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  1. 51 Acta Physica Polonica A

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  1. 51 Dobrowolski W.

  2. 17 Story T.

  3. 14 Arciszewska M.

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1
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HgSe Based Mixed Crystals Doped with Fe Resonant Donors

100%
Dobrowolski W.
Acta Physica Polonica A
|
1996
|
vol. 89
|
issue 1
3-36
EN
The article reviews the physical properties of semimagnetic semiconductors of the type Hg_{1-x-y}Fe_{x}A^{II}_{y}Se_{1-z}B^{VI}_{z} and Hg_{1-x-y}Fe_{x}Mn_{y}Se. Optical, magnetooptical, transport and magnetotransport experiments showed that in Hg_{1-x}Fe_{x}Se substitutional iron forms a resonant donor state whose energy is superimposed on the conduction band continuum. Resulting anomalous properties of electron scattering rate, i.e. strong enhancement of electron mobility (or drop of Dingle temperature), which occur in Hg_{1-x}Fe_{x}Se at low temperatures in a certain Fe concentration range, are described. Next, theoretical models describing this anomalous reduction of the scattering rate are discussed. The description of thermomagnetic, optical, magnetooptical and magnetic properties of Hg_{1-x}Fe_{x}Se, with emphasis on features originating from the peculiar iron level position in the band structure of Hg_{1-x}Fe_{x}Se, conclude the first part of the present paper. In the second part the physical properties of the semiconducting alloys Hg_{1-x}Mn_{x}Se:Fe, Hg_{1-v}Cd_{v}Se:Fe, Hg_{1-x}Zn_{x}Se:Fe, HgSe_{1-x}Te_{x}:Fe and HgSe_{1-x}S_{x}:Fe are described. In particular, the dependence of the position of the Fe resonant donor state in the band structure on the crystal composition is discussed. The values of predicted Γ_{6} and Γ_{8} band offsets between HgSe and CdSe, HgTe, MnSe and ZnSe are given. The considerable attention is paid to the discussion of the mechanism limiting the electron mobility in the mixed alloys. Finally, topics which have not been explicitly covered in this review are mentioned and open problems are discussed.
2
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Improvement of Electrical Properties of Hg_{1-x}Zn_{x}Se upon Doping with Fe

52%
Dobrowolski W., Grodzicka E., Kossut J., Witkowska B.
|
EN
Results of measurements of electron concentration and mobility in mixed crystals of Hg_{1-x}Zn_{x}Se (0 ≤ x ≤ 0.07) doped with resonant Fe donors (0 ≤ n_{Fe} ≤ 5 × 10^{19} cm^{-3}) at liquid helium temperatures are presented. The data show that there is a considerable improvement of the electrical properties of the material when Fe impurities are present. The analysis of the mobility in terms of the scattering from ionized centers (accounting for possible spatial correlation of impurity charges) and the alloy scattering is in agreement with the measured data.
3
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Interaction Between Magnetic Layers in Structures with Narrow-Gap IV-VI Semiconductors

52%
Dugaev V., Litvinov V., Dobrowolski W., Story T.
Acta Physica Polonica A
|
2000
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vol. 97
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issue 3
455-458
EN
The results of calculation of the indirect exchange interaction between magnetic layers are presented for the case of a structure with narrow-gap semiconducting IV-VI quantum well. The main mechanism is a magnetic polarization of the size-quantized electrons and holes inside the well. This type of interaction is suggested for the explanation of recent experiments on EuS/PbS structures.
4
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Resonant Tunnelling in Double-Barrier Heterostructures with an Accumulation Layer

46%
Wosiński T., Figielski T., Mąkosa A., Wrotek S., Dobrowolski W.
Acta Physica Polonica A
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1998
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vol. 94
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issue 3
617-621
EN
Two modes of electron gas injection in resonant tunnelling through GaAs/AlGaAs double-barrier heterostructures were revealed while studying their current-voltage characteristics. Examining peculiarities of the characteristics within the temperature range 4-350 K and under a high magnetic field, we were able to distinguish the contribution to resonant tunnelling of ballistic electrons injected from a three-dimensional electron gas in the emitter contact and that of electrons injected from a two-dimensional electron gas in the accumulation layer formed near the emitter barrier.
5
Content available remote

