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Wyświetlanie 1-15 z 65
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:
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:
Infrared active phonons and optical band gap in multiferroic GdMnO₃ studied by infrared and UV-visible spectroscopy
Autorzy:
Bukhari, S.
Ahmad, J.
Powiązania:
https://bibliotekanauki.pl/articles/1075504.pdf
Data publikacji:
2016-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
63.20.-e
78.20.-e
72.20.-i
73.20.Mf
Opis:
Optical properties of multiferroic GdMnO₃ synthesized by sol-gel method have been investigated by measuring the infrared reflectivity and UV-visible absorption spectra. The infrared reflectivity spectrum of polycrystalline GdMnO₃ in the frequency range 30-7500 cm^{-1} at room temperature contains several phonon modes. The resonant frequency of observed infrared active phonon modes is found comparable with theoretically predicted results. Mean Born effective charges are calculated and discussed in view of the origin of ferroelectricity in GdMnO₃. Three strong absorption peaks observed in the UV-visible spectrum are attributed to the Mn (3d)-electron transitions. The optical band gap ≈1.2 eV is estimated from UV-visible absorption spectrum using Tauc's relation. GdMnO₃ seems to behave like an indirect gap semiconductor.
Źródło:
Acta Physica Polonica A; 2016, 129, 1; 43-48
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Semi-conducting properties of titanium dioxide layer on surface of Ti-15Mo implant alloy in biological milieu
Autorzy:
Szklarska, M.
Dercz, G.
Kubisztal, J.
Balin, K.
Łosiewicz, B.
Powiązania:
https://bibliotekanauki.pl/articles/1152668.pdf
Data publikacji:
2016-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
87.85.jj
82.45.Bb
72.20.-i
Opis:
The object of this work was to investigate structure, electrochemical behavior and semiconducting properties of the TiO₂ oxide layer on the Ti-15Mo implant alloy surface in normal and inflammatory conditions of physiological saline solution. X-ray photoelectron spectroscopy measurements confirm the presence of the oxide layer on the Ti-15Mo alloy surface. Electrochemical studies indicate excellent corrosion resistance of Ti-15Mo alloy in physiological saline solution. It was found that the investigated material under normal and inflammatory conditions behave like an insulator and n-type semiconductor, respectively.
Źródło:
Acta Physica Polonica A; 2016, 130, 4; 1085-1087
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electrical and Optical Characteristics of $n-GaSb//n-GaIn_{0.24}AsSb//p-GaAl_{0.34}AsSb$ Heterostructure Photodiode
Autorzy:
Ahmetoglu, M.
Kucur, B.
Andreev, I.
Kunitsyna, E.
Mikhailova, M.
Yakovlev, Y.
Powiązania:
https://bibliotekanauki.pl/articles/1401231.pdf
Data publikacji:
2015-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.20.-i
73.40.Kp
72.40.+w
Opis:
In the present paper, electrical and optical properties of $n-GaSb//n-GaIn_{0.24}AsSb//p-GaAl_{0.34}AsSb$ double heterostructure (DH) with a diameter of 0.3 mm are reported. The current-voltage (I-V) characteristics of the structure were investigated at several temperatures in both, dark and under the illumination conditions. The effect of illumination was studied at different intensity values. Short circuit current and open circuit voltage as a function of intensity of incident light in photovoltaic mode are investigated.
Źródło:
Acta Physica Polonica A; 2015, 127, 4; 1007-1009
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electronic Band Structures of $La_{2/3}Pb_{1/3}Mn_{2/3}(Fe,Co,Ni)_{1/3}O_{3}$
Autorzy:
Kowalik, M.
Tokarz, W.
Kołodziejczyk, A.
Powiązania:
https://bibliotekanauki.pl/articles/1385092.pdf
Data publikacji:
2015-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.20.-b
71.55.Ak
72.80.Ga
75.47.Lx
79.60.-i
Opis:
We present calculations of the electronic band structures of $La_{2/3}Pb_{1/3}Mn_{2/3}(Fe,Co,Ni)_{1/3}O_{3}$ colossal magneto-resistance manganites. The calculations are based on first-principles density functional theory with general gradient approximation GGA+U using WIEN2k package. The calculations show that electronic structures of these compounds consist mainly of Mn 3d, O 2p, and (Fe,Co,Ni) 3d states, which are hybridized over whole valence bands. Substitution Mn ion by Fe, Co, or Ni ions reduces the Mn and O contributions to the valence bands and weakens the double exchange interaction. The results are in good agreement with available experimental data.
Źródło:
Acta Physica Polonica A; 2015, 127, 2; 251-253
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Study of the Diffused Reflectance and Microstructure for the Phase Transformation of $KNO_{3}$
Autorzy:
Hafez, M.
Yahia, I.
Taha, S.
