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  1. 49 Acta Physica Polonica A

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  1. 8 Mašek J.

  2. 7 Máca F.

  3. 6 Kaczkowski J.

  4. 6 Sznajder M.

  5. 5 Glukhov K.

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1
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Valency of Yb in PbS and PbTe Determined by XPS

100%
Gołacki Z., Heinonen M.
Acta Physica Polonica A
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1997
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vol. 91
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issue 4
775-778
EN
X-ray photoelectron spectroscopy experiments on PbTe:Yb, PbS:Yb, PbTe, and PbS crystals have been performed using the monochromatized Al K_{α} radiation. The valence band spectrum of PbTe:Yb exhibits one set of peaks associated with divalent Yb initial states, but two sets associated with divalent and trivalent Yb are observed for PbS:Yb. The valency of Yb in PbTe:Yb is 2 (within an accuracy of the experiment) but in PbS:Yb the mixed valency of Yb is seen. These conclusions are confirmed by an analysis of Yb 4d spectra in PbTe:Yb and PbS:Yb crystals.
2
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Electronic Structure and Optical Properties of GaAs_{1-x}N_x and Ga_{1-x}B_xAs Alloys

100%
Gonzalez Szwacki N., Bogusławski P., Gorczyca I., Christensen N., Svane A.
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issue 4-5
633-641
EN
The electronic band structure of GaAs_{1-x}N_x (x=0.016 and 0.031) and Ga_{1-x}B_xAs (x= 0.031) is studied by ab initio calculations using a supercell approach. Based on ab initio calculations and group theory we present a comprehensive analysis of the electronic structure of GaAs:N and GaAs:B alloys. In particular, we study the effective mass of conduction electrons in GaAs:N as a function of pressure and the Fermi energy. We find that the lowest conduction band is strongly non-parabolic, which leads to an increase in the effective mass with the electron energy. The rate of the increase is enhanced by the hydrostatic pressure. Theoretical results are compared to experimental data, and a qualitative agreement is found.
3
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Changes of Electronic Structure of SnTe Due to High Concentration of Sn Vacancies

100%
Mašek J., Nuzhnyj D. N.
Acta Physica Polonica A
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1997
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vol. 92
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issue 5
915-918
EN
Non-stoichiometric Sn_{1-y}Te is a strongly degenerated n-type semiconductor. This is important for understanding unusual features of magnetic behaviour of Sn_{1-x}Gd_{x}Te where the relative positions of the Fermi energy and the atomic d-level of Gd govern the exchange coupling. The influence of the Sn vacancies on the band structure cannot be neglected if their concentration reaches a few atomic percent. We address this problem by using a tight-binding coherent potential approach and show that although the character of the bands remains unchanged, they are modified so that ε_{d} can come out above the heavy-hole band.
4
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Electrical and Thermoelectrical Properties of TlIn_{1-x}Yb_xTe₂ (0 ≤ x ≤ 0.10) Solid Solutions in the Temperature Range of 80-1000 K

100%
Aliev F., Yuzbashov E., Agayeva U., Zarbaliev M.
Acta Physica Polonica A
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2016
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vol. 129
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issue 1
69-74
EN
The temperature dependence of the electrical conductivity σ , the Hall coefficient R and the thermopower coefficient α in the solid solutions TlIn_{1-x}Yb_xTe₂ (0 ≤ x ≤0.10) have been investigated in the temperature range of 80-1000 K. The effective masses of electrons and holes have been determined on the basis of the kinetic parameters. It was established that starting from x = 0.05 the solid solutions of TlIn_{1-x}Yb_xTe₂ belong to narrow-gap semiconductors having high values of the interaction matrix element. It is shown that the samples of TlIn_{1-x}Yb_xTe₂ in the region of 0.10 ≥ x ≥ 0.05 are promising materials for the energy converters operating at high temperatures.
5
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Investigation of the Characteristics of the Boron Doped MnO Films Deposited by Spray Pyrolysis Method