Magnetooptical Properties of Pb_{1-x}Mn_{x}Se p-n Junctions

46%
Khoi L., Karczewski G., Dobrowolski W., Kossut J., Gałązka R.
Acta Physica Polonica A
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1991
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vol. 80
|
issue 3
445-448
EN
The first experimental evidence of the magnetic quantum oscillation in the photovoltaic effect of Pb_{1-x}Mn_{x}Se p-n junctions is reported. The p-n junctions were obtained in Pb_{1-x}MnxSe crystals with manganese content, 0 ≤ x ≤ 0.08 by introducing Cd donors by diffusion. Measurements were per formed between 5-85 K and in the presence of the magnetic field 0-7 T in the Faraday and Voigt configurations of the incident infrared radiation of various photon energies in the vicinity of the energy gap of a Pb_{1-x}Mn_{x}Se. Strong oscillatory behavior of the photovoltage was observed as a function of the magnetic field intensity at a constant wavelength of the incident light. Using the model of Adler of the energy band structure modified by the exchange terms, and after identification of the initial and final states of the transitions, we derive the band parameters of the Pb_{1-x}Mn_{x}Se crystals.
6
Content available remote

Electron Paramagnetic Resonance of Cr in PbTe

46%
Story T., Wilamowski Z., Grodzicka E., Witkowska B., Dobrowolski W.
Acta Physica Polonica A
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1993
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vol. 84
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issue 4
773-775
EN
We present the results of the low temperature electron paramagnetic resonance (EPR) and transport investigations of the crystals of Pb_{1-x}Cr_{x}Te (x ≤ 0.01). The samples with chromium concentrations x ≥ 0.0015 are all n-type. For these samples we observe the single EPR line with the g-factor decreasing from g = 1.97 till g = 1.93 with increasing carrier concentration. This resonance can be attributed to electrically and magnetically active Cr^{3+} ions. The crystals with Cr concentration x ≤ 0.0015 may be both n- and p-type. The EPR spectrum of these samples consists of two lines: the one discussed above and the other one with g = 1.99 observed only for samples with electron concentration n ≤ 10^{18} cm^{-3}.
7
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Transport and Magnetic Properties of PbTe:Cr and PbSnTe:Cr

46%
Story T., Grodzicka E., Witkowska B., Górecka J., Dobrowolski W.
Acta Physica Polonica A
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1992
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vol. 82
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issue 5
879-881
EN
We present the results of the experimental studies of the low temperature transport and magnetic properties of PbTe, Pb_{1-x}Sn_{x}Te (x ≤ 0.3) and SnTe crystals doped with 0.5 at.% of chromium. Cr was found to be a resonant donor in PbTe and PbSnTe. Magnetic susceptibility measurements revealed that PbTe:Cr and Pb_{1-x}Sn_{x}Te:Cr (x ≤ 0.2) are Curie paramagnets whereas SnTe:Cr exhibits van Vleck paramagnetism.
8
Content available remote

Effect of Magnetic Field on Fine Structure of Tunnel Current in Double-Barrier Resonant-Tunneling Devices

46%
Belyaev A. E., Vitusevich S. A., Glavin B. A., Mąkosa A., Dobrowolski W.
Acta Physica Polonica A
|
1995
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vol. 88
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issue 4
675-678
EN
An effect of magnetic field on a fine oscillatory structure revealed in the resonant current flowing through double-barrier resonant-tunneling devices is examined. It is found that the observed variation of the fine structure in a magnetic field parallel to the current direction differs considerably from that appearing in tunnel current flowing through single-barrier structures. Experimental results are explained in terms of the quantum interference effect arising in structures having wide spacer layers.
9
Content available remote

Magnetic Properties of "As-Prepared" and Chemically Modified Multiwalled Carbon Nanotubes

46%
Kuryliszyn-Kudelska I., Małolepszy A., Mazurkiewicz M., Stobinski L., Dobrowolski W.
Acta Physica Polonica A
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2011
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vol. 119
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issue 5
597-599
EN
In this work we have studied the structural and magnetic properties of "as-prepared" multiwalled carbon nanotubes, synthesized by the chemical vapor deposition method, and chemically modified multiwalled carbon nanotubes. Transmission electron microscopy was used to show multiwalled carbon nanotubes structure. The results of systematic magnetic property measurements on multiwalled carbon nanotubes are presented. The static and dynamic magnetic responses, such as the temperature dependence of the linear AC susceptibility and DC magnetization up to 9 T were studied. We have observed significant changes in magnetic AC susceptibility and magnetization for "as-prepared" and chemically modified multiwalled carbon nanotubes samples.
10
Content available remote

Peculiarities of Electron Transport in PbTe:Cr due to Presence of Resonant Impurity State

