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Wyświetlanie 1-15 z 73
Tytuł:
Improvement of Electrical Properties of Hg$\text{}_{1-x}$Zn$\text{}_{x}$Se upon Doping with Fe
Autorzy:
Dobrowolski, W.
Grodzicka, E.
Kossut, J.
Witkowska, B.
Powiązania:
https://bibliotekanauki.pl/articles/1921589.pdf
Data publikacji:
1992-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.80.Ey
72.20.Fr
71.55.Fr
Opis:
Results of measurements of electron concentration and mobility in mixed crystals of Hg$\text{}_{1-x}$Zn$\text{}_{x}$Se (0 ≤ x ≤ 0.07) doped with resonant Fe donors (0 ≤ n$\text{}_{Fe}$ ≤ 5 × 10$\text{}^{19}$ cm$\text{}^{-3}$) 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.
Źródło:
Acta Physica Polonica A; 1992, 82, 4; 681-684
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Metastability of Localized Neutral Donor State In GaAs
Autorzy:
Skierbiszewski, C.
Jantsch, W.
Lübke, K.
Wilamowski, Z.
Suski, T.
Powiązania:
https://bibliotekanauki.pl/articles/1933994.pdf
Data publikacji:
1995-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.20.Fr
71.55.-i
Opis:
Investigations of the photoconductivity of GaAs:Ge under hydrostatic pressure show, in addition to the well known persistent photoconductivity due to the DX state, another giant photoconductivity caused by a neutral localised "A₁" state of the donor. We find that the top of the barrier for the electron recapture to the Α₁ state is pinned to the conduction band edge and the capture cross-section σ(T → ∞) is surprisingly small.
Źródło:
Acta Physica Polonica A; 1995, 88, 5; 905-908
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Helical Spin Structures in c-Axis Dy/Y Superlattice
Autorzy:
Seroczyńska, M.
Kociński, J.
Powiązania:
https://bibliotekanauki.pl/articles/1943983.pdf
Data publikacji:
1996-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.70.Fr
75.70.-i
Opis:
On the basis of Landau's theory of symmetry changes at continuous phase transitions, we have derived the formulae for two incommensurate helical spin structures which are symmetry allowed in Dy/Y superlattice, when the helical axis is parallel to the c-axis of the hexagonal lattice. These structures have different extinction coefficients in their cross-sections for magnetic scattering of neutrons and therefore can be distinguished by experiment. Magnetic satellite peaks around the reciprocal lattice points K + 0 are allowed for only one of these spin structures, namely that inferred from earlier experiments.
Źródło:
Acta Physica Polonica A; 1996, 89, 1; 99-104
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Temperature Dependent Electron Beam Induced Current Study of Defects in Silicon
Autorzy:
Sekiguchi, T.
Kusanagi, S.
Miyamura, Y.
Sumino, K.
Powiązania:
https://bibliotekanauki.pl/articles/1924321.pdf
Data publikacji:
1993-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.55.Fr
72.80.Cw
Opis:
A new computer-aided electron beam induced current system was developed which makes it possible to obtain two-dimensional mapping of the absolute magnitudes of electron beam induced current signals over the temperature range 15 K-400 K. Electronic states of defects in cast silicon and deformation-induced dislocations in float-zone silicon were investigated from the analyses of temperature dependencies of electron beam induced current contrasts of the defects measured with the system. Electron beam induced current active defects in cast Si were identified to be Fe impurity atoms or Fe-B pairs incorporated at the dislocation core depending on the cooling rate of a crystal. Dislocations in float-zone silicon were shown to have an energy level for carrier recombination in the lower half of the band gap.
Źródło:
Acta Physica Polonica A; 1993, 83, 1; 71-79
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Structural Study of (NH$\text{}_{4}$)$\text{}_{4}$H$\text{}_{2}$(SeO$\text{}_{4}$)$\text{}_{3}$ in the Low-Temperature Phase
Autorzy:
Fukami, T.
Higa, N.
Chen, R. H.
Powiązania:
https://bibliotekanauki.pl/articles/2013261.pdf
Data publikacji:
2000-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.66.Fn
64.60.Fr
Opis:
The crystal structure of tetraammonium dihydrogen triselenate, (NH$\text{}_{4}$)$\text{}_{4}$H$\text{}_{2}$(SeO$\text{}_{4}$)$\text{}_{3}$, in the low-temperature phase at 141 K is studied by X-ray diffraction. The space group symmetry (triclinic P1) and the structure parameters are determined. By the shift of the Se atom from the center of the SeO$\text{}_{4}$ tetrahedron, it is suggested that the (NH$\text{}_{4}$)$\text{}_{4}$H$\text{}_{2}$ (SeO$\text{}_{4}$)$\text{}_{3}$ crystal in the low-temperature phase is ferroelectric with the electric dipole moment along the c-axis. The rotation of the SeO$\text{}_{4}$ tetrahedron suggested by electron paramagnetic resonance measurements is discussed.
