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Wyświetlanie 1-15 z 65
Tytuł:
AC Electrical Conductivity and Dielectric Properties of Perovskite $(Pb,Ca)TiO_3$ Ceramic
Autorzy:
El-Mallah, H.
Powiązania:
https://bibliotekanauki.pl/articles/1419850.pdf
Data publikacji:
2012-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.45.Gm
72.20.-i
72.80.-r
Opis:
$Pb_{1 - x }Ca_{x}TiO_3$ perovskite crystalline structure with x = 0, 0.2, 0.6, 0.7, and 0.8 were prepared by mixture method. The ac conductivity and dielectric properties of the studied bulk compositions have been investigated in the frequency range $1 \times 10^3 - 5 \times 10^6 Hz$ and temperature range 303-473 K. The experimental results indicate that the ac conductivity $\sigma_{ac}(\omega),$ dielectric constant ε' and dielectric loss ε" depend on the temperature and frequency. The ac conductivity was found to obey the power law $\omega^{S}$ with the frequency exponent S > 1 decreasing with increasing temperature. The present results are compared to the principal theories that describe the universal dielectric response behavior. Values of dielectric constant ε' and dielectric loss ε" were found to be temperature and frequency dependent and the maximum barrier height $W_{m}$ is calculated.
Źródło:
Acta Physica Polonica A; 2012, 122, 1; 174-179
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Analytical Band Model in Monte Carlo Simulation of Electric Transport in ZnS Thin Film Electroluminescent Devices
Autorzy:
Zhao, H.
Wang, Y.
Xu, X.
Powiązania:
https://bibliotekanauki.pl/articles/2014087.pdf
Data publikacji:
2000-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.60.-b
72.20.-i
Opis:
In this paper, an analytical band model is introduced in Monte Carlo simulation of electric transport process in thin film electroluminescent devices. The band structure of ZnS calculated from the empirical pseudopotential method is fitted by using polynomials. The density of states and scattering rates are also calculated from these polynomials. Based on these results, the electric transport process in ZnS-type thin film electroluminescent devices is simulated through the Monte Carlo method. By comparison with others, this model is as fast as the nonparabolic model and as accurate as the full band model. Furthermore, the influence of the band model on the simulation results is also investigated. We show that the dispersion relation and density of states are all important in the simulation.
Źródło:
Acta Physica Polonica A; 2000, 98, 1-2; 123-130
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Anomalous Hall Effect in IV-VI Semiconductors
Autorzy:
Dyrdał, A.
Dugaev, V.
Barnaś, J.
Brodowska, B.
Dobrowolski, W.
Powiązania:
https://bibliotekanauki.pl/articles/1810533.pdf
Data publikacji:
2009-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.20.-i
75.50.Pp
72.25.Dc
Opis:
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.
Źródło:
Acta Physica Polonica A; 2009, 115, 1; 287-289
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Complex Impedance Investigation of Epitaxial LCMO Thin Films
Autorzy:
Mateev, E.
Nurgaliev, T.
Blagoev, B.
Powiązania:
https://bibliotekanauki.pl/articles/1205437.pdf
Data publikacji:
2014-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.20.-i
72.80.Ga
72.90.+y
73.61.Le
Opis:
Epitaxial $La_{0.67}Ca_{.33}MnO_3$ (LCMO) thin films by off-axis magnetron sputtering were deposited on $SrTiO_3$ (STO) substrates. Complex impedance measurements (module and phase of the thin film impedance) in frequency range 1-30 kHz are done. Substantial dependence of both: module and phase of the complex surface impedance is observed. The temperature interval scanned is from 77 K to room temperature. The impedance has inductive behavior for temperatures less than the Curie temperature and capacitive for higher temperatures. Reduction of the film thickness from 60 to 30 nm shifts the impedance curves to the lower temperatures.
Źródło:
Acta Physica Polonica A; 2014, 126, 3; 787-789
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Concentration Anomalies of Properties in Pb$\text{}_{1-x}$Ge$\text{}_{x}$Te Solid Solutions
Autorzy:
Rogacheva, E. I
Sinelnik, N. A
Nashchekina, O. N.
