Full-text resources of PSJD and other databases are now available in the new Library of Science.
Visit https://bibliotekanauki.pl
Preferences help
Polish version English version Language
enabled [disable] Abstract
Number of results

Results found: 13

Number of results on page
first rewind previous Page / 1 next fast forward last

Search results

Search:
in the keywords:  72.20.Ee
help Sort By:

help Limit search:
first rewind previous Page / 1 next fast forward last
1
Content available remote

Low-Temperature DC Carrier Transport in (Co_{0.45}Fe_{0.45}Zr_{0.10})_{x}(Al_2O_3)_{1-x} Nanocomposites Sputtered in Mixed Argon-Oxygen Atmosphere

100%
Svito I., Fedotov A., Saad A., Koltunowicz T., Zukowski P., Bury P.
|
|
vol. 125
|
issue 6
1351-1355
EN
This paper studies the temperature dependences (2 < T < 300 K) of the DC conductivity σ(T) for the (Co_{0.45}Fe_{0.45}Zr_{0.10})_x(Al_2O_3)_{1-x} nanocomposites (30 < x < 65 at.%) sputtered in Ar + O_2 atmosphere. It is shown that at temperatures lower than 100-150 K dependences of DC conductance on temperature for all the studied samples are due to the Shklovski-Efros variable range hopping mechanism. It was also observed that σ(x,T) dependences can be attributed to the formation of FeCo-based oxide "shells" around metallic alloy nanoparticles due to incorporation of oxygen in the vacuum chamber during the deposition procedure.
2
Publication available in full text mode
Content available

Mn Impurity in Bulk GaAs Crystals

100%
Pawłowski M., Piersa M., Wołoś A., Palczewska M., Strzelecka G., Hruban A., Gosk J., Kamińska M., Twardowski A.
Acta Physica Polonica A
|
2005
|
vol. 108
|
issue 5
825-830
EN
Magnetic and electron transport properties of GaAs:Mn crystals grown by Czochralski method were studied. Electron spin resonance showed the presence of Mn acceptor A in two charge states: singly ionized A^- in the form of Mn^{2+}(d^5), and neutral A^0 in the form of Mn^{2+}(d^5) plus a bound hole (h). It was possible to determine the relative concentration of both types of centers from intensity of the corresponding electron spin resonance lines. Magnetization measured as a function of magnetic field (up to 6 T) in the temperature range of 2-300 K revealed overall paramagnetic behavior of the samples. Effective spin was found to be about 1.5 value, which was consistent with the presence of two types of Mn configurations. In most of the studied samples the dominance of Mn^{2+}(d^5)+h configuration was established and it increased after annealing of native donors. The total value of Mn content was obtained from fitting of magnetization curves with the use of parameters obtained from electron spin resonance. In electron transport, two mechanisms of conductivity were observed: valence band transport dominated above 70 K, and hopping conductivity within Mn impurity band at lower temperatures. From the analysis of the hopping conductivity and using the obtained values of the total Mn content, the effective radius of Mn acceptor in GaAs was estimated as a = 11±3Å.
3
Content available remote

Electrical Resistivity of CrN Thin Films

100%
Batko I., Batkova M., Lofaj F.
|
|
vol. 126
|
issue 1
415-416
EN
The work is focused on the measurements of electrical resistivity of CrN thin films deposited on glass substrates by DC-magnetron sputtering in Ar+N_{2} atmosphere. The studied samples reveal semiconducting behaviour of electrical resistivity in the whole range of tested preparation parameters (such as pressure and composition of Ar-N_{2} mixture), whereas the electrical transport regime is strongly influenced by parameters of preparation. Numerical analysis of the experimental data showed that electrical transport can be adequately described in terms of variable-range hopping conduction in selected temperature intervals. Moreover, S-shaped anomaly in ρ(T) dependence, being expected to be a consequence of phase transition to a low-temperature antiferromagnetic orthorhombic phase, has been observed for sample with the highest concentration of N_{2} in the temperature interval of 220-250 K. The obtained results indicate that technology processes typically used for preparation of CrN coatings represent a promising potential to develop also high sensitivity cryogenic sensors for high magnetic fields applications.
4
Content available remote

