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1
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Fano Resonance of Eu^{2+} and Eu^{3+} in (Eu,Gd)Te MBE Layers

100%
Orlowski B., Kowalski B., Dziawa P., Pietrzyk M., Mickievicius S., Osinniy V., Taliashvili B., Kowalik I., Story T., Johnson R.
Acta Physica Polonica A
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2005
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vol. 108
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issue 5
803-807
EN
Resonant photoemission spectroscopy, with application of synchrotron radiation, was used to study the valence band electronic structure of clean surface of (EuGd)Te layers. Fano-type resonant photoemission spectra corresponding to the Eu 4d-4f transition were measured to determine the contribution of 4f electrons of Eu^{2+} and Eu^{3+} ions to the valence band. The resonant and antiresonant photon energies of Eu^{2+} ions were found as equal to 141 V and 132 eV, respectively and for Eu^{3+} ions were found as equal to 146 eV and 132 eV, respectively. Contribution of Eu^{2+}4f electrons was found at the valence band edge while for Eu^{3+} it was located in the region between 3.5 eV and 8.5 eV below the valence band edge.
2
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Photoemission Study of Mn 3d Electrons in the Valence Band of Mn/GeMnTe

100%
Pietrzyk M., Kowalski B., Orłowski B., Knoff W., Osinniy V., Kowalik I., Story T., Johnson R.
Acta Physica Polonica A
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2007
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vol. 112
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issue 2
275-281
EN
We present the results of the electronic band structure study of Ge_{0.9}Mn_{0.1}Te epilayers, clean and modified in situ by deposition of manganese atoms. The sets of resonant photoemission spectra were measured for the photon energy range covering the energy of Mn 3p→3d transition (45
3
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Fano Resonance Investigation of PbTe Layers Containing Eu and Gd Ions

100%
Orlowski B., Osinniy V., Dziawa P., Pietrzyk M., Kowalski B., Taliashvili B., Story T., Johnson R.
Acta Physica Polonica A
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2008
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vol. 114
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issue 2
351-356
EN
The Fano resonance photoemission studies of Gd/(Pb, Gd)Te layers using synchrotron radiation were carried out and the electronic structure parameters like binding energies of Gd^{3+} 4f and 5p shells, resonance and antiresonance energies for Gd^{3+} were determined. The presence of Eu^{3+} ions was observed in the (Pb, Eu)Te and (Eu, Gd)Te layers grown by MBE technique. The comparison of data for (Pb, Gd)Te compound with corresponding data for (Eu, Gd)Te and (Pb, Eu)Te layers indicates that we are not able to distinct the Eu^{3+}4f and Gd^{3+}4f electrons contribution to the valence band photoemission spectra because of small content od Gd and similar binding energy values. The key parameters allowing to prove exactly the presence of either Eu^{3+} or Gd^{3+} are the resonance and antiresonance energies which are significantly different for these ions and equal to 143 eV/137 eV and 150 eV/142 eV, respectively.
4
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Influence of Atomic Sphere Radii on the Electron-Positron Momentum Density Calculated for SiC within the LMTO-ASA

80%
Rubaszek A.
Acta Physica Polonica A
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2006
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vol. 110
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issue 5
683-689
EN
The atomic sphere approximation consists in replacing the Wigner-Seitz polyhedron, containing individual atom, by the sphere of the same volume. In the case of several not equivalent atoms per primitive cell, e.g. for SiC, the radii of atomic spheres, centred at different atoms, are not uniquely determined and should be judiciously chosen. In the present work one studies the effect of choice of atomic sphere radii on the resulting electron band structure and momentum density as well as the electron-positron momentum density. Calculations were performed for SiC within the linear muffin-tin orbital atomic sphere approximation method.
5
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Effect of the Positron Distribution on the Electron-Positron Momentum Density Calculated for SiC

80%
Rubaszek A.
Acta Physica Polonica A
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2008
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vol. 113
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issue 5
1501-1506
EN
To interpret positron annihilation data in solids in terms of the electron momentum density, both the electron-positron interaction and positron distribution have to be considered explicitly. In the present work the influence of the shape of the positron wave function on the calculated electron-positron momentum density in elemental SiC is discussed. It is shown that the form of the positron distribution in the Wigner-Seitz cell has a considerable effect on the resulting annihilation characteristics. Calculations were performed for SiC of 3C diamond structure within the linear muffin-tin orbital-atomic spheres approximation method.
6
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Resonant Photoemission Study οf 4f Electrons on the Surface οf Semiconductors

80%
Orłowski B., Kowalski B., Pietrzyk M., Buczko R.
Acta Physica Polonica A
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2008
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vol. 114
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issue S
S-103-S-114
EN
The contribution of 4f electrons to the electronic structure of the semiconductor clean surface caused by the surface doping of it by rare-earth metal atoms (Eu, Sm) will be presented. The surface doping was performed by the controlled, sequential deposition of the rare-earth metal atoms on the clean surface in UHV conditions (Sm on GaN or CdTe) or by the doping of the layer volume of (EuGd)Te. After each deposition or surface treatment the synchrotron radiation was used to measure in situ the resonant photoemission spectra (the Fano type resonance) to study the contribution of 4f electrons of divalent and trivalent Sm and Eu ions to the valence band electronic structure of created sample. The first stages of the metal atoms deposition lead to the surface doping. Further metal atoms deposition leads to the growth of the metallic islands on the surface and causes the appearance of the sharp metallic Fermi edge in the energy distribution curves. Proper coverage and annealing of the sample surface with metal atoms leads to the diffusion of the metal atoms into the sample and results in an increase in the crystal doping and decrease in the metallic islands contribution to the measured spectra. As a result, the new electronic structure of the valence band can be created and investigated in situ.
7
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A Comparison of the Valence Band Structure of Bulk and Epitaxial GeTe-based Diluted Magnetic Semiconductors

