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1
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Growth Processes of ZnTe Epilayers Deposited by MBE on GaAs(100) Vicinal Surfaces - Studies by Static and Dynamic RHEED

100%
Sadowski J., Dziuba Z., Iierman M. A.
Acta Physica Polonica A
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1995
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vol. 87
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issue 1
225-228
EN
Static and dynamic reflection high energy electron diffraction (RHEED) has been applied for studying the initial growth processes of ZnTe crystallized by molecular beam epitaxy (MBE) on vicinal surfaces of GaAs(100) sub­strates. Atomically smooth ZnTe epilayers have been grown by MBE when in situ thermal desorption of the substrate protecting oxide layer was per­formed in the ultra high vacuum environment of the vacuum growth chamber just before the growth of ZnTe started. By gradual increasing of the substrate temperature of the crystallized ZnTe epilayers from 300°C to 420°C, when recording the RHEED intensity oscillations at these and eleven intermittent temperatures, it has been shown that the transition from the 2D-nucleation growth mechanism to the step-flow growth mechanism of ZnTe occurs at 410°C. Measuring periods of RHEED intensity oscillations recorded during the MBE growth processes it has been demonstrated that the growth rate of ZnTe at constant fluxes of the constituent elements decreases with increasing temperature from 0.37 ML/s at 300°C to 0.22 ML/s at 400°C.
2
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MBE Growth of YbTe on GaAs(100) and BaF_{2}(111) Substrates

100%
Sadowski J., Dynowska E., Kowalczyk L.
Acta Physica Polonica A
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1995
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vol. 88
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issue 5
1028-1032
EN
The structural properties of MBE grown YbTe layers were investigated by X-ray diffraction methods and photoluminescence measurements. YbTe films were grown on the ZnTe and CdTe buffer layers crystallised on the GaAs(100) 2° off oriented substrates and on the BaF_{2}(100) substrates. In the case of GaAs substrates the two-dimensional growth mode of YbTe was observed on reflection high energy electron diffraction picture. Results of the X-ray rocking curve and photoluminescence excitation measurements indicate that the structural properties of YbTe films are comparable to the properties of the MBE grown ZnTe and CdTe layers on the GaAs(100) substrates. The measured values of the YbTe lattice constant parallel and perpendicular to the growth plane show that the 1 μm thick layers are partially strained. The full width at half maximum values of the X-ray rocking curves are the smallest (900 arc seconds) for the YbTe films crystallised on the 2 μm thick CdTe bucher layer grown on the GaAs(100) substrate. In the case of BaF_{2}(111) substrate the two-dimensional MBE growth mode of YbTe was not observed.
3
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The Influence of the Temperature, External Magnetic Field, and the Thickness of Pt Sublayer on the Magnetocrystalline Anisotropy Constants in Co/Pt Multilayers

100%
Louail L., Azizi A., Moula B., Maouche D.
Acta Physica Polonica A
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2000
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vol. 98
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issue 6
705-713
EN
In this paper we present the behaviour of the magnetocrystalline anisotropy constants of [Co_{32Å}Pt_{xÅ}]_{6} multilayers as a function of temperature, external magnetic field, and non-magnetic layer thickness, observed by means of a torque magnetometer in an in-plane configuration. We have determined the magnetocrystalline anisotropy constants from the magnetic torque curves for different temperatures and in different magnetic fields, taking into account the angle difference between the directions of the external field and the magnetization. Among the results of this paper there are the determination of the critical thickness of Pt and the need to introduce the third order anisotropy constant in the analysis.
4
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Structural and Electrical Properties of Low Concentration SnTe Layers and PbTe/SnTe Heterostructures Grown by MBE

