Algorithms for determining the phase of RHEED oscillations

2015 ◽  
Vol 48 (6) ◽  
pp. 1927-1934 ◽  
Author(s):  
Zbigniew Mitura ◽  
Sergei L. Dudarev
Keyword(s):  
Experimental Data ◽  
Direct Method ◽  
Incident Beam ◽  
Diffraction Theory ◽  
High Energy ◽  
Angle Of Incidence ◽  
High Energy Electron ◽  
Dynamical Diffraction ◽  
Glancing Angle ◽  
Low Symmetry

Oscillations of reflection high-energy electron diffraction (RHEED) intensities are computed using dynamical diffraction theory. The phase of the oscillations is determined using two different approaches. In the first, direct, approach, the phase is determined by identifying the time needed to reach the second oscillation minimum. In the second approach, the phase is found using harmonic analysis. The two approaches are tested by applying them to oscillations simulated using dynamical diffraction theory. The phase of RHEED oscillations observed experimentally is also analysed. Experimental data on the variation of the phase as a function of the glancing angle of incidence, derived using the direct method, are compared with the values computed using both the direct and harmonic methods. For incident-beam azimuths corresponding to low-symmetry directions, both approaches produce similar results.

Computer Investigations of Features of RHEED Oscillations for GaAs and for Ge

2013 ◽  
Vol 203-204 ◽  
pp. 347-350
Author(s):  
Zbigniew Mitura
Keyword(s):  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Incident Beam ◽  
Diffraction Theory ◽  
Oscillation Phase ◽  
Dynamical Diffraction ◽  
Wide Range ◽  
Glancing Angle ◽  
Scattering Potential ◽  
Experimental Findings

During molecular beam epitaxy regular oscillations of the intensity of the specularly reflected beam often occur. The phenomenon of such oscillations is still theoretically explained only partially. For example it is not clear why usually the oscillation phase depends strongly on the glancing angle of the incident beam. However, quite recently interesting results were shown in the literature on the features of RHEED oscillations observed during the growth of Ge layers. The phase of oscillations practically stays constant for a wide range of angles. So in this paper, we show results of RHEED dynamical calculations for Ge. They are presented together with results of calculations for GaAs to make analysis executed more complete. It is concluded that experimental findings for Ge for off-symmetry azimuths can be explained using dynamical diffraction theory employing the proportional model (for which the scattering potential of the layer is determined as the potential of the completed layer multiplied by the coverage).

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.

Computer studies on reflection high-energy electron diffraction from the growing surface of Ge(001)

2013 ◽  
Vol 46 (4) ◽  
pp. 1024-1030 ◽  
Author(s):  
Zbigniew Mitura
Keyword(s):  
Experimental Data ◽  
Electron Diffraction ◽  
High Energy ◽  
Bloch Wave ◽  
Energy Electron ◽  
High Energy Electron ◽  
Homoepitaxial Growth ◽  
Scattering Potential ◽  
Computer Studies ◽  
Quantitative Explanation

The results of calculations of reflection high-energy electron diffraction intensities, measured at different stages of the homoepitaxial growth of Ge(001), are described. A two-dimensional Bloch wave approach was used in calculations of the Schrödinger equation with a one-dimensional potential. The proportional model was used for partially filled layers,i.e.the scattering potential was taken to be proportional to the coverage and the potential of the fully filled layer. Using such an approach, it was shown that it is possible to obtain valuable information for the analysis of experimental data. The results of these calculations were compared with data for off-symmetry azimuths from the literature, and satisfactory agreement between the theoretical and experimental data was found. Also assessed was whether developing more advanced models (i.e.going beyond the proportional model), to make a more detailed account of the diffuse scattering, might be important in achieving a fully quantitative explanation of the experimental data.

scholarly journals LAYERED IN2SE3 ON SI (111) SURFACE WITH HYSTERESIS OF THE TEMPERATURE DEPENDENCE OF RESISTANCE

2020 ◽  
Author(s):  
Sergei Ponomarev ◽  
Dmitry Rogilo
Keyword(s):  
Experimental Data ◽  
Temperature Dependence ◽  
High Energy ◽  
Temperature Decrease ◽  
Two Dimensional ◽  
Film Resistance ◽  
High Energy Electron ◽  
Rate Reduction ◽  
Abrupt Decrease ◽  
Reverse Transition

In this work, the methods of controlled growth of two-dimensional In2Se3 on a Si (111) substrate were studied by reflection high-energy electron diffraction (RHEED). According to experimental data, the deposition rate reduction increases the size of two-dimensional In2Se3 islands. The temperature dependence of the film resistance was measured by the two-contact technique. At temperature decrease near T = 140 K, an abrupt decrease in resistance by a factor of ~ 1000 was found. The reverse transition occurs near T = 180 K. At T = 20–40 K the second hysteresis occurring without the film resistance jump was found.

Image Degeneration by Charging Effects on Photographic Media

1969 ◽  
Vol 27 ◽  
pp. 132-133
Author(s):  
J. H. Reisner ◽  
J. A. Horner
Keyword(s):  
Electron Beam ◽  
Electrostatic Field ◽  
Effective Charge ◽  
Incident Beam ◽  
High Energy ◽  
Energy Electron ◽  
High Energy Electron ◽  
Conducting Surface ◽  
Charge Center

Insulators irradiated by a high energy electron beam in vacuum become charged positively. The charging produces an electrostatic field which causes the incident beam to be deflected progressively toward the effective charge center. Photographic materials are essentially dielectrics and exhibit charge phenomena which can disturb an image. The charging conditions are aggravated by suspending the photo material remotely from ground, or a conducting surface.

Dynamical calculations for RHEED from MBE growing surfaces. II. Growth interruption and surface recovery

1991 ◽  
Vol 435 (1894) ◽  
pp. 257-267 ◽  
Keyword(s):  
Surface Roughness ◽  
Molecular Beam ◽  
High Energy ◽  
High Energy Electron ◽  
Intensity Oscillation ◽  
Recovery Curves ◽  
Quantitative Studies ◽  
Growth Interruption ◽  
Glancing Angle ◽  
Diffraction Condition

Detailed dynamical calculations for reflection high-energy electron diffraction (RHEED) from surfaces growing by molecular beam epitaxy have been made to investigate the technique of growth interruption and surface recovery kinetics. A birth-death growth model and a systematic reflection approximation to RHEED have been used. It is found that whilst the RHEED intensity oscillation behaviour is very sensitive to the incident glancing angle, the shape of the intensity recovery curve is insensitive to the diffraction condition. It is further shown that the RHEED intensity recovery curves bear a resemblance to the corresponding surface-roughness recovery curves. Sensible quantitative studies of recovery can therefore be made by analysing the RHEED intensity recovery curves. A similarity between the surface recovery and RHEED intensity recovery has been established.

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