80%
Pietrzyk M., Kowalski B., Orlowski B., Knoff W., Story T., Dobrowolski W., Slynko V., Slynko E., Johnson R.
Acta Physica Polonica A
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2010
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vol. 117
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issue 2
293-295
EN
In this work we present a comparison of the experimental results, which have been obtained by the resonant photoelectron spectroscopy for a set of selected diluted magnetic semiconductors based on GeTe, doped with manganese. The photoemission spectra are acquired for the photon energy range of 40-60 eV, corresponding to the Mn 3p → 3d resonances. The spectral features related to Mn 3d states are revealed in the emission from the valence band. The Mn 3d states contribution manifests itself in the whole valence band with a maximum at the binding energy of 3.8 eV.
8
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Photoemission Electronic Spectra οf CdTe/Pb_{0.95}Eu_{0.05}Te/CdTe

80%
Orlowski B., Dziawa P., Gas K., Reszka A., Mickievicius S., Thiess S., Drube W.
Acta Physica Polonica A
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2011
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vol. 120
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issue 5
960-963
EN
The synchrotron radiation was used to apply tunable high energy X-ray photoemission spectroscopy for investigation of electronic structure of semiconductor nanostructure CdTe/Pb_{0.95}Eu_{0.05}Te/CdTe/GaAs(001) top part. The Pb_{0.95}Eu_{0.05}Te (6 nm thick) was buried under thin (22 nm) top layer of CdTe transparent for part of electrons photoemitted from Pb_{0.95}Eu_{0.05}Te buried layer. The top layer of CdTe was sputtered by Ar ion bombardment for surface cleaning and for leaving the thickness of CdTe more transparent for photoelectrons emitted from buried layer. For these thickness of the top layer the photoemission energy distribution curves corresponding to the valence band and core levels electrons of the buried layer atoms were measured with application of synchrotron radiation of energy hν = 3510 eV. The measured spectra corresponding to the buried layer atoms were observed in the valence band region and in the high binding energy region for core levels of Pb 4f, Pb 3d. The valence band contribution and core levels Cd 4d and Cd 3d were obtained mainly from top cover layer. Measured Te 4d, Te 3d and Te 4d spectra possess contribution as well from top cover layer as from the buried layer. The amount of Eu atoms was to small to be reasonable detected and presented in the paper.
9
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Study of p-Layer Doping Density and Surface Band Bending on the Indium Tin Oxide/Hydrogenated Amorphous Silicon Heterojunction Solar Cells

80%
Rached D., Madani Yssad H.
Acta Physica Polonica A
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2015
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vol. 127
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issue 3
767-769
EN
A solar cell (indium tin oxide (ITO)/p-doped amorphous silicon (p-a-Si:H)/intrinsic polymorphous silicon (i-pm-Si:H)/n-doped crystalline silicon (n-c-Si)) simulation, focused on p-layer doping density NA and surface band bending E_{sbb} at the interface ITO/p-layer has been performed. Despite the deterioration of p-layer material quality with doping density, the reduced bulk recombination was found to compensate for the increased loss in the p-layer. An increase of p-layer doping density NA and contact barrier height φ_{b0} (variation of the surface band bending E_{sbb}) leads to an increase of the efficiency of heterojunction with intrinsic thin layer solar cells.
10
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Transverse Acoustoelectric Effect Applying in Surface Study of GaP:Te(111)

70%
Pustelny B., Pustelny T.
Acta Physica Polonica A
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2009
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vol. 116
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issue 3
383-384
EN
The possibility of using the transverse acoustoelectric phenomena in experimental investigations of near surface region in semiconductor crystals was discussed. The results of experimental investigations of GaP:Te(111) surfaces by means of the transverse acoustoelectric voltage were presented. Applying the transverse acoustoelectric voltage method, the lifetime τ of minority carrier in the near-surface region and the surface potential V_{s} in GaP:Te(111) surfaces after their different technological treatments were determined.
11
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Universality of the Empty-Lattice Approximation to Predict the Topology of Energy Spectra of High-Symmetry Crystals and Superlattices Based upon Them

70%
Sznajder M., Bercha D., Glukhov K., Slipukhina I.
Acta Physica Polonica A
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2006
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vol. 110
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issue 3
369-378
EN
O_h^7, T_d^2 and O_h^5 symmetry crystals were discussed to demonstrate universality of the empty-lattice approximation to obtain the topology and symmetry of the elementary energy bands creating the valence band of those crystals and to predict a localization of the maximum of valence electron density distribution in the unit cell. The elaborated concept of the elementary energy bands was applied to the (GaAs)_5/(AlAs)_5 superlattice and ordered solid solution Pb_{0.5}Sn_{0.5}S.
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