Powiązania:
https://bibliotekanauki.pl/articles/1929740.pdf
Data publikacji:
1993-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.72.Ji
72.20.-i
71.45.-d
Opis:
The investigation of electrical conductivity, coefficient of thermal electromotive force, Hall coefficient, microhardness and mobility in Pb$\text{}_{1-x}$Ge$\text{}_{x}$Te (x = 0 ÷ 0.1) alloys in the temperature range of 77-300 K was carried out. Anomalies were detected in isotherms of properties in the vicinity of x = 0.008. The anomalies were treated as a manifestation of concentration phase transitions occurring in solid solutions of any kind and associated with existence of critical concentration (percolation threshold) at which the uninterrupted chain of interactions between impurity atoms is formed.
Źródło:
Acta Physica Polonica A; 1993, 84, 4; 729-732
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Controlling Mechanisms of Creep Deformation of New Air-Hardenable TiAl-Based Alloy
Autorzy:
Staneková, H.
Lapin, J.
Pelachová, T.
Powiązania:
https://bibliotekanauki.pl/articles/1418511.pdf
Data publikacji:
2012-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.72.-y
62.20.F-
62.40.+i
81.30.Mh
83.50.-v
Opis:
In the present work, controlling mechanisms of creep deformation of a new cast air-hardenable Ti-46Al-8Ta [at.%] alloy was studied. Long-term constant load tensile creep tests combined with an abrupt change of the applied stress were performed at 700°C. The response of the alloy to a stress reduction is analyzed. Transient behaviour with zero creep before recommencing creep at a reduced load is related to possible creep deformation mechanisms. The dislocation microstructures are analysed for creep strains corresponding to the minimum creep rate by transmission electron microscopy. The controlling mechanisms of creep deformation are identified from the transient creep behaviour of the alloy during stress reduction, the stress exponent and dislocation microstructures observed after creep testing.
Źródło:
Acta Physica Polonica A; 2012, 122, 3; 512-515
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Correlation between the band-gap energy and the electrical conductivity in MPr₂W₂O₁₀ tungstates (where M = Cd, Co, Mn)
Autorzy:
Sawicki, B.
Tomaszewicz, E.
Piątkowska, M.
Groń, T.
Duda, H.
Górny, K.
Powiązania:
https://bibliotekanauki.pl/articles/1160256.pdf
Data publikacji:
2016-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.20.Ci
72.20.-i
72.80.Sk
Opis:
The values of the direct allowed energy gap determined from the UV-vis-NIR measurements and Kubelka-Munk transformation decrease from 3.38 via 2.70 to 2.42 eV for MPr₂W₂O₁₀ in the sequence M = Cd, Co, Mn, while the values of the activation energy increase from 0.11 via 0.44 to 0.47 eV in the same sequence. In other words, the higher the activation energy, the smaller the energy gap. Because the energy gap is typical for insulators, so electron transport phenomena are considered under the Poole-Frenkel effect and small-polaron mechanism.
Źródło:
Acta Physica Polonica A; 2016, 129, 1a; A-94-A-96
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:
Deep Traps Distribution in $TlInS_2$ Layered Crystals
Autorzy:
Isik, M.
Gasanly, N.
Ozkan, H.
Powiązania:
https://bibliotekanauki.pl/articles/1808125.pdf
Data publikacji:
2009-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.55.-i
72.20.Jv
72.80.Jc
Opis:
The trap centers and distributions in $TlInS_2$ were studied in the temperature range of 100-300 K by using thermally stimulated currents technique. Experimental evidence was found for the presence of three trapping centers with activation energies 400, 570, and 650 meV. Their capture cross-sections were determined as 6.3 × $10^{-16}$, 2.7× $10^{-12}$, and 1.8× $10^{-11} cm^{2}$, respectively. It was concluded that in these centers retrapping is negligible as confirmed by the good agreement between the experimental results and the theoretical predictions of the model that assumes slow retrapping. An exponential distribution of hole traps was revealed from the analysis of the thermally stimulated current data obtained at different light excitation temperatures. This experimental technique provided a value of 800 meV/decade for the trap distribution.