Źródło:
Acta Physica Polonica A; 2000, 97, 4; 663-670
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Low Field Relaxational Behavior of Taap Single Crystal (20-10$\text{}^{6}$ Hz)
Autorzy:
Fernández del Castillo, J. R.
Iglesias, T.
Przesławski, J.
Gonzalo, J. A.
Powiązania:
https://bibliotekanauki.pl/articles/1968856.pdf
Data publikacji:
1998-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
64.60.Fr
77.80.-e
Opis:
Relaxational behavior of ferroelectric telluric acid ammonium phosphate crystals were investigated in the range 20 Hz to 1 MHz by means of low field measurements of ε' and tan δ in the vicinity of ferroelectric phase transitions at a number of frequencies. Results are compared with those for triglycine selenate, a much "softer" ferroelectric material. The measuring field and frequency dependence of the effective potential barrier height for domain wall motion are compared in both crystals.
Źródło:
Acta Physica Polonica A; 1998, 93, 3; 499-503
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Using a Bent Tube as an Energy Filter for a Positron Beam. Simulations on Determining the Optimum Angle of the Bend
Autorzy:
Dinescu, D.
Djourelov, N.
Powiązania:
https://bibliotekanauki.pl/articles/1033242.pdf
Data publikacji:
2017-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
41.75.Fr
78.70.Bj
Opis:
One way to perform lifetime measurements at a DC positron beam is to pass positrons through a pulsing device. The compressed e⁺ bunches are accelerated to a desired energy for depth profiling of the studied sample. A fraction of the e⁺ that are backscattered from the sample surface can travel back through the uniform magnetic field that is generated along the central axis of the beam transport lines and reach the accelerator. The backscattered e⁺ that reach the accelerator can be re-accelerated towards the sample and re-implant in it with a delay from the initial implanted e⁺ bunch. These e⁺ that are re-implanted into the sample with a delay cause distortions in the lifetime spectra. A setup which uses a bent tube to act as an energy filter to reduce the effect of the backscattered e⁺ is studied by simulations. The simulations are performed in order to find the optimum geometry for minimum distortions.
Źródło:
Acta Physica Polonica A; 2017, 132, 5; 1624-1627
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Coulomb versus Madelung Gap: Ordering in a System of Point Charges
Autorzy:
Sobkowicz, P.
Wilamowski, Z.
Kossut, J.
Powiązania:
https://bibliotekanauki.pl/articles/1929618.pdf
Data publikacji:
1993-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.55.-i
72.20.Fr
Opis:
Spatial correlations of impurity charges in a mixed valence regime are studied with the use of Monte Carlo simulations. The influence of various kinds of disorder on the one-particle density of states is determined. A continuous transitions from a "soft" Coulomb gap (density of states vanishing only at the chemical potential) to a "hard" gap (with a finite range of energies with vanishing density of states) is found, driven by decreasing amount of built-in disorder in the system. The "hard" Coulomb gap resembles the Madelung gap, found in crystalline arrangements of charges. The similarity reflects the fact that both the Coulomb and Madelung gaps are manifestations of the same phenomenon, resulting from ordering of the positions of point charges, the only difference being the range of correlations.
Źródło:
Acta Physica Polonica A; 1993, 84, 3; 515-518
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Crystal Structure of K$\text{}_{3}$Na(SeO$\text{}_{4}$)$\text{}_{2}$ at 340 K
Autorzy:
Fukami, T.
Chen, R. H.
Powiązania:
https://bibliotekanauki.pl/articles/1993089.pdf
Data publikacji:
1998-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.66.Fn
64.60.Fr
Opis:
The crystal structure of tripotassium sodium diselenate, K$\text{}_{3}$Na(SeO$\text{}_{4}$)$\text{}_{2}$, at 340 K is studied by single-crystal X-ray diffraction. The space group symmetry (trigonal P3̅) and structure parameters are determined. It is found that there exists the difference of the direction and the magnitude of the atomic displacement at the two phase transitions of 346 K and 334 K.
Źródło:
Acta Physica Polonica A; 1998, 94, 5-6; 795-801
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Structural Phase Transition and Crystal Structure for (ND$\text{}_{4}$)$\text{}_{4}$D$\text{}_{2}$(SeO$\text{}_{4}$)$\text{}_{3}$ at Low Temperature
Autorzy:
Fukami, T.
Chen, R. H.
Powiązania:
https://bibliotekanauki.pl/articles/2027434.pdf
Data publikacji:
2001-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.66.Fn
64.60.Fr
Opis:
Differential scanning calorimetry and X-ray diffraction measurements were performed on a deuterated tetraammonium dihydrogen triselenate (ND$\text{}_{4}$)$\text{}_{4}$D$\text{}_{2}$(SeO$\text{}_{4}$)$\text{}_{3}$ crystal at low temperatures. A structural phase transition is found at 182.0(3) K. The space group symmetry (triclinic P1) and the structure parameters are determined at 145 K in the low-temperature phase. The isotope effect for an asymmetric O-H-O hydrogen bond by the substitution of deuterium is discussed.