Powiązania:
https://bibliotekanauki.pl/articles/1398861.pdf
Data publikacji:
2015-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.05.cp
64.60.-i
61.43.Gt
78.20.-e
72.15.Eb
Opis:
Optical, micro-structural, thermal and electrical properties of the investigated potassium nitrate ($KNO_{3}$) samples were characterized by various techniques such as X-ray analysis, scanning electron microscopy, UV-VIS-NIR absorption and differential scanning calorimetry. The presence of structural phase transition is checked by differential scanning calorimetry, electrical and X-ray analysis measurement. The thermal energy required for such transformation is calculated and found to be 46.2 J/g. The activation energies of the electrical conduction for $KNO_{3}$ were found to be 0.236 eV for phase II and 0.967 eV for phase I. The optical band gaps of $KNO_{3}$ for the higher photon energy are calculated and equal to 5.03 and 5.01 eV for II and I phases, respectively and at lower photon energy, the values are equal to 3.84 and 3.80 eV for II and I phases, respectively. The data which leads to the interpretation of electronic spectra of potassium nitrate is possible to assume that the long wavelength part of absorption band corresponds to n-π* transition. Then, the short-wavelength part is probably due to the transition in a higher excited state of symmetry π-π*. The mean values of crystalline sizes are determined by scanning electron microscopy analysis. Such information can considerably aid in understanding the process of transformations near the phase crystal modifications at 129°C.
Źródło:
Acta Physica Polonica A; 2015, 127, 3; 734-740
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Synthesis, Roentgenophase Analysis and Physical Properties of $TlIn_{1-x}Er_xSe_2$ Solid Solutions
Autorzy:
Mustafaeva, S.
Kerimova, E.
Gasanov, A.
Powiązania:
https://bibliotekanauki.pl/articles/1402129.pdf
Data publikacji:
2015-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.20.Eh
71.20.-b
71.20.Nr
71.55.-i
72.15.Eb
72.15.Rn
72.20.-i
72.20.Ee
72.20.Jv
72.30.+q
Opis:
The results of high-frequency dielectric measurements on obtained $TlIn_{1-x}Er_xSe_2$ single crystals provided an opportunity to determine the mechanisms of dielectric losses and charge transport, and also to evaluate the density of states at the Fermi level; the average time of charge carrier hopping between localized states, average hopping distance, scattering of trap states near the Fermi level; concentration of deep traps.
Źródło:
Acta Physica Polonica A; 2015, 128, 4; 697-699
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:
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:
Electronic Band Structure and Photoemission States of $Bi_{1.96}Mg_{0.04}Se_3$
Autorzy:
Tokarz, W.
Zalecki, R.
Kowalik, M.
Kołodziejczyk, A.
Kozłowski, A.
Miotkowski, J.
Powiązania:
https://bibliotekanauki.pl/articles/1374118.pdf
Data publikacji:
2014-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.20.-b
71.55.Ak
72.80.Ga
75.47.Lx
79.60.-i
Opis:
We present theoretical band structure calculations and ultraviolet electron photoemission spectroscopy of a topological insulator $Bi_{1.96}Mg_{0.04}Se_3$. Our calculations were based on the first-principles density functional theory with general gradient approximation using Wien2k package with the spin-orbit interaction included by a second-variation method. The R3̅m crystal structure was optimized. In consequence, 4% decrease of volume and 3% decrease of ratio c/a was obtained. This modified structure was multiplied three times in a and b direction in order to place proper amount of Mg. Final crystal structure P3m1 with 135 atoms was used for the calculations. As a result metallic band structure was obtained with conduction band extended from -5.6 eV up to 0.16 eV. It composes mostly from Se p states. Comparison of total DOS with ultraviolet photoemission spectrum shows similar features.
Źródło:
Acta Physica Polonica A; 2014, 126, 4a; A-127-A-129
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Investigation on the Mechanisms of Nitrogen Shallow Implantation Influence on Trap Properties of $SiO_2$/n-Type 4H-SiC Interface
Autorzy:
Król, K.
Sochacki, M.
Szmidt, J.
Powiązania:
https://bibliotekanauki.pl/articles/1363825.pdf
Data publikacji:
2014-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.40.Qv
68.55.ag
72.20.-i
72.25.-b
Opis:
Silicon carbide (SiC) is the only wide-bandgap semiconductor capable of forming native dielectric layer of $SiO_2$ by thermal oxidation. This unique property of SiC combined with its high thermal conductivity and high critical field makes this semiconductor material suitable for high power electronic devices. Unfortunately, the state-of-the art technology does not use the full benefits of the material, especially in the case of MOSFET transistors. This is caused by insufficient electrical parameters of $SiO_2$/SiC interface. Two-component structure of the material and its high density result in high level of interface traps reducing the surface mobility and thus increasing series resistance of the device. One of the proposed methods of reducing the trap density in SiC MOS structure is a shallow nitrogen implantation prior to oxidation. This technique is based on the observation that introducing nitrogen into the $SiO_2$/SiC system results in significant reduction of trap states density and increase of the channel effective mobility. The shallow implantation technique has been reported to be as much effective as nitric oxide annealing which is one of the most effective techniques for oxide quality improvement in case of SiC. Unlike the diffusion based techniques, like postoxidation annealing, implantation of the nitrogen prior oxidation has the possibility of nitrogen concentration control near the oxide interface during oxidation process itself. This property is important since it was shown that the improvement degree is directly proportional to amount of nitrogen built in the vicinity of $SiO_2$/SiC interface during oxidation. However, previous investigations about this technique were inconclusive about the influence of implantation parameters and process conditions on observed effects. Both improvement and deterioration of interface quality was observed by different researchers. This behavior was never explained clearly. The primary objective of this research is to analyze the impact of implantation conditions on electrical properties of $SiO_2$/SiC MOS structure. This analysis is used to evaluate a hypothetical description of physical phenomena during oxidation of shallowly implanted substrates.
