STRUCTURAL ANALYSIS OF IMPERFECT CRYSTAL SURFACES BY REFLECTION HIGH-ENERGY ELECTRON DIFFRACTION: ANTIPHASE DOMAINS OF A ${\rm Si}(111)(\sqrt 3 \times\sqrt 3)$-Ag SURFACE

1997 ◽  
Vol 04 (05) ◽  
pp. 985-990
Author(s):  
AYAHIKO ICHIMIYA ◽  
YUSUKE OHNO
Keyword(s):  
Electron Diffraction ◽  
Fourier Coefficients ◽  
High Energy ◽  
Energy Electron ◽  
High Energy Electron ◽  
Crystal Surfaces ◽  
Domain Structures ◽  
Imperfect Crystal ◽  
Structure Determinations ◽  
Antiphase Domains

For dynamical calculations of reflection high-energy electron diffraction (RHEED) for imperfect crystal surfaces, a general formula of Fourier coefficients of crystal potential with domain structures is developed. Using the formula, RHEED intensity rocking curves are calculated for a [Formula: see text]-Ag surface with antiphase domains. We discuss effects of antiphase domains of surfaces in structure determinations by RHEED.

COMPUTATIONAL THEORY OF REFLECTION HIGH ENERGY ELECTRON DIFFRACTION

1997 ◽  
Vol 04 (03) ◽  
pp. 513-524 ◽  
Author(s):  
P. A. MAKSYM
Keyword(s):  
Electron Diffraction ◽  
High Energy ◽  
Energy Electron ◽  
Alternative Methods ◽  
Computational Techniques ◽  
Computational Technique ◽  
High Energy Electron ◽  
Crystal Surfaces ◽  
Computational Theory ◽  
The Individual

The theory of reflection high energy electron diffraction (RHEED) by crystal surfaces is reviewed, with special emphasis on computational techniques. Multiple scattering is accounted for by solving the Schrödinger equation exactly to obtain the amplitudes of the diffracted beams above the surface. The surface and substrate are divided into atomic layers and the RHEED intensities for the entire system are determined from the scattering properties of the individual layers. Alternative methods for implementing this approach are explained and compared. Recent applications to analysis of real RHEED data are used to illustrate the general theory and it is shown that it can provide very good agreement with experiment. The computational efficiency of RHEED calculations is examined carefully and key bottlenecks are identified. This leads to a new computational technique which is much faster than existing ones. Some problems connected with the implementation of this approach are examined in detail.

STRUCTURAL ANALYSIS OF CRYSTAL SURFACES BY REFLECTION HIGH ENERGY ELECTRON DIFFRACTION

1997 ◽  
Vol 04 (03) ◽  
pp. 501-511 ◽  
Author(s):  
AYAHIKO ICHIMIYA ◽  
YUSUKE OHNO ◽  
YOSHIMI HORIO
Keyword(s):  
Electron Diffraction ◽  
Surface Structure ◽  
Forward Direction ◽  
High Energy ◽  
Zone Axis ◽  
Energy Electron ◽  
High Energy Electron ◽  
Structure Determinations ◽  
The One ◽  
Diffraction Condition

For surface structure determinations by reflection high energy electron diffraction (RHEED), intensity rocking curves are analyzed through RHEED dynamical calculations. Since fast electrons are scattered dominantly in the forward direction by atoms, dynamic diffraction mainly occurs in the forward direction. By the use of this feature, it is possible to choose a diffraction condition under which electrons are diffracted mainly by lattice planes parallel to the surface, when the incident direction is chosen at a certain azimuthal angle with respect to a crystal zone axis. This diffraction condition is called the one-beam condition. Under this condition, the RHEED intensity is a function of interlayer distances and atomic densities of the surface layers. Therefore the surface normal components of the atomic positions are determined by analysis of the one-beam rocking curve using a RHEED dynamical calculation. Then, using the result of the surface normal components of atomic positions, lateral positions of the surface atoms are determined from analysis of the rocking curves at many-beam conditions, where the direction of the incident beam is chosen along a certain crystal zone axis. An example of the surface structure determination of a Si(111) surface at high temperatures is reported. We discuss effects of terraces and antiphase domains of surfaces in structure determinations by RHEED.

Kinematic Approximations in TED and RHEED Analysis of Reconstructed Surfaces

1990 ◽  
Vol 48 (2) ◽  
pp. 396-397
Author(s):  
L. -M. Peng ◽  
M. J. Whelan
Keyword(s):  
Electron Diffraction ◽  
Kinematic Analysis ◽  
Incident Beam ◽  
High Energy ◽  
Energy Electron ◽  
Great Success ◽  
High Energy Electron ◽  
Kinematic Approximation ◽  
Reconstructed Surfaces

In recent years there has been a trend in the structure determination of reconstructed surfaces to use high energy electron diffraction techniques, and to employ a kinematic approximation in analyzing the intensities of surface superlattice reflections. Experimentally this is motivated by the great success of the determination of the dimer adatom stacking fault (DAS) structure of the Si(111) 7 × 7 reconstructed surface.While in the case of transmission electron diffraction (TED) the validity of the kinematic approximation has been examined by using multislice calculations for Si and certain incident beam directions, far less has been done in the reflection high energy electron diffraction (RHEED) case. In this paper we aim to provide a thorough Bloch wave analysis of the various diffraction processes involved, and to set criteria on the validity for the kinematic analysis of the intensities of the surface superlattice reflections.The validity of the kinematic analysis, being common to both the TED and RHEED case, relies primarily on two underlying observations, namely (l)the surface superlattice scattering in the selvedge is kinematically dominating, and (2)the superlattice diffracted beams are uncoupled from the fundamental diffracted beams within the bulk.

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