100%
Sadowski J., Grodzicka E., Dynowska E., Adamczewska J., Domagała J., Przedpelski W.
Acta Physica Polonica A
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1997
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vol. 92
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issue 5
967-970
EN
We analyse properties of thin SnTe layers and PbTe/SnTe heterostructures grown by MBE on BaF_{2}(111) substrates. Reflection high energy electron diffraction patterns registered during MBE growth of the samples as well as post-growth X-ray diffraction measurements evidence a high structural perfection of 0.6 μm thick SnTe layers and (50 Å PbTe)/(50 Å SnTe) superlattices. The full width at half maximum values of (222) X-ray rocking curves measured for these thin SnTe layers crystallized in the optimal MBE growth conditions are about 300 arcsec; the carrier concentrations can be tuned from 5×10^{19} cm^{-3} to 10^{2 1} cm^{-3} depending on the MBE process parameters.
5
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MBE Growth and Properties of ZnYbTe Layers

100%
Sadowski J., Szamota-Sadowska K., Świątek K., Kowalczyk L., Abounadi A., Rajira A.
Acta Physica Polonica A
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1996
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vol. 90
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issue 5
1060-1064
EN
The MBE grown ZnYbTe layers were characterized by X-ray diffraction, photoluminescence and reflectivity measurements. The MBE growth conditions allowing to obtain monocrystalline ZnYbTe layers were found to be metal-rich (MBE growth with excess of Zn flux). In optical measurements (photoluminescence, reflectivity), both transitions connected with ternary ZnYbTe compound and with Yb^{3+} ions were detected. The quality of ZnYbTe layers with Yb content of 3% and 1% is inferior to the quality of pure ZnTe MBE layers, which is clearly seen in the results of photoluminescence and reflectivity measurements. In the ZnYbTe layers with 3% Yb, exhibiting monocrystalline character in reflection high-energy electron diffraction and X-ray diffraction measurements, optical transitions characteristic of pure YbTe were detected. In ZnYbTe layers with 1% Yb, no transitions connected with YbTe were observed.
6
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Composition of a Clean and Sulphur Covered CuNi(100) Single Crystal Surface

80%
Godowski P. J., Marcus P.
Acta Physica Polonica A
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1995
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vol. 87
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issue 3
619-630
EN
Surface composition of the CuNi(100) single crystal in the temperature range of 893÷1073 K (620÷800°C) has been investigated using low energy electron diffraction and Auger electron spectroscopy methods. A clean sam­ple surface at moderate temperatures reveals small surface copper enrich­ment, with respect to the bulk Cu-rich composition. For example, at 1006 K (733°C) the copper surface concentration C^{s}_{Cu}, was determined from the quantitative Auger electron spectroscopy analysis as 0.91. After prolonged heating at higher temperatures, the copper surface concentration converges to the bulk value, i.e. at 1073 K (800°C), C^{s}_{Cu} = C^{b}_{Cu} = 0.87. Surface seg­regation of sulphur proceeds from (1 × 1) through p(2 × 2)S/CuNi(100) to c(2 × 2)S/CuNi(100) structures of low energy electron diffraction. In the presence of segregated sulphur the surface concentration of copper is lower.
7
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Lattice Parameter Relaxation during MBE of ZnTe/Cd_{1-x}Zn_{x}Te/Cd_{0.5}Zn_{0.5}Te Buffer Layers by RHLED and HRTEM

80%
Kret S., Karczewski G., Zakrzewski A., Dłużewski P., Dubon A., Wojtowicz T., Kossut J., Delamarre C., Laval J. Y.
Acta Physica Polonica A
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1995
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vol. 88
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issue 4
795-798
EN
The dynamics of the lattice relaxation processes were investigated us­ing a reflection of a high energy electron diffraction analysis system dur­ing growth by molecular beam epitaxy of ZnTe/Cd_{1-x}Ζn_{x}Te/Cd_{0.5}Mn_{0.5}Te buffers on GaAs substrates. The variation of the lattice parameter recorded by the high energy electron diffraction during the growth was later confirmed by an analysis of high resolution transmission electron microscopy images. We report also on an observation of oscillations of the lattice parameter during the deposition of several first layers of ZnTe on CdTe.
8
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X-Ray and Electron-Optical Characterization of ZnTe/CdTe and ZnTe/GaAs Epitaxial Layers Obtained by the MBE Method