Źródło:
Acta Physica Polonica A; 2001, 100, 1; 53-65
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
RKKY-like Biquadratic Exchange in Magnetic Superlattices
Autorzy:
Gruhn, W.
Bąk, Z.
Jaroszewicz, R.
Powiązania:
https://bibliotekanauki.pl/articles/1945268.pdf
Data publikacji:
1996-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.70.Cn
75.70.Fr
Opis:
We show that in magnetic metallic superlattices along with the bilinear RKKY-reminiscent interaction between magnetic superlattices there can be an important quadrupole-quadrupole coupling. In an analytical way we derive the range functions of the quadrupol-quadrupole interaction and discuss its relation to magnetoresistivity.
Źródło:
Acta Physica Polonica A; 1996, 89, 3; 417-420
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Lattice Misfit Strain as Origin for Biquadratic Interlayer Coupling
Autorzy:
Jaroszewicz, R.
Bąk, Z.
Gruhn, W.
Powiązania:
https://bibliotekanauki.pl/articles/1945269.pdf
Data publikacji:
1996-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.70.Cn
75.70.Fr
Opis:
The direct observations of some MBE grown superlattices show large interfacial undulations, which is attributed to the elastic relaxation of tensile layers. Assuming that the interface lateral lattice deformation, due to ionic radii misfit, is given by the periodic solution of the Frenkel-Kontorova model, we calculate the magnetoelastic contribution to the biquadratic magnetic coupling between ferromagnetic layers across the nonmagnetic spacer. We show that due to the correlated modulations of the effective bilinear exchange integral, there arises a biquadratic exchange which favours perpendicular orientations of magnetization in adjacent ferromagnetic layers.
Źródło:
Acta Physica Polonica A; 1996, 89, 3; 421-424
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Evidence for Alloy Splitting of Ge Related DX State in Al$\text{}_{x}$Ga$\text{}_{1-x}$As
Autorzy:
Skierbiszewski, C.
Piotrzkowski, R.
Lubke, K.
Powiązania:
https://bibliotekanauki.pl/articles/1992190.pdf
Data publikacji:
1998-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.55.-i
72.20.Fr
Opis:
Thermal emission from resonant DX levels in Ge-doped GaAlAs was studied by measuring the temperature transients of free electron concentration. Pressure was used to fill the levels with electrons. Two emission peaks are observed in AlGaAs:Ge. This enables us to confirm that Ge, similarly to Si dopant, is stabilized upon dangling bond C$\text{}_{3v}$ configuration in AlGaAs. Analysis of experimental data allows us to determine parameters of two components of the DX multilevel system. Evaluated alloy splitting of ground and top of the barrier states: 45 meV is comparable with determined for Si donor.
Źródło:
Acta Physica Polonica A; 1998, 94, 3; 531-533
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electrical Properties of InGaP Doped with Si
Autorzy:
Litwin-Staszewska, E.
Trzeciakowski, W.
Piotrzkowski, R.
Gonzalez, L.
Powiązania:
https://bibliotekanauki.pl/articles/1991938.pdf
Data publikacji:
1998-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.20.Fr
72.80.Ey
71.55.Eq
Opis:
We measured Hall concentration n in InGaP:Si epitaxial layers grown by MBE as a function of pressure P up to 2 GPa and of temperature T from 77 to 300 K. We interpreted our results in terms of the broad distribution of impurity states resonant with the conduction band. From the low-temperature n(P) dependence we can directly obtain the total density of impurity states around the Fermi level ρ(E$\text{}_{F}$). The Fermi level can be shifted with respect to impurity states by applying pressure and by using samples with different n. In this way we obtain ρ(E) in a wide energy range. We discuss the possible reasons for the observed broad distribution of ρ(E).
Źródło:
Acta Physica Polonica A; 1998, 94, 3; 431-435
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Monte Carlo Study of a Periodically Pinned 2D Superconductor
Autorzy:
Rezlescu, N.
Anghelache, R.
Ciobotaru, I.
Powiązania:
https://bibliotekanauki.pl/articles/1955503.pdf
Data publikacji:
1997-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
64.60.Fr
75.10.Hk
74.25.Bt
Opis:
We show that a natural assumption on the moving mechanism of vortices in a periodically pinned, two-dimensional superconductor in the mixed state is the basis for a n-clock-like model. The pinning points are considered to be centered in each unit cell of the superconducting lattice. This property enables one to use a discrete version of the XY model used in the simulations focusing on the melting of the Abrikosov lattice of vortices in a system of Josephson arrays. A Monte Carlo study performed on the corresponding Hamiltonian in a field given by a filling factor of f=1/2 exhibits two phase transitions, at the temperatures T$\text{}_{c1}$≈0.325 and T$\text{}_{m}$≈0.65. The numerical estimation of the Challa parameters for both transitions indicates their continuous nature. The physical meaning of the lower transition is the expulsion of the magnetic field from the superconducting system, i.e. the Meissner effect. The physical equivalent of the upper transition is the melting of the pinned vortex lattice.
Źródło:
Acta Physica Polonica A; 1997, 91, 2; 337-340
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 73

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