Źródło:
Acta Physica Polonica A; 2014, 125, 4; 1033-1037
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Shielding Effectiveness of Ceramic Bodies Produced with Natural Zeolite
Autorzy:
Kanberoğlu, B.
Şükran Demirkıran, A.
Powiązania:
https://bibliotekanauki.pl/articles/1182903.pdf
Data publikacji:
2014-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.05.Je
07.50.Hp
13.40.-f
72.20.-i
Opis:
In this study, electromagnetic shielding effectiveness of ceramic bodies produced with natural zeolite illuminated by an electromagnetic pulse is investigated. A matrix model is used to calculate the propagation of electromagnetic pulse through sample. Shielding effectiveness of sample is determined for both transmitted electric and magnetic fields. Mathematical theory of the interaction and the shielding effectiveness of the sample is determined as a function of frequency, thickness of the material and the incidence angle of electromagnetic pulse. Zeolites used in this study were supplied from ETI Holding Company located in Turkey. Water was added as a binder and disc samples were shaped by uniaxial dry pressing at pressing pressure of 1.5 tone. Samples were fired in an electric furnace with a heating rate of 10°C/min at 1150C with a period of 60 min. Electrical measurements are performed to determine the dielectric constant and dielectric loss tangent at 25C constant temperature between frequency range from 1 kHz up to 2 MHz.
Źródło:
Acta Physica Polonica A; 2014, 125, 2; 642-644
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electron Dynamics in Crystalline Semiconductors
Autorzy:
Zawadzki, W.
Powiązania:
https://bibliotekanauki.pl/articles/1400405.pdf
Data publikacji:
2013-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.28.+d
73.61.Ey
72.20.-i
Opis:
Electron dynamics in crystalline semiconductors is described by distinguishing between an instantaneous velocity related to electron's momentum and an average velocity related to its quasi-momentum in a periodic potential. It is shown that the electron velocity used in the theory of electron transport and free-carrier optics is the average electron velocity, not the instantaneous velocity. An effective mass of charge carriers in solids is considered and it is demonstrated that, in contrast to the "acceleration" mass introduced in textbooks, it is a "velocity" mass relating carrier velocity to its quasi-momentum that is a much more useful physical quantity. Among other advantages, the velocity mass is a scalar for spherical but nonparabolic energy bands ϵ(k), whereas the acceleration mass is not a scalar. Important applications of the velocity mass are indicated. A two-band k·p^ model is introduced as the simplest example of a band structure that still keeps track of the periodic lattice potential. It is remarked that the two-band model, adequately describing narrow-gap semiconductors (including zero-gap graphene), strongly resembles the special theory of relativity. Instructive examples of the "semi-relativistic" analogy are given. The presentation has both scientific and pedagogical aspects.
Źródło:
Acta Physica Polonica A; 2013, 123, 1; 132-138
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
La-doped and La/Mn-co-doped Barium Titanate Ceramics
Autorzy:
Vijatović Petrović, M.
Bobić, J.
Grigalaitis, R.
Stojanović, B.
Banys, J.
Powiązania:
https://bibliotekanauki.pl/articles/1400499.pdf
Data publikacji:
2013-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.20.Ka
81.40.Ef
77.80.B-
72.20.-i
84.37.+q
Opis:
Barium titanate ceramics doped with 0.3 mol.% lanthanum and co-doped with 0.3 mol.% lanthanum and 0.05 mol.% manganese were investigated. The powders were prepared by a modified polymeric precursor method based on the Pechini process. The ceramics were obtained by sintering at 1300C for 8 h. The influence of dopants on structural changes and grain size reduction was analyzed. The presence of dopants influenced the tetragonality of the barium titanate crystal structure. Reduction of polygonal grain size with dopant addition was noticed. In the doped ceramics, characteristic phase transitions were shifted to lower temperatures in comparison with pure barium titanate. The dielectric permittivity value showed the tendency of a slight increase with lanthanum addition and further increase with adding of manganese. La as a single dopant increased the diffuseness of phase transitions indicating the formation of a diffuse ferroelectric material but in the co-doped ceramics the phase transition diffuseness decreased. The resistivity of the co-doped ceramics was higher than for lanthanum doped ceramics, indicating possible segregation of manganese at grain boundaries that influenced the total resistivity of the material.
Źródło:
Acta Physica Polonica A; 2013, 124, 1; 155-160
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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