Źródło:
Acta Physica Polonica A; 2009, 115, 3; 732-737
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Dose Dependences of the Conductivity and Luminescence in ZnSe Single Crystals
Autorzy:
Degoda, V.
Alizadeh, M.
Martynyuk, N.
Pavlova, N.
Powiązania:
https://bibliotekanauki.pl/articles/1030889.pdf
Data publikacji:
2018-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.20.-i
78.55.Et
29.40.Mc
Opis:
The studies of time-resolved dose dependences of conductivity and luminescence in ZnSe crystals at various temperatures (8, 85, 295, and 430 K) under X-ray and UV-excitation have revealed that dose dependences under X-ray excitation build up much more slowly and are more informative in comparison with UV-excitation. It is due to high penetrating depth of X-ray radiation and respective involvement of a large sample volume in the kinetic processes. Also, due to the local inhomogeneity of the excitation in the absorption of X-quantum, a significant share of the generated electron-hole pairs recombine in this local area creating a scintillation pulse, and not participating in the conductivity. The delay in the onset of the X-ray conductivity buildup at 8 K for several seconds is due to the high efficiency of the localization of free carriers in the traps, all of which become deep at this temperature. The different buildups of various bands of luminescence of irradiation time can be explained by not only different concentration of luminescence centers but also by their localization in various sections of free charge carriers. Dose dependences of the luminescence and conductivity also show that the scintillation pulse amplitudes and the current pulse amplitudes of the X-ray conductivity are not constant during irradiation of the ZnSe crystals.
Źródło:
Acta Physica Polonica A; 2018, 133, 4; 984-989
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
DX Puzzle: Where Are We Now?
Autorzy:
Wilamowski, Z.
Suski, T.
Jantsch, W.
Powiązania:
https://bibliotekanauki.pl/articles/1920958.pdf
Data publikacji:
1992-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.20.Jv
71.55.-i
Opis:
A brief review of the experimental data on the metastable DX-centers in AlGaAs is presented. The experimental proofs of the two-electron nature and of the intermediate, one-electron state of the DX-centers are discussed. We collect the available experimental data on the ground state, electron-emission and capture energies and we discuss the nature of the lattice barrier. The effect of splitting of these energies in AlGaAs alloys and the consequences of the splitting on the capture and emission kinetics are analyzed. The different character of the barrier and of the alloy splitting for donors of the IV and VI group is underlined. The necessity to consider the interdonor Coulomb interaction when discussing the experimental data is also pointed out.
Źródło:
Acta Physica Polonica A; 1992, 82, 4; 561-571
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of Annealing on the AC Conductivity and the Dielectric Properties of In$\text{}_{2}$Te$\text{}_{3}$ Thin Films
Autorzy:
Afifi, M. A.
Abd El-Wahabb, E.
Bekheet, A. E.
Atyia, H. E.
Powiązania:
https://bibliotekanauki.pl/articles/2014347.pdf
Data publikacji:
2000-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
77.55.+f
72.20.-i
Opis:
In$\text{}_{2}$Te$\text{}_{3}$ thin films were prepared by thermal evaporation technique. The composition of the films is checked by energy dispersive X-ray analysis. X-ray analysis showed that the as-deposited In$\text{}_{2}$Te$\text{}_{3}$ films as well as films annealed at temperatures ≤473K have crystalline structure. The ac conductivity σ$\text{}_{ac}$(ω), the dielectric constant ε$\text{}_{1}$ and the dielectric loss ε$\text{}_{2}$ of In$\text{}_{2}$Te$\text{}_{3}$ films were studied in the temperature range 303-373K and in the frequency range 100Hz-100kHz. The ac conduction activation energy ΔE$\text{}_{σ}$(ω) was found to be 0.065eV for the as-deposited films. The ac conductivity was found to obey the relation σ$\text{}_{ac}$(ω)=Aω$\text{}^{s}$, where s is the frequency exponent. The obtained temperature dependence of s is reasonably interpreted by quantum mechanical tunneling model. Both the dielectric constant ε$\text{}_{1}$ and the dielectric loss ε$\text{}_{2}$ increased with temperature and decreased with frequency in the investigated range. The frequency and temperature dependencies of σ$\text{}_{ac}$(ω), ε$\text{}_{1}$, and ε$\text{}_{2}$ for the annealed samples have the same behavior as that for the as-deposited samples. However, values of σ$\text{}_{ac}$(ω), ε$\text{}_{1}$, and ε$\text{}_{2}$ measured at any frequency and temperature increased with annealing temperature up to 473K. It was found also that ΔE$\text{}_{σ}$(ω) decreased with annealing temperature.