80%
Auleytner J., Dziuba Z., Górecka J., Pełka J., Regiński K.
Acta Physica Polonica A
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1994
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vol. 86
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issue 4
567-574
EN
X-ray diffraction topography (Bragg diffraction) and X-ray rocking curve measurements were used to study the perfection and structural properties of ZnTe epitaxial layers on the CdTe and GaAs substrates. ZnTe epitaxial layers on CdTe were grown by MBE method by using a machine made in the Institute of Physics of the Polish Academy of Sciences. The ZnTe layers on GaAs were produced on the other, factory-made MBE system. The comparison between the X-ray topographical images of the substrate and epitaxial layer shows that imperfections on the substrate surface cause imperfections in the epitaxial layer. The results of double-crystal diffractometry measurements show that the perfection of the layer on the GaAs substrate is higher than that on the CdTe. The presence of microtwining in the ZnTe layer on the CdTe substrate was confirmed by RHEED measurements. The X-ray standing wave fluorescent spectra were also measured for the samples.
9
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Adsorption Properties of the Cu(115) Surface: Basic Interfaces

80%
Godowski P., Groso A., Hoffmann S., Onsgaard J.
Acta Physica Polonica A
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2010
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vol. 117
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issue 6
928-935
EN
The interfaces: K/Cu(115) and CO/Cu(115) have been characterized using surface sensitive techniques, including low energy electron diffraction and photoelectron spectroscopy. K adatoms show tendency to occupy the sites close to the step edges. At low temperature (near 125 K), after completion of two layers, potassium grows in 3D islands (the Stranski-Krastanov mode). At higher temperature, e.g. at room temperature, potassium introduces reconstruction of the substrate even at low coverages. Calibration of the alkali coverage, up to completion of the first layer, using the work function changes curve has been confirmed as a very convenient and precise procedure. The adsorbed state of CO at 130 K has been identified by registration of core levels obtained by the use synchrotron radiation photoelectron spectroscopy. The characteristics of the main 1s and satellite peaks have been analyzed in context of substrate geometry and compared with the ones of other copper planes. There are no indications of dissociative adsorption of CO, only residual carbon and oxygen were found after adsorbate desorption around 220 K. CO molecules show a strong tendency to "on top" adsorption in sites far from the step edges of the Cu(115) surface.
10
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X-Ray and Electron-Optical Characterization of ZnSe(Co) Crystal with Natural Face

80%
Auleytner J., Domagała J., Gołacki Z., Pawłowska M., Pełka J., Regiński K.
Acta Physica Polonica A
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1993
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vol. 83
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issue 6
759-768
EN
Using complementary X-ray and electron-optical methods, a ZnSe(Co) crystal with natural face was investigated. X-ray diffraction methods such as double-crystal X-ray reflection topography, double-crystal diffractometry for rocking curve measurements, precise lattice constant measurements by the Bond technique were used for crystal structure characterization and X-ray fluorescence method for studies of chemical composition along the crystal. The scanning electron microscopic image of the crystal surface and reflection diffraction of the high-energy electrons enriched the crystal structure characterization. It was shown that X-ray characterization and reflection high-energy electron diffraction can be regarded as very important complementary tools for non-destructive investigation of the ZnSe(Co) crystal surface layers.
11
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Strain Relaxation of ZnTe/CdTe and CdTe/ZnTe heterostructures: In Situ Study

80%
Riesz F., Kret S., Karczewski G., Wojtowicz T., Kossut J.
Acta Physica Polonica A
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1996
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vol. 90
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issue 5
911-914
EN
The strain relaxation kinetics of ZnTe/CdTe and CdTe/ZnTe heterostructures grown on GaAs substrates by molecular beam epitaxy are studied by in situ reflection high-energy electron diffraction. The observed critical layer thickness is 5 monolayers for ZnTe/CdTe and less than 1 monolayer for CdTe/ZnTe. The relaxation is anisotropic. Dislocation core parameters and relaxation rate constants were determined using a kinetic model and assuming strain-dependent activation energy of dislocation movement.
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