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1
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s-p-d-f Exchange Interactions in Mn and Eu Based IV-VI Semimagnetic Semiconductors

100%
Dietl T., Bauer G.
Acta Physica Polonica A
|
1992
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vol. 82
|
issue 5
729-732
EN
We evaluated exchange integrals which describe the spin dependent coupling between effective mass electrons and localized spins in the IV-VI semi-magnetic semiconductors taking into account contributions from the direct Coulomb exchange as well as from the hybridization between band states and magnetic shells. The obtained constants compare favorably with the experimental values for both the Mn- and the Eu-based compounds. We also discuss some peculiarities of IV-VI semimagnetic semiconductors, which may render the virtual-crystal approximation invalid.
2
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Scattering Theory of the Johnson Spin Transistor

81%
Geux L., Brataas A., Bauer G.
Acta Physica Polonica A
|
2000
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vol. 97
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issue 1
119-128
EN
We discuss a simple, semiclassical scattering theory for spin-dependent transport in a many-terminal formulation, with special attention to the four terminal device of Johnson referred to as spin transistor.
3
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High Resolution X-ray Reciprocal Space Mapping

81%
Bauer G., Li J., Holy V.
Acta Physica Polonica A
|
1996
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vol. 89
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issue 2
115-127
EN
A survey will be given on recent advances in the investigation of semiconductor epilayers, heterostructures and superlattices using reciprocal space mapping techniques based on triple-axis diffractometry. It is shown that X-ray reciprocal space mapping yields quantitative information on strain, strain relaxation, as well as composition in such structures. These data are obtained from analyses of the isointensity contours of scattered X-ray intensity around reciprocal lattice points. Further analysis of the diffuse scattering yields also information on defect distribution in the epilayers.
4
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Investigation of Morphology and Chemical Composition of Self-Organized Semiconductor Quantum Dots and Wires by X-Ray Scattering

71%
Holý V., Meduňa M., Stangl J., Roch T., Bauer G.
Acta Physica Polonica A
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2002
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vol. 102
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issue 1
7-19
EN
X-ray scattering methods suitable for the investigation of the morphology and chemical composition of self-organized quantum dots and quantum wires are reviewed. Their application is demonstrated in experimental examples showing that a combination of small angle X-ray scattering with high-resolution X-ray diffraction can reveal both the shape and the chemical composition of the self-organized objects.
5
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Strain Relaxation Induced Red Shift of Photoluminescence of CdZnSe/ZnSe Quantum Wires

71%
Straub H., Brunthaler G., Faschinger W., Bauer G., Vieu C.
Acta Physica Polonica A
|
1996
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vol. 90
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issue 5
1085-1089
EN
Wire patterns (80-1000 nm) of molecular beam epitaxy grown Cd_{0.2}Zn_{0.8}Se/ZnSe quantum well were fabricated by a CH_{4}/H_{2} reactive ion etching technique. Photoluminescence emission shows with decreasing lateral size a broadening of line shape and a spectral red shift. Calculations for the change of the band gap due to strain relaxation show that this shift of the photoluminescence emission for narrow Cd_{0.2}Zn_{0.8}Se/ZnSe structures (lattice mismatch of 1.34%) can be explained by a partial elastic strain relaxation of the biaxially compressively strained Cd_{0.2}Zn_{0.8}Se quantum well after the patterning process.
6
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Weak Localization and Electron-Electron Interaction in Si/SiGe Quantum Wells

62%
Prinz A., Stőger G., Brunthaler G., Bauer G., Ismail K., Meyerson B. S.
Acta Physica Polonica A
|
1995
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vol. 88
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issue 5
873-876
EN
A negative magnetoresistance is observed in Si/SiGe modulation doped heterostructures which is attributed to the single particle quantum interference (weak localization) effect. From analysis of the experimental data the electron phase coherence time τ_{ϕ} is extracted to follow a (aT + bT^{2} )^{-1} dependence. The evaluated prefactor α = 0.25 is below the theoretical limit of 0.5, but agrees with observations in Si and GaAs/AlGaAs heterostructures.
7
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High Resolution X-Ray Diffraction Investigations of Si/SiGe Quantum Well Structures and Si/Ge Short-Period Superlattices

52%
Bauer G., Koppensteiner E., Hamberger P., Nützel J., Abstreiter G., Kibbel H., Presting H., Kasper E.
Acta Physica Polonica A
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1993
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vol. 84
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issue 3
475-489
EN
Double crystal and triple axis X-ray diffractometry was used to characterize the structural properties of Si/Si_{1-x}Ge_{x} multiquantum well samples grown pseudomorphically on Si(001) substrates, as well as of short-period Si_{9}Ge_{6} superlattices grown by molecular beam epitaxy on rather thick step-graded Si_{1-x}Ge_{x} (0 < x < 0.4, 650 nm thick) buffers followed by 550 nm Si_{0.6} Ge_{0.4} layers. Reciprocal space maps around the (004) and (224) reciprocal lattice points yield direct information on the strain status of the layers in the heterostructure systems and in particular on the amount of strain relaxation.
8
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Effects of Ballistic Transport in Wires of n-PbTe

