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1
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Ballistic Transport Phenomena in Nanostructures of Paraelectric Lead Telluride

100%
Grabecki G.
Acta Physica Polonica A
|
2007
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vol. 112
|
issue 2
127-139
EN
This is a review of our recent developments in the physics of lead telluride nanostructures. PbTe is a IV-VI narrow gap paraelectric semiconductor, characterized by the huge static dielectric constant ε >1000 at helium temperatures. We nanostructurized this material by means of e-beam lithography and wet chemical etching of modulation doped PbTe/Pb_{1-x}Eu_xTe quantum wells. Magnetoresistance measurements performed on the nano-structures revealed a number of magnetosize effects, confirming a ballistic motion of the carriers. The most important observation is that the conductance of narrow constrictions shows a precise zero-field quantization in 2e^2/h units, despite a significant amount of charged defects in the vicinity of the conducting channel. This unusual result is a consequence of a strong suppression of the Coulomb potential fluctuations in PbTe, an effect confirmed by numerical simulations. Furthermore, the orbital degeneracy of electron waveguide modes can be controlled by the width of PbTe/Pb_{1-x}Eu_xTe quantum wells, so that unusual sequences of plateau conductance can be observed. Finally, conductance measurements in a nonlinear regime allowed for an estimation of the energy spacing between the one-dimensional subbands.
2
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Optical Studies of HgCdMnTe Bicrystals

51%
Grabecki G., Wróbel J., Karczewski G.
Acta Physica Polonica A
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1991
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vol. 79
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issue 2-3
221-223
EN
We report preliminary results of optical measurements performed on Hg_{1-x-k}Cd_{x}Mn_{k}Te grain boundaries. Photovoltaic spectra and I-V characteristics under illumination exhibit metastable behavior, confirming our previous conclusions based on transport measurements under high hydrostatic pressure.
3
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Observation of Two-Dimensional Electron Gas in LPE-Grown GaInAs-InP Heterostructures

45%
Fronc K., Grabecki G., Wróbel J., Dietl T., Gajewska M.
Acta Physica Polonica A
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1991
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vol. 80
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issue 3
449-452
EN
A series of GaInAs/InP heterostructures was grown by liquid phase epitaxy. The heterostructures were characterized by magnetotransport measurements carried out down to 1.8 K and up 10 T. The results demonstrate the existence of the high-mobility two-dimensional electron gas in the narrow-gap GaInAs as well as the presence of residual conductance through the InP buffer layer.
4
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Megagauss Cyclotron Resonance and Quantum Hall Effect of 2D Electron Gas in HgCdMnTe

39%
Grabecki G., Takeyama S., Dietl T., Takamasu T., Shimamotο Y., Miura N.
Acta Physica Polonica A
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1995
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vol. 88
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issue 4
731-734
EN
Two-dimensional electron gas adjacent to a grain boundary in bicrystal of narrow-gap semiconductor p- Hg_{0.79}Cd_{0.19}Mn_{0.02}Te has been studied under ultra strong impulse magnetic fields (up to 140 T). Both cyclotron resonance and quantum Hall effect are measured for the same samples. The values of the resonance fields point to strong nonparabolicity. A broadening of the line is interpreted in terms of an intersubband mixing that occurs for the upper Landau level. A steep increase in the linewidth in the field range 20-30 T, which coincides with a strong decrease in the Hall resistance is assigned to the field-induced metal-insulator transition in our system.
5
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Exciton Magneto-Optical Study on Single Quantum Wells, Cd_{1-x}Zn_{x}Te/Cd_{1-x'-y}Zn_{x}'Mn_{y}Te