100%
Bedir M., Tunç A., Öztas M.
Acta Physica Polonica A
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2016
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vol. 129
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issue 6
1159-1164
EN
Boron doped MnO films were prepared by spray pyrolysis technique at 375°C substrate temperature, which is a low cost and large area technique to be well-suited for the manufacture of solar cells, using boric acid (H₃BO₃) as dopant source, and their properties were investigated as a function of doping concentration. Boron doping was achieved by adding 0.1 M, 0.2 M, 0.3 M, and 0.4 M H₃BO₃ to the starting solution. X-ray analysis showed that the films were polycrystalline fitting well with a cubic structure and have preferred orientation in (111), (220) and (311) directions. Optical band gap of the undoped and B-doped MnO films were found to vary from 2.25 to 2.54 eV. The changes observed in the energy band gap and structural properties of the films related to the boric acid concentration are discussed in detail.
6
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Valence Band Density of States and Mn 3d Contribution in Mn_{1-x}Mg_{x}Te

100%
Kowalski B., Guziewicz E., Kopalko K., Orłowski B., Janik E., Wojtowicz T., Johnson R.
Acta Physica Polonica A
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1998
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vol. 94
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issue 3
401-405
EN
Resonant photoemission spectroscopy was applied to determine the Mn 3d derived contribution to the valence band density of states of Mn_{0.44} Mg_{0.56}Te grown by molecular beam epitaxy on a GaAs(001) substrate. The modifications of the valence band density-of-states distribution are discussed as a consequence of the substitution of Mg ions for Mn ions.
7
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Contribution of Mn 3d Electrons To the Valence Band of Sn_{0.9}Mn_{0.1}te

100%
Nadolny A., Guziewicz E., Kowalski B., Orłowski B., Johnson R.
Acta Physica Polonica A
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1998
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vol. 94
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issue 3
454-458
EN
The synchrotron radiation in the energy range between 15 and 70 eV was used to investigate the electronic structure of the crystalline Sn_{0.9}Mn_{0.1}Te by means of the resonant photoemission spectroscopy. Fano-type resonance has been observed in the obtained constant initial energy curves with the resonant energy 50.6 eV and antiresonant energy 49.0 eV. The energy distribution curves taken at photon energies close to the Mn 3p-3d transitions allow us to conclude that Mn atoms contribute to the valence band mainly at energies of 4.0 eV and 7.8 eV below the valence band edge.
8
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Correlated Doping in Semiconductors: the Role of Donors in III-V Diluted Magnetic Semiconductors

80%
Mašek J., Turek I., Drchal V., Kudrnovský J., Máca F.
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issue 4-5
673-678
EN
We investigate the compositional dependence of the total energy of the mixed crystals (Ga,Mn)As co-doped with As, Sn, and Zn. Using the ab initio linear muffin-tin orbital coherent potential approximation method we find a correlation between the incorporation of acceptors (Mn, Zn) and donors (Sn, antisite As). In particular, the formation energy of As_{Ga} is reduced by approximately 0.1 eV in the presence of Mn, and vice versa. This leads to the self-compensating behavior of (Ga,Mn)As.
9
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Disorder-Induced Effects in III-V Semiconductors with Mn

80%
Mašek J., Máca F.
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issue 4-5
667-672
EN
The substitution of Mn in the III-V diluted magnetic semiconductors leads to a strong electron scattering on impurities. Besides the features induced in the valence band by the hybridization with the Mn d-states, also the conduction band is affected by the absence of the Mn s-states at its edge. Also the high concentration of compensating donors modifies the band structure. This is shown on the absorption coefficientε_2(ω) of GaP doped with Mn and Se. The absorption evaluated by ab initio density functional calculations starts with a smooth tail and does not show the structure typical of III-V materials. We analyze these features and the role of the donors on model systems using the tight-binding coherent potential approach.
10
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Measurement of Very Small Zeeman Splittings in GaN:Mn,Mg by Faraday Rotation