46%
Grodzicka E., Dobrowolski W., Kossut J., Story T., Witkowska B.
Acta Physica Polonica A
|
1993
|
vol. 84
|
issue 3
599-603
EN
The results of transport investigation of Pb_{1-x}Cr_{x}Te (x ≤ 0.009) in temperature range 3.5-300 K are presented. The obtained electron concentration and electron mobility vs. temperature and Cr concentration data are interpreted and discussed within the model assuming that Cr in PbTe forms a donor state resonant with the conduction band.
11
Content available remote

Aharonov-Bohm Effect at Misfit Dislocations in GaAsSb/GaAs Heterostructures

46%
Figielski T., Wosiński T., Mąkosa A., Dobrowolski W., Raczyńska J.
Acta Physica Polonica A
|
1996
|
vol. 90
|
issue 4
773-776
EN
We examined the current flowing through p^{+}-n junction of the lattice mismatched GaAs_{1-x}Sb_{x}/GaAs heterostructure in a transverse magnetic field at 1.8 K. We have found the appearance of current oscillations, periodic as a function of the magnetic field, that are due to the Aharonov-Bohm effect of holes passed around charged dislocations.
12
Content available remote

Anomalous Hall Effect in IV-VI Semiconductors

46%
Dyrdał A., Dugaev V., Barnaś J., Brodowska B., Dobrowolski W.
Acta Physica Polonica A
|
2009
|
vol. 115
|
issue 1
287-289
EN
We consider theoretically the topological contribution to the anomalous Hall effect in narrow-gap IV-VI magnetic semiconductors in which the relativistic terms are relatively large and determine both the non-parabolicity of the energy spectrum and strong spin-orbit interaction. We use the relativistic Dirac model and linear response theory to calculate this contribution. Experimental data on the anomalous Hall effect in these compounds are also presented and discussed.
13
Content available remote

Self-Induced Persistent Photoconductivity in ZnTe-Cd_{1-x}Mn_{x}Te_{1-y}Se_{y} Heterojunctions

46%
Van Khoi L., Dobrowolski W., Zakrzewski A., Dobaczewski L., Gałązka R.
|
EN
At temperatures lower than 200 K the photomemory effect has been observed in ZnTe-Cd_{1-x}Mn_{x}Te_{1-y}Se_{y} heterojunctions. The persistent photoconductivity can be achieved either by illumination from an external light source or by a self-absorption of the electroluminescence radiation when a voltage of about 10 V for a few seconds is applied to the diode. Current-voltage characteristics are of the form I~ V^{m}. The capacitance and electroluminescence measurements show that the photomemory effect in ZnTe-Cd_{1-x}Mn_{x} Te_{1-y}Se_{y} heterojunctions can be caused by the bistable nature of the In dopant in the Cd_{1-x}Mn_{x}Te_{1-y}Se_{y} substrate. In the high resistivity interface layer and the substrate material indium forms centers similar to DX-like centers in Zn_{x}Cd_{1-x}Te and Cd_{1-x}Mn_{x}Te.
14
Content available remote

Magnetic Properties of EuS/PbS Semiconducting Structures

40%
Stachow-Wójcik A., Twardowski A., Story T., Dobrowolski W., Grodzicka E., Sipatow A.
Acta Physica Polonica A
|
1997
|
vol. 92
|
issue 5
985-988
EN
We report results of magnetization study of EuS/PbS superstructures with different thicknesses of magnetic and nonmagnetic layers. Reduction of ferromagnetic phase transition temperature was found with decreasing EuS thickness. Reasonable description of this effect is obtained within the model based on the mean field approximation.
15
Content available remote

Pressure Study of Charged Donor Ordering in HgSe Doped with Iron and Gallium

40%
Skierbiszewski C., Suski T., Kossut J., Wilamowski Z., Dobrowolski W., Witkowska B.
Acta Physica Polonica A
|
1991
|
vol. 80
|
issue 3
401-404
EN
Transport experiments (Hall effect and conductivity) under hydrostatic pressure up to 1 GPa at liquid helium temperatures on HgSe: Fe, Ga (N_{Fe} = 2 x 10^{19} cm^{-3}; 0 ≤ N_{Ga} ≤ 10^{19} cm^{-3}) were performed. The results show that the gallium co-doping of HgSe:Fe decreases the degree of spatial correlations between charged impurities. Under the hydrostatic pressure, used as a tool for changing the ratio of the charged to neutral impurities, this effect is even more pronounced. A qualitative agreement between the calculation within the short-range correlation model and our experimental data is achieved.
16
Content available remote