39%
Takeyama S., Grabecki G., Adachi S., Takagi Y., Wojtowicz T., Karczewski G., Kossut J.
Acta Physica Polonica A
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1995
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vol. 88
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issue 5
945-948
EN
Four-single quantum wells composed of the ternary non-magnetic compounds Cd_{0.93}Zn_{0.07}Te (well width = 13, 19, 40, 90 Å), separated by the quaternary magnetic-compound Cd_{0.48}Zn_{0.04}Mn_{0.48}Te on (100)GaAs substrate were grown by MBE, and exhibited clear and distinctive photoluminescence lines corresponding to each quantum well. Double luminescence peaks with closely spaced within one well were observed from 90 Å and 40 Å quantum wells. Temperature and magnetic-field study revealed characteristic luminescence features associated with a bound exciton near the interface rather than with one monolayer fluctuation.
6
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Precision of the Hall Quantization in Naturally Occurring Two-Dimensional System - HgCdMnTe Bicrystals

39%
Grabecki G., Wittlin A., Dietl T., Teunissen P., Wiegers S., Perenboom J.
Acta Physica Polonica A
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1992
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vol. 82
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issue 5
733-736
EN
New magnetoresistance measurements on naturally occurring inversion layers adjacent to grain boundaries in narrow gap diluted magnetic semiconductor HgCdMnTe (Eg ≤ 200 meV) have been performed. The magnetic fields up to 20 T simultaneously with millikelvine temperatures have been applied. Possible experimental factors affecting the quantum Hall effect in our system are discussed in detail.
7
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Magnetoresistance of Si/Nb/Si Trilayers

33%
Zaytseva I., Cieplak M., Abal'oshev A., Dluzewski P., Grabecki G., Plesiewicz W., Zhu L., Chien C.
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issue 2
406-408
EN
We study the superconductor-insulator transition in Si/Nb/Si trilayers, in which the thickness of Si is fixed at 10 nm, and the nominal thickness of Nb changes in the range between d = 20 nm down to d = 0.3 nm. The transmission electron microscopy indicates the formation of the mixed Nb-Si layer for small d. Both the thickness-induced, and the magnetic-field induced superconductor-insulator transition is observed. The crossing point of the isotherms at the critical field B_{c} decreases with decreasing d, and it is T-independent at temperatures below 300 mK. At larger fields the weak peak in magnetoresistance appears in some of the films.
8
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Effects of Ballistic Transport in Wires of n-PbTe

33%
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?

33%
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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Mesoscopic Phenomena in Microstructures of IV-VI Epilayers

33%
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
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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.
11
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Conductance Fluctuations in Microstructures of HgCdMnTe Bicrystals

33%
Grabecki G., Lenard A., Plesiewicz W., Jaroszyński J., Cieplak M., Skośkiewicz T., Dietl T., Kamińska E., Piotrowska A., Bulka B.
Acta Physica Polonica A
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1991
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vol. 80
|
issue 2
307-310
EN
Microscopic four-contact probes to semimagnetic HgCdMnTe grain-boundary inversion layers have been photolithographically patterned. Magnetoresistance measurements performed on these samples revealed aperiodic conductance fluctuations of the magnitude of the order of e^{2}/h. Quantitative analysis of both fluctuation amplitude and their mean period indicate that we have approached the mesoscopic regime in our system. This opens new possibilities in studies of spin-subsystem dynamics in semimagnetic semiconductors.
12
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Second Harmonic Generation in Spin-Glass Microstructures and Fabrication of Microstructures in IV-VI Epilayers

27%
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
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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
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Electrical and Structural Properties of Ohmic Contacts to n-Type and High Resistivity CdTe

27%
Kamińska E., Piotrowska A., Guziewicz M., Gierlotka S., Papis E., Łusakowski J., Szadkowski K., Kwiatkowski S., Dietl T., Grabecki G., Jaroszyński J., Karczewski G., Zakrzewski A. K.
Acta Physica Polonica A
|
1995
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vol. 87
|
issue 2
411-414
EN
The interaction between CdTe and In during the formation of an ohmic contact has been investigated. Emphasis is placed on the study of the effect of thermally induced sublimation of cadmium on electrical properties of con­tacts. Presented results prove the effectiveness of cap annealing and rapid thermal processing in fabrication of improved ohmic contacts with limited Cd losses during the contacting procedure.
14
Content available remote

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

27%
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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