80%
Wołoś A., Kossacki P., Golnik A., Kamińska M., Gaj J., Twardowski A., Grzegory I., Boćkowski M., Porowski S.
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issue 4-5
695-699
EN
In this work we demonstrate an application of Faraday rotation for measuring an extremely small Zeeman splitting of an Mn related absorption line placed at 1.417 eV in optical absorption spectrum of Mn and Mg doped gallium nitride. Analysis of the collected spectra allowed us to determine the value of the splitting as equal to 0.12±0.01 meV at 6 T. This data should help in establishing the nature of the observed absorption band.
11
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Gain Spectrum for the In_4Se_3 Crystal with a Non-Standard Dispersion Law of Charge Carriers

80%
Bercha D., Glukhov K., Sznajder M.
Acta Physica Polonica A
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2011
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vol. 119
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issue 5
720-722
EN
Based upon the ab initio band structure calculations results and the density of states function of the orthorhombic In_4 Se_3 crystal as well as the experimental data concerning its radiative recombination, it was shown that the Bernard-Durafour condition is fulfilled for this crystal. The absorption coefficient α that exhibits a negative value in the given energy range and for the given concentrations of non-equilibrium charge carriers, was calculated.
12
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Electronic Structure of Some Wurtzite Semiconductors: Hybrid Functionals vs. Ab Initio Many Body Calculations

80%
Kaczkowski J.
Acta Physica Polonica A
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2012
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vol. 121
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issue 5-6
1142-1144
EN
Using the first-principles projector augmented wave method, the structural and electronic properties of wurtzite crystals, AlN, GaN, InN and ZnO have been calculated. Different exchange-correlation approximations: LDA, LDA+U, GGA, GGA+U and hybrid Heyd-Scuseria-Ernzerhof method were used. We also present the values of band gap calculated within different GW approximations (G_0W_0, GW_0, GW and U+G_0W_0, the last one for materials with shallow d states). In case of structural parameters the best agreement with experiment was obtained for hybrid Heyd-Scuseria-Ernzerhof functional and in case of band gap the best agreement was for GW and U+G_0W_0 approximation.
13
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Thin Films Based on Nanocrystalline TiO_{2} for Transparent Electronics

80%
Prociow E., Sieradzka K., Domaradzki J., Kaczmarek D., Mazur M.
Acta Physica Polonica A
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2009
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vol. 116
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issue S
S-72-S-74
EN
In this work, investigations of structural, optical and electrical properties of transparent oxide semiconductor thin films based on TiO_{2} doped with Eu, Pd and Tb, Pd have been presented. The transparent oxide semiconductor nanocrystalline thin films were prepared by magnetron sputtering process. It was shown that doping with selected elements results in semiconducting properties of prepared thin films of oxides with p-(TiO_{2}:(Tb, Pd)) or n-type (TiO_{2}:(Eu, Pd)) of electrical conduction.
14
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Seebeck Coefficient and Optical Studies of Cadmium Doped CuInS_{2} Single Crystal

80%
Chaki S.
Acta Physica Polonica A
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2009
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vol. 116
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issue 2
221-225
EN
Single crystals of CuInS_{2} were successfully grown by chemical vapor transport technique using iodine as transporting agent. The as-grown chemical vapor transport CuInS_{2} single crystals were found to have large resistivity. To decrease the resistivity of the crystals they were doped with three different cadmium concentrations. Seebeck coefficient variation with temperature is measured for all the three doped samples. Optical bandgaps were determined for these three doped samples using optical absorption spectra. The obtained results are discussed in detail.
15
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The Surface Hydro-Oxidation of LaNiO_{3-x} Thin Films

80%
Mickevičius S., Grebinskij S., Bondarenka V., Lisauskas V., Šliužienė K., Tvardauskas H., Vengalis B., Orłowski B., Osinniy V., Drube W.
Acta Physica Polonica A
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2007
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vol. 112
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issue 1
113-120
EN
The high-energy X-ray photoelectron spectroscopy was used to determine the composition and chemical structure of epitaxial LaNiO_{3-x} films obtained by a reactive dc magnetron sputtering. It was found that the oxide and hydroxide species of La and Ni are on the films surface. The thickness of hydroxide enriched layer, estimated from the oxide and hydroxide peak intensities, is about 2 nm.
16
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Terahertz Resonant Detection by Plasma Waves in Nanometric Transistors

