and mapping of the elemental distributions on surfaces with spatial resolutions approaching 1 nm are possible in an ultrahigh-vacuum STEM instrument when the low-energy secondary electrons or the Auger-emitted electrons are collected with high efficiency. In the imaging of surface layers on thin-film substrates, viewed in transmission, the use of a thin annular detector in STEM may greatly enhance the contrast, as illustrated by the case of the imaging of very thin nanocrystalline carbon layers on much thicker amorphous SiO2 films. The scanning reflection mode in a STEM instrument can provide some useful forms of contrast in images of surface structure. Standing wave fields can be formed on the surfaces of crystals with electrons, as with X-rays, one advantage of the electron case being that the standing wave fields may be imaged. Two new forms of electron holography, involving a STEM instrument and suitable for the study of surface structure, are proposed.

Dynamics of In Cluster Growth During InP(110) Surface Dissociation Studied by in-situ Reflection Electron Microscopy

1995 ◽  
Vol 404 ◽  
Author(s):  
M. Gajdardziska-Josifovska ◽  
M. H. Malay ◽  
David J. Smith
Keyword(s):  
Electron Microscopy ◽  
Contact Angle ◽  
Annealing Process ◽  
Cluster Growth ◽  
Surface Cluster ◽  
Surface Steps ◽  
Transmission Electron ◽  
Annealing Effects ◽  
Reflection Electron Microscopy

AbstractAnnealing effects on InP (110) surfaces were observed in situ using a modified ultrahighvacuum transmission electron microscope equipped with a specimen heating holder. Reflection electron microscopy (REM) was used to record the dynamics of nucleation and growth of liquid In clusters at 650°C, following the desorption of P from the surface. These droplets showed no preference for nucleation at surface steps, and the steps appeared stationary throughout the annealing process. Two distinct types of In cluster growth rates and shape evolutions were detected. A model was developed to decouple height and length information in the REM images. Contact angle and volume above the InP(110) surface were calculated from the dynamic data. The change of contact angle with time provides evidence for sub-surface cluster etching.

Electron Microscopy of Semiconductors Reconstructed Surfaces

1983 ◽  
Vol 31 ◽  
Author(s):  
Pierre M. Petroff
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electron Diffraction ◽  
Surface Reconstruction ◽  
Surface Steps ◽  
Transmission Electron ◽  
Dislocation Models ◽  
Reconstructed Surfaces ◽  
Reflection Electron Microscopy ◽  
Reconstructed Surface

ABSTRACTSurface sensitive transmission electron microscopy (SSTEM) and reflection electron microscopy (REM) have been used to analyze the Si (111) 1×1 → 7×7 surface reconstruction. The SSTEM and transmission electron diffraction results for the Si (111) 7×7 surface are interpreted using several possible “surface dislocation” models. The SSTEM and REM techniques have also been applied to the GaAs (100) MBE deposited surfaces. The rough surface topography for the c(4×4) reconstructed surface is attributed to surface steps motions and bunching upon interruption of the MBE deposition.

Reflection Electron Microscopy (REM) of Surface Steps & Dislocations on GaP(110) & GaAs(110)

1982 ◽  
Vol 40 ◽  
pp. 450-451
Author(s):  
Tung Hsu ◽  
Sumio Iijima
Keyword(s):  
Electron Microscopy ◽  
Room Temperature ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Heating Stage ◽  
Surface Steps ◽  
Reflection Electron Microscopy ◽  
Electron Microscopes ◽  
High Vacuum Environment

Reflection electron microscopy (REM) in ultra high vacuum environment with heating stage has been reported by Osakabe, et al. In this paper, we present our results in REM imaging of single steps and dislocations using commercial electron microscopes (JEM-100B and Philips-400T) under ordinary pressure (10-7 torr) and room temperature.

Reflection electron microscopy of surfaces

1986 ◽  
Vol 44 ◽  
pp. 376-379
Author(s):  
G. Lehmpfuhl ◽  
Y. Uchida
Keyword(s):  
Electron Microscopy ◽  
Surface Topography ◽  
Single Crystals ◽  
Surface Science ◽  
Surface Treatments ◽  
Surface Steps ◽  
Transmission Electron ◽  
Initial Stage ◽  
Bulk Single Crystals ◽  
Reflection Electron Microscopy

In surface science the direct imaging of the surface topography of single crystals is of great interest for the investigation of surface-changing processes. Imaging can be done in transmission electron microscopy (TEM) as well as in reflection electron microscopy (REM) using a diffracted beam with surface-sensitive intensity. Surface steps of atomic height can be imaged with both methods. The highest resolution is obtainable only in transmission; however, for the investigation of surface treatments, the reflection method from bulk single crystals is more suitable, even with a lack of resolution, since the thin TEM specimens are often not mechanically stable against surface treatments. With this technique the initial stage of epitaxy, the influence of surface reactions, corrosion etc. on the surface topography can be investigated. The application of REM requires that two important conditions be met, one concerning the specimen itself. Due to the small angle of observation the image is foreshortened.

A New Method For Calibrating Focusing Steps Of Electron Microscopes

1985 ◽  
Vol 43 ◽  
pp. 68-69
Author(s):  
Tung Hsu
Keyword(s):  
Electron Microscopy ◽  
Dark Field ◽  
New Method ◽  
Depth Of Field ◽  
Objective Lens ◽  
Focus Position ◽  
Bright Field ◽  
Surface Steps ◽  
Reflection Electron Microscopy ◽  
Electron Microscopes

Focusing steps of an electron microscope, i.e., the change of focus, Δf, corresponding to one click on any one of the focus dials must be calibrated. Two methods have been used; measuring the distance between bright field and dark field images of small crystalline particles and measuring the diameters of optical diffractograms obtained from the image of an amorphous specimen.A new method utilizing the large depth of field in reflection electron microscopy (REM) provides a direct means of measuring the focusing steps on the micrograph. The in focus area in an REM image can be recognized as the “least grainy” part or the minimum contrast of images of steps. Using surface steps, particles, or other features as References, the shift of this in focus position due to the variation of objective lens current can be readily measured on the micrograph. This distance is then converted to f by taking account of magnification (calibrated) and the foreshortening factor (calculated from the diffraction pattern).

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