Preparation and Luminescent Properties of ZnTe-Cd_{1-x}Mn_{x}Te_{1-y}Se_{y} Heterojunction

40%
Le K., Dobrowolski W., Witkowska B., Mycielski A., Galązka R., Nguyen K.
Acta Physica Polonica A
|
1995
|
vol. 87
|
issue 2
325-328
EN
ZnTe-Cd_{1-x}Mn_{x}Te_{1-y}Se_{y} heterojunctions were prepared by vapor-transport epitaxy of ZnTe on In-doped Cd_{1-x}Mn_{x}Te_{1-y}Se_{y} (x = 0.05, y = 0.03) single crystalline substrate in vacuum. At temperatures lower than 120 K the infrared and red electroluminescence were observed from the ZnTe-Cd_{1-x}Mn_{x}Te_{1-y}Se_{y} diode with forward current density in the range 0.003-4.0 A/cm^{2}.
17
Content available remote

Structural and Electrical Properties of SiC Grown by PVT Method in the Presence of the Cerium Vapor

40%
Avdonin A., Racka K., Tymicki E., Grasza K., Jakieła R., Pisarek M., Dobrowolski W.
Acta Physica Polonica A
|
2013
|
vol. 124
|
issue 5
761-764
EN
The results of investigation of structural and electrical properties of bulk SiC crystals, which were grown by physical vapor transport method with different Ce impurity content added to the SiC source material, are presented. The gradual dosage of cerium from the SiC source and continuous presence of the cerium vapor over the SiC crystallization fronts during the crystal growth processes are confirmed. The cerium influences the overall concentration of structural defects. The increase of the concentration of both, donors and acceptors, and appearance of new shallow donors (15-32 meV) in 4H-SiC crystals are observed.
18
Content available remote

PbSe:Cr - New Resonant Donor System

40%
Story T., Wilamowski Ż., Grodzicka E., Dobrowolski W., Witkowska B., Voiron J.
Acta Physica Polonica A
|
1995
|
vol. 87
|
issue 1
229-232
EN
Hall effect, conductivity, electron paramagnetic resonance and magneti­zation of Pb_{1-x}Cr_{x}Se (x ≤ 0.01) crystals were measured as a function of Cr content and electron concentration. The experimental results suggest that Cr in PbSe creates a resonant donor state with the energy of about 125 meV above the bottom of the conduction band.
19
Content available remote

Synthesis by Wet Chemical Method and Characterization of Nanocrystalline ZnO Doped with Fe_2O_3

40%
Narkiewicz U., Sibera D., Kuryliszyn-Kudelska I., Kilański L., Dobrowolski W., Romčević N.
Acta Physica Polonica A
|
2008
|
vol. 113
|
issue 6
1695-1700
EN
Nanocrystalline samples of ZnO doped with Fe_2O_3 were synthetized by wet chemical method. The series of ZnO nanosized samples in the wide range of Fe_2O_3 concentration (from 5 wt.% to 95 wt.%) was prepared by precipitation from nitrate solutions using ammonia. The phase composition of the samples was determined using X-ray diffraction measurements. The phases of hexagonal ZnO, and/or rhombohedric Fe_2O_3, and/or ZnFe_2O_4 were identified. The mean crystalline size of nanocrystals, determined with the use of Scherrer's formula, varied from 8 to 52 nm. The preliminary micro-Raman spectroscopy measurements were performed. The observed features are typical of Fe doped ZnO nanoparticles. The magnetic measurements revealed the presence of different types of magnetic behavior. For samples with high Fe_2O_3 contents (above 70 wt.%) the ferromagnetic ordering was observed at room temperature. For samples with lower Fe_2O_3 contents we observed the phenomenon of superparamagnetism above the blocking temperature.
20
Content available remote

Magnetically Controlled Interference of Ballistic Electrons Tunnelled throughout the Double-Barrier Resonator

40%
Figielski T., Wosiński T., Mąkosa A., Dobrowolski W., Vitusevich S., Belyaev A.
Acta Physica Polonica A
|
1996
|
vol. 90
|
issue 4
781-784
EN
An effect of magnetic field normal to the tunnel current on the amplitude and phase of the fine oscillatory structure, discovered in the resonance current-voltage curve in double-barrier AlAs/GaAs heterostructures, has been examined. All the obtained results are consistently explained in terms of the interference of ballistic electrons, escaped from the quantum well, in the collector part of the structure.
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