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1
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Raman Spectroscopy of Cubic HgS:Fe

100%
Szuszkiewicz W., Witkowska B., Jouanne M.
Acta Physica Polonica A
|
1995
|
vol. 87
|
issue 2
415-418
EN
From the Raman spectra performed at temperatures from 10 K to 295 K for Hg_{1-x}Fe_{x}S crystals containing up to a few percent of iron the phonon energies for selected high-symmetry points of the Brillouin zone have been determined. A very high ionicity of these mixed crystals has been found. The TO phonon frequency value for β-HgS at Γ point, equal to about 177 cm^{-1}, suggested previously in the literature, has been confirmed.
2
Content available remote

Co^{2+} Centres in ZnTe Crystals Heavily Doped with Cobalt

100%
Zaręba A., Szadkowski A., Mycielski A., Witkowska B.
Acta Physica Polonica A
|
1995
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vol. 87
|
issue 2
453-456
EN
Co^{2+} centre in ZnTe has been proved to be an acceptor, contrary to the previous assignment, but in agreement with the general trend in the behaviour of the transition metal impurities in the II-VI compounds. The threshold of the Co^{2+} + hν → Co^{+1} + h transition has been found in the spectrum of photoconductivity at about 1.4 eV, close to the value already reported.
3
Content available remote

Bound Exciton Luminescence in Phosphorus Doped Cd_{1-x}Mn_{x}Te Crystals

100%
Van Khoi L., Gałązka R., Witkowska B., The Khoi N.
Acta Physica Polonica A
|
1998
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vol. 94
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issue 3
392-396
EN
Measurement of photoluminescence as a function of temperature and of magnetic field in p-type phosphorus doped Cd_{1-x}Mn_{x}Te is reported. From the conduction band-acceptor level transition, the ionization energy of P-acceptors is obtained to be 54ą1 meV. The photoluminescence spectrum in the band edge region exhibits three maxima connected with the recombination of excitons bound to neutral acceptors (A^{0}, X), excitons bound to neutral donors (D^{0},X), and free excitons (X) at energies E_{(A^{0},X)}=1.606, E_{(D^{0},X)}=1.610, and E_{X}=1.614 eV, respectively. At T=1.4 K a strong increase in PL intensity of (A^{0}, X) line 8-fold as a function of magnetic field is found and shown to originate from the magnetic field-induced lowering of the acceptor binding energy and increase in the hole effective volume.
4
Content available remote

Improvement of Electrical Properties of Hg_{1-x}Zn_{x}Se upon Doping with Fe

100%
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.
5
Content available remote

Photovoltaic Effect on PbTe p-n Junction in the Presence of Magnetic Field

88%
Le K., Grodzicka E., Witkowska B., Story T., Gałązka R.
Acta Physica Polonica A
|
1993
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vol. 84
|
issue 4
721-724
EN
Photovoltaic spectra of PbTe p-n junction have been measured in the infrared spectral region in the temperature range of 8-260 K. The p-n junctions have been formed by cadmium diffusion into the p-type PbTe crystals. From the positions of the photovoltaic maxima the energy gap of the diode material has been determined. In the presence of a magnetic field up to 7 T, a pronounced oscillatory behavior of the photovoltage was observed in the Faraday and Voigt configurations. Experiments were performed as a function of the magnetic field intensity at a constant wavelength of the incident light. The energy of the interband magnetooptical transitions between the Landau levels in PbTe was determined and compared with the theoretical model of Adler, describing the energy band structure for the IV-VI compounds.
6
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Fe 3d Contribution to the Valence Band of Cubic Hg_{1-x}Fe_{x}S - Resonant Photoemission Study

88%
Kowalski B. J., Orłowski B. A., Szuszkiewicz W., Witkowska B., Johnson R. L.
Acta Physica Polonica A
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1995
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vol. 88
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issue 4
791-794
EN
Resonant photoemission spectra of cubic Ηg_{0.94}Fe_{0.06}S were measured for photon energies near to the energy of intra atomic Fe 3p^{6}3d^{6} → 3p^{5}3d^{7} transition. The difference between the spectra taken at resonance and an­tiresonance is presented as a measure of the energy distribution of Fe 3d derived states. The results obtained show that Fe 3d states contribute to the whole valence band with a distinct structure appearing at the band edge.
7
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Electron Scattering and the Band Structure of Mixed Crystals Hg_{1-x}Fe_{x}Se

88%
Skierbiszewski C., Wilamowski Z., Suski T., Kossut J., Witkowska B.
Acta Physica Polonica A
|
1992
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vol. 82
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issue 5
809-812
EN
In this paper the dependence of the band structure and the electron scattering mechanisms on the molar fraction x are studied in Hg_{1-x}Fe_{x}Se. The crossover from the zero-gap band to the open band-gap configuration at x ≈ 0.08 is predicted. We explain the drop of the electron mobility for x > 0.002 by the alloy scattering mechanism.
8
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Electron Paramagnetic Resonance of Cr in PbTe

88%
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
|
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}.
9
Content available remote

Transport and Magnetic Properties of PbTe:Cr and PbSnTe:Cr

88%
Story T., Grodzicka E., Witkowska B., Górecka J., Dobrowolski W.
Acta Physica Polonica A
|
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.
10
Content available remote

The Dynamic Dielectric Function "Anomaly" for HgSe:Ga and HgSe:Fe

88%
Szuszkiewicz W., Karczewski G., Jeżewski M., Witkowska B., Mycielski A.
Acta Physica Polonica A
|
1991
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vol. 79
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issue 2-3
369-372
EN
Reflectivity spectra of HgSe crystals highly doped with Ga and Fe, respectively, were investigated in the spectral region close to the absorption edge at temperatures between 12 K and 295 K. From the analysis of the structure observed in reflectivity the temperature dependence of the Fermi energy was determined for both kinds of crystals.
11
Content available remote

