High Resolution Scanning Electron Microscopy of Surfaces

1990 ◽  
Vol 48 (1) ◽  
pp. 296-297
Author(s):  
J.M. Cowley
Keyword(s):  
Electron Microscopy ◽  
Small Diameter ◽  
Low Energy ◽  
X Rays ◽  
Resolution Limit ◽  
Secondary Electrons ◽  
Surface Features ◽  
Surface Steps ◽  
Reflection Electron Microscopy

Electron beams of small diameter, generated with field emission guns may be used to investigate surfaces in many different ways. Images may be formed in the scanning mode by use of the elastically, or quasi-elastically scattered electrons or by the detection of secondary radiation including low energy secondary electrons, Auger electrons and X-rays. Except in the case of low-energy secondary electrons, high spatial resolution has not yet been achieved by detection of the secondary radiations so these imaging modes will not be discussed here.The scanning modes used with the detection of elastic or quasi-elastic electrons in a dedicated STEM instrument are analogous to those used in conventional TEM instruments for surface studies, such as profile imaging and reflection electron microscopy. In each case, the practical limitations of current STEM systems tend to limit the quality of the imaging but the flexibility of the STEM detector system has provided several important advantages. In scanning reflection microscopy (SREM) the resolution attained is comparable with that for REM. The important advantage over REM is that microdiffraction patterns may be obtained from any surface features as small as the resolution limit for imaging. Also it is relatively easy to make use of the surface channelling conditions in order to enhance the contrast of surface steps or other surface features.

The annealed (0001) α-alumina surface and its influence on thin-film growth

1995 ◽  
Vol 53 ◽  
pp. 336-337
Author(s):  
Michael W. Bench ◽  
Paul G. Kotula ◽  
C. Barry Carter
Keyword(s):  
Electron Microscopy ◽  
Surface Energy ◽  
Film Growth ◽  
Thin Film Growth ◽  
Energy Calculations ◽  
Transmission Electron ◽  
Reflection Electron Microscopy ◽  
Low Energy Electron ◽  
Surface Nature

The growth of semiconductors, superconductors, metals, and other insulators has been investigated using alumina substrates in a variety of orientations. The surface state of the alumina (for example surface reconstruction and step nature) can be expected to affect the growth nature and quality of the epilayers. As such, the surface nature has been studied using a number of techniques including low energy electron diffraction (LEED), reflection electron microscopy (REM), transmission electron microscopy (TEM), molecular dynamics computer simulations, and also by theoretical surface energy calculations. In the (0001) orientation, the bulk alumina lattice can be thought of as a layered structure with A1-A1-O stacking. This gives three possible terminations of the bulk alumina lattice, with theoretical surface energy calculations suggesting that termination should occur between the Al layers. Thus, the lattice often has been described as being made up of layers of (Al-O-Al) unit stacking sequences. There is a 180° rotation in the surface symmetry of successive layers and a total of six layers are required to form the alumina unit cell.

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.

Modified Nextal crystallization device forin situinspection of protein crystal quality

2005 ◽  
Vol 38 (2) ◽  
pp. 396-397 ◽  
Author(s):  
Nobuhisa Watanabe
Keyword(s):  
Crystal Quality ◽  
Protein Crystal ◽  
X Rays ◽  
Resolution Limit ◽  
Physical Damage ◽  
Space Group ◽  
Cell Parameters

The modification and use of the Nextal crystallization device for checking the diffraction quality of protein crystalsin situis described. Using the modified device, crystals in the crystallization drop can be exposed to X-rays directly to observe the diffraction quality without physical damage to the crystal. If the crystals in the drop are well separated, not only the resolution limit of the crystal is estimated, but also determination of the space group and the cell parameters is possible.

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.

Energy-filtered reflection electron microscopy and reflection high-energy electron diffraction on Zeiss 912 TEM

1993 ◽  
Vol 51 ◽  
pp. 580-581
Author(s):  
JINGYUE LIU
Keyword(s):  
Electron Microscopy ◽  
Electron Diffraction ◽  
Ccd Camera ◽  
Chromatic Aberration ◽  
High Energy ◽  
Energy Electron ◽  
Objective Lens ◽  
High Energy Electron ◽  
Resolution Limit ◽  
Reflection Electron Microscopy

In reflection electron microscopy (REM) and reflection high energy electron diffraction (RHEED) the average path length of the elastically scattered electrons in the crystal ranges from 10 -100 nm and a significant portion of the electrons in the RHEED pattern spots used for imaging is inelastically scattered. The excitations of surface plasmons, bulk plasmons and valence electrons involves energy losses of 10 ∽30 eV. Thus the image contrast and resolution in REM are degraded due to chromatic aberration of the objective lens. The use of energy filters in a TEM should offer significant improvement in resolution and contrast of REM images. We present here some new results on the investigation of resolution limit and contrast mechanisms in energy filtered REM images.The experiments were performed on a Zeiss 912 TEM fitted with an Omega magnetic imaging energy filter. Digital RHEED patterns and REM images were acquired into 1024 pixels by 1024 pixels via a Gatan 679 CCD camera fitted to the microscope.

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.

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