80%
Teppe F., El Fatimy A., Boubanga S., Knap W., Seliuta D., Valusis G., Chenaud B.
Acta Physica Polonica A
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2008
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vol. 113
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issue 3
815-820
EN
The plasma waves in gated two-dimensional electron gas have a linear dispersion law, similar to the sound waves. The transistor channel is acting as a resonator cavity for the plasma waves, which can reach frequencies in the THz range for a sufficiently short gate length field effect transistors. A variety of possible applications of field effect transistor operating as a THz device were suggested. In particular, it was shown that the nonlinear properties of plasma oscillations can be utilized for THz tunable detectors. During the last few years THz detection related to plasma wave instabilities in nanometer size field effect transistors was demonstrated experimentally. In this work we review our recent experimental results on the resonant plasma wave detection at cryogenic and room temperatures.
17
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Compositional Dependence of the Formation Energies of Substitutional and Interstitial Mn in Partially Compensated (Ga,Mn)As

80%
Mašek J., Turek I., Kudrnovský J., Máca F., Drchal V.
Acta Physica Polonica A
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2004
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vol. 105
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issue 6
637-644
EN
We use the density-functional theory to calculate the total energy of mixed crystals (Ga,Mn)As with a small concentration of various donors. We find that the formation energy of Mn depends strongly on the partial concentrations of Mn in the substitutional and interstitial positions, and on the concentration of other dopants. The composition dependence of the formation energies represents an effective feedback mechanism, resulting in the self-compensation property of (Ga,Mn)As. We show that the partial concentrations of both substitutional and interstitial Mn increase proportionally to the total concentration of Mn.
18
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Field Dependence of Spin Lifetimes in Wurtzite Materials

80%
Majewski J.
Acta Physica Polonica A
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2005
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vol. 108
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issue 5
777-780
EN
We present first-principles calculations of the zero field spin splitting of energy bands in wurtzite materials. Our calculations reveal that the huge electric fields originating from strong piezo- and pyroelecric character of nitrides do not increase the spin splitting of bands in nitride heterostructures. This implicates long spin lifetimes in quantum structures based on these materials and weak possibility of tuning with external electric field.
19
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Lattice Expansion of (Ga,Mn)As: The Role of Substitutional Mn and of the Compensating Defects

80%
Mašek J., Máca F.
Acta Physica Polonica A
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2005
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vol. 108
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issue 5
789-794
EN
We apply the density-functional technique to determine the lattice constant of GaAs supercells containing Mn_{Ga}, Mn_{int}, and As_{Ga} impurities, and use a linear interpolation to describe the dependence of the lattice constant a of Ga_{1-x}Mn_{x}As on the concentrations of these impurities. The results of the supercell calculations confirm that Mn_{Ga} does not contribute to the lattice expansion. The increase in a is due to both Mn_{int} and As_{Ga}, that are both created in the as-grown (Ga,Mn)As in proportion to x, and that are most probably present in a remarkable amount also in the best annealed materials.
20
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Low-Temperature Scanning Tunneling Spectroscopy of Semiconductor Surfaces

80%
Feenstra R., Meyer G., Moresco F., Rieder K.
Acta Physica Polonica A
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2003
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vol. 104
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issue 3-4
205-216
EN
Low-temperature scanning tunneling spectroscopy measurements on semiconductor surface are described. We consider both surfaces which do not possess surface states within the bulk bandgap, such as GaAs(110), and surfaces which do have states within the gap, such as Ge(111) 2×1 and Ge(111)c(2×8). Band bending in the semiconductor due to the electric field in the vacuum penetrating the semiconductor is found to be a substantial effect in the former case. Transport limitations in the semiconductor give rise to additional voltage drops, which can be observed by making measurements over a wide range of tunnel current magnitudes.
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