Composition Dependence of the Energy Gap in HgFeSe - Optical Verification

88%
Szuszkiewicz W., Julien C., Bałkanski M., Dybko K., Witkowska B.
Acta Physica Polonica A
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1992
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vol. 82
|
issue 5
757-760
EN
Infrared reflectivity was investigated for the mixed Hg_{1-x}Fe_{x}Se crystals for x < 0.1. The theoretical analysis of the experimental curves suggests opening of the energy gap for the composition x = 0.087 at the temperature close to 80 K.
12
Content available remote

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

88%
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.
13
Content available remote

Elastic Constants of β-HgS

76%
Prieur J., Joffrin J., Szuszkiewicz W., Dynowska E., Górecka J., Witkowska B.
Acta Physica Polonica A
|
1998
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vol. 94
|
issue 3
487-491
EN
The elastic constants of single crystals of β-HgS highly doped with iron were directly determined at room temperature from the measurements of ultrasonic wave velocities by the pulse-echo technique. The values of c_{11}=6.750, c_{12}=5.186, and c_{44}=2.42 (given at 10^{10} N m^{-2} units) were obtained and compared with the experimental data taken for other mercury chalcogenides. The elastic characteristics of this group of materials is quite similar to those of Cd and Zn chalcogenides.
14
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Pressure Study of Charged Donor Ordering in HgSe Doped with Iron and Gallium

76%
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.
15
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Preparation and Luminescent Properties of ZnTe-Cd_{1-x}Mn_{x}Te_{1-y}Se_{y} Heterojunction

76%
Le K., Dobrowolski W., Witkowska B., Mycielski A., Galązka R., Nguyen K.
Acta Physica Polonica A
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1995
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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}.
16
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Content available

Pb_{1-x}Mn_xTe Crystals as a New Thermoelectric Material

76%
Osinniy V., Jędrzejczak A., Domuchowski W., Dybko K., Witkowska B., Story T.
Acta Physica Polonica A
|
2005
|
vol. 108
|
issue 5
809-816
EN
We studied experimentally thermoelectric properties of p-type bulk crystals of Pb_{1-x}Mn_xTe and Pb_{1-x-y}Ag_yMn_xTe (0≤ x≤ 0.083 and y≤0.017) at room and liquid nitrogen temperatures. Model calculations of the thermoelectric figure of merit parameter (Z) involved the analysis of carrier concentration, carrier mobility, density of states as well as electronic and lattice contributions to the thermal conductivity of PbMnTe. In the analysis we took into account the main effect of Mn concentration on the band structure parameters of PbMnTe, i.e. the increase of the energy gap. The analysis of electrical, thermoelectric, and thermal properties of Pb_{1-x}Mn_xTe crystals showed that, at room temperature, the maximum values of the parameter Z occur in crystals with Mn content 0.05≤ x≤0.07 and are comparable with a maximal value of Z observed in PbTe. At T=400 K the increase in the parameter Z by 10% is expected in Pb_{1-x}Mn_xTe crystal (as compared to PbTe) for a very high concentration of holes of about p=5×10^{19} cm^{-3}. The experimental data correctly reproduce the theoretical Z(p) dependence.
17
Content available remote

Electronic Band Structure of Cubic HgS

76%
Guziewicz E., Kowalski B., Orłowski B., Dybko K., Witkowska B., Szuszkiewicz W.
Acta Physica Polonica A
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1995
|
vol. 87
|
issue 2
395-398
EN
Reflectivity spectra of Hg_{1-x}Fe_{x}S (x < 0.04) and HgSe_{1-y}S_{y} (y < 0.5) mixed crystals were measured in the vacuum ultraviolet energy range from 4 to 12 eV. Information about the electronic band structure of cubic modi­fication of HgS resulting from the above data is analyzed and discussed.
18
Content available remote

Iron Impurity Related Optical Transitions in HgSe:Fe

76%
Szuszkiewicz W., Julien C., Balkanski M., Arciszewska M., Witkowska B., Mycielski A.
Acta Physica Polonica A
|
1991
|
vol. 80
|
issue 3
437-440
EN
Fe^{2+} crystal field transitions and the heavy hole valence band to the Fe level transitions (e + Fe^{3+} → Fe^{2+}) have been observed and discussed for HgSe doped with iron.
19
Content available remote

Do the Mixed Crystals HgSeS Exhibit the One-Mode Behavior?

76%
Szuszkiewicz W., Witowski A., Julien C., Balkanski M., Dybko K., Witkowska B., Mycielski A.
Acta Physica Polonica A
|
1992
|
vol. 82
|
issue 5
887-889
EN
The low-temperature far-infrared reflectivity spectra of HgSe and HgSeS are measured and analysed. The results suggest the one-mode behavior of phonon excitations in HgSeS mixed crystals.
20
Content available remote

Local Modes of Transition Metal Ions (Mn, Fe, Co) in Mercury Chalcogenides

76%
Szuszkiewicz W., Dybko K., Dynowska E., Witkowska B., Jouanne M., Julien C.
Acta Physica Polonica A
|
1995
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vol. 88
|
issue 5
937-940
EN
Optical phonons in mercury chalcogenides doped with selected transition metal ions are investigated by infrared reflectivity and Raman scattering measurements performed at helium temperatures. The results obtained for Hg_{1-x}Fe_{x}Se, Ηg_{1-x}Co_{x}Se, Ηg_{1-x}Fe_{x}S and Hg_{1-x}Co_{x}S mixed crystals demonstrate the significant influence of the 3d electron correlation effects and/or sp-d hybridization on the transition metal ion local mode frequency.
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