Źródło:
Acta Physica Polonica A; 2000, 98, 4; 401-409
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of Deep-Level Defects on Transient Photoconductivity of Semi-Insulating 4H-SiC
Autorzy:
Suproniuk, M.
Kamiński, P.
Kozłowski, R.
Pawłowski, M.
Powiązania:
https://bibliotekanauki.pl/articles/1364028.pdf
Data publikacji:
2014-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.40.+w
71.55.-i
72.20.-i
Opis:
A model enabling the equilibrium conductivity and transient photoconductivity of semi-insulating 4H-SiC to be simulated has been demonstrated. Using this model, the simulations of both equilibrium conductivity and transient photoconductivity have been carried out. Both the simulation and experimental results have shown that the evolution of photoconductivity in time after switching on the band-to-band generation of electron-hole pairs is strongly affected by the properties of deep level defects. The results of transient photocurrent measurements confirm the simulations results indicating that the $Z_{1/2}$ center is a very effective recombination center in semi-insulating 4H-SiC having detrimental effect on the transient photoconductivity.
Źródło:
Acta Physica Polonica A; 2014, 125, 4; 1042-1048
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Efficient Terahertz Emission from InGaN/GaN Heterostructure
Autorzy:
Reklaitis, A.
Powiązania:
https://bibliotekanauki.pl/articles/1505710.pdf
Data publikacji:
2011-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
42.72.Ai
73.20.Mf
75.70.-i
78.20.Bh
78.47.-p
Opis:
Terahertz emission from the freestanding InGaN/GaN heterostructure illuminated by femtosecond optical pulse is considered using Monte Carlo simulations. The results of Monte Carlo simulations show that the power of terahertz emission from InGaN/GaN heterostructure exceeds the power of the emission from InN surface by one order of magnitude.
Źródło:
Acta Physica Polonica A; 2011, 119, 2; 212-214
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electrical and Dielectric Properties of Amorphous Ge$\text{}_{1}$Se$\text{}_{1.35}$TL$\text{}_{0.1}$ Films
Autorzy:
Abdel-Aziz, M. M.
Afifi, M. A.
Labib, H. H.
El-Metwally, E. G.
Powiązania:
https://bibliotekanauki.pl/articles/2014346.pdf
Data publikacji:
2000-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.80.Ng
72.20.-i
Opis:
The temperature dependence of the DC and AC electrical conductivity were measured for Ge$\text{}_{1}$Se$\text{}_{1.35}$Tl$\text{}_{0.1}$ films. The value of DC electrical conduction energy ΔE$\text{}_{σ}$ does not depend on film thickness in the investigated range with mean value of 0.72eV. The AC conductivity σ$\text{}_{AC}$ is related to frequency by the expression σ$\text{}_{AC}$=Aω$\text{}^{S}$, where S is the frequency exponent which decreases linearly with increasing temperature. This can be explained in terms of the pair (bipolaron) correlated barrier hopping model suggested by Elliott. The frequency and temperature dependence of real and imaginary parts of the dielectric constant were studied for Ge$\text{}_{1}$Se$\text{}_{1.35}$Tl$\text{}_{0.1}$ films. The dielectric constant (real part) and the dielectric loss (imaginary part) increase with increasing temperature and decrease with increasing frequency in the investigated range of frequency and temperature. The maximum barrier height W$\text{}_{M}$ can be calculated according to the Giuntini equation at different temperatures. The obtained value of W$\text{}_{M}$ is in good agreement with the theory of hopping of charge carriers over a potential barrier as suggested by Elliott in case of chalcogenide glasses.
Źródło:
Acta Physica Polonica A; 2000, 98, 4; 393-399
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 65

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