52%
Grabecki G., Wróbel J., Dietl T., Papis E., Kamińska E., Piotrowska A., Ueta Y., Sprinholtz G., Bauer G.
Acta Physica Polonica A
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1997
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vol. 92
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issue 4
789-792
EN
We present results of magnetotransport studies on quantum wires of submicron PbTe epilayers, fabricated by means of electron beam lithography and dry etching. When the wire width is reduced down to 1 μm, the transition from diffusive to ballistic regime is observed. Effects associated with collimation and boundary scattering are found in the Hall, longitudinal, and van der Pauw magnetoresistance for wires and junctions in the shape of a cross.
9
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Conductance Fluctuations in PbSe: Manifestation of Ballistic Transport in Macroscale?

52%
Grabecki G., Takeyama S., Adachi S., Takagi Y., Dietl T., Kamińska E., Piotrowska A., Papis E., Frank N., Bauer G.
Acta Physica Polonica A
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1995
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vol. 88
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issue 4
727-730
EN
Precise magnetoresistance measurements on microstructures of photolithographically patterned PbSe epilayers have been performed in the mag­netic field range up to 17 Τ. Unusually large, reproducible magnetoconductance fluctuations have been observed. The fluctuation amplitude decreases exponentially with the magnetic field. A correlation magnetic field of the fluctuations corresponds to the Aharonov-Bohm effect which involves elec­tron trajectories much smaller than the electron mean free path. This points strongly to the ballistic, not diffusive, origin of the observed phenomenon.
10
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Electron Localization in Sb-Doped Si/SiGe Superlattices

52%
Dietl T., Jaroszyński J., Sawicki M., Głód P., Wróbel J., Stöger G., Brunthaler G., Bauer G., Schäffler F.
Acta Physica Polonica A
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1995
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vol. 88
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issue 4
699-702
EN
Millikelvin studies of in-plane magnetoconductance in short period Si/Ge:Sb superlattices have been carried out in order to examine the effect of anisotropy on quantum localization. The field-induced metal-to-insulator transition has been observed, indicating the existence of extended states. This suggests that despite anisotropy as large as D_{∥}/D_{⊥} ≈ 10^{3} the system behaves as 3D in respect of localization by disorder.
11
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Mesoscopic Phenomena in Microstructures of IV-VI Epilayers

52%
Grabecki G., Dietl T., Plesiewicz W., Lenard A., Skośkiewicz T., Kamińska E., Piotrowska A., Papis E., Frank N., Bauer G.
Acta Physica Polonica A
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1995
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vol. 87
|
issue 2
551-554
EN
Magnetoresistance measurements of photolithographically patterned PbSe and Pb-{1-y}Mn_{x}Se microstructures were performed. Reproducible mag­netoconductance fluctuations with the amplitude increasing with decreasing temperature were observed. Unexpectedly, these fluctuations contain a com­ponent periodic in the magnetic field, and their magnitude is greater than that expected from the current theory of the universal conductance fluctua­tions. Possible explanations are discussed.
12
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Second Harmonic Generation in Spin-Glass Microstructures and Fabrication of Microstructures in IV-VI Epilayers

42%
Grabecki G., Dietl T., Cieplak M., Plesiewicz W., Lenard A., Skośkiewicz T., Kamińska E., Piotrowska A., Żarecka R., Springholz G., Bauer G.
Acta Physica Polonica A
|
1993
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vol. 84
|
issue 4
781-784
EN
We studied magnetoconductance of two different mesoscopic systems: microregions containing two-dimensional electron gas adjacent to a grain-boundary plane in bicrystals of Hg_{0.79}Cd_{0.19}Mn_{0.02}Te and photolithographically patterned microstructures of Pb_{1-x}Mn_{x}Se. In both systems universal conductance fluctuations and generation of the second-harmonic voltage were observed at T ≤ 1 K. Moreover, in the former system the second harmonic signal exhibited distinct rise when the sample was cooled below the spin-glass freezing temperature (100 mK).
13
Content available remote

Conductance Anomalies in Strained Quantum Wires: the Case of PbSe and PbTe

42%
Grabecki G., Wróbel J., Dietl T., Sawicki M., Skośkiewicz T., Papis E., Kamińska E., Piotrowska A., Frank N., Ueta Y., Sprinholtz G., Bauer G.
|
EN
We show that conducting edge channels are formed in free standing wires of PbSe/BaF_{2} and PbTe/BaF_{2} as temperature is lowered. The effect results from spatially inhomogeneous strain caused by a difference between the thermal expansion coefficients of the epilayer and the substrate. The presence of the edge channels can explain anomalous mesoscopic effects observed previously in these wires.
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