Morphology, Optical and AC Electrical Properties of Copper Phthalocyanine Thin Films

100%
Azim-Araghi M., Haji Mirza Mohamadi S., Bisadi Z.
|
|
vol. 125
|
issue 1
87-92
EN
AC electrical properties of sandwich devices composed of thermally evaporated thin films of copper phthalocyanine (CuPc) with aluminum and gold electrodes (Al/CuPc/Au) are investigated over frequency (f) range of 10^2 - 10^5 Hz and temperature range of 293-453 K. Morphology of the samples was studied via field emission scanning electron microscope images and X-ray diffraction micrographs. The X-ray diffraction micrograph indicates the configuration of α-CuPc with the (510) plane as the preferred orientation. UV-Vis absorption spectrum was analyzed and the optical band-gap energy of CuPc thin film was determined to be 2.81 ± 0.01 eV. Capacitance increased with increasing temperature especially for f = 10^2 Hz. Loss factor decreased considerably with increasing frequency to a minimum value at about f = 10^4 Hz and increased afterwards. Capacitance is generally independent of frequency for T ≤ 413 K; however it decreases remarkably with increasing frequency for T > 413 K. The conductivity increases quite noticeably with increasing frequency particularly for T ≤ 413 K. The AC electrical characteristics are in good agreement with Goswami and Goswami model. According to our data, at high temperatures, the band theory is applicable in describing the conduction process, whereas hopping mechanism is dominant at low temperatures.
5
Content available remote

Current-Driven Monte Carlo Simulation of Conduction in Switching Chalcogenides

100%
Piccinini E., Buscemi F.
Acta Physica Polonica A
|
2011
|
vol. 119
|
issue 2
121-124
EN
The I(V) characteristics of amorphous chalcogenides usually show a negative differential conductance region, which makes the material switch from a high-resistive to a high-conductive state. This feature is of the utmost importance for adopting these materials in the manufacturing of solid-state memory devices. We propose here two complementary models for the interpretation of the switching mechanism, both stemming from and updating the literature analysis. The former is based on macroscopic equations that can be solved analytically; the latter is a current-driven three-dimensional Monte Carlo simulation of the device. A critical analysis of the two models is also performed in order to identify the fundamental conditions accounting for the voltage snap-back of the I(V) curve.
6
Content available remote

The Electrical Properties of Some Composite Materials Based on Sodium and Tantalum Oxides

100%
Malaescu D., Grozescu I., Sfirloaga P., Vlazan P., Marin C.
Acta Physica Polonica A
|
2016
|
vol. 129
|
issue 1
133-137
EN
Two samples of Na-Ta oxides were synthesized by the hydrothermal method at reaction temperatures of 160°C (sample A) and 200°C (sample B). For reference, a third sample of pure NaTaO₃ was prepared by the sol-gel method (sample C). Using X-ray diffraction, scanning electron microscopy, UV-vis diffuse reflectance spectra and electric measurements, structural, morphologic, spectroscopic and electric properties of samples were investigated. The structural characterization by X-ray diffraction revealed that samples A and B are mixtures of Na-Ta oxides (including NaTaO₃ and other compounds), whilst sample C is pure NaTaO₃. UV-vis diffuse reflectance spectra allowed evaluation of the band gap energy (E_{g}), resulting in 3.88 eV for sample A, 3.93 eV for sample B and 4.1 eV for sample C. Electrical resistivity measurements, over the temperature range 300-450 K, showed a typical semiconductor behavior of the investigated samples, with the effective activation energy, E_{a} of 0.47 eV (sample A), 0.45 eV (sample B) and 0.82 eV (sample C). Based on the Mott variable range hopping model, the conductivity mechanism in the investigated samples was analyzed. The results shown that the density of states at the Fermi-level, N(E_{F}) is constant in the investigated temperature range and the typical values of N(E_{F}) are 0.713 × 10^{18} eV^{-1} cm^{-3} (sample A), 0.621 × 10^{18} eV^{-1} cm^{-3} (sample B) and 0.855 × 10^{17} eV^{-1} cm^{-3} (sample C). Other parameters of VRH model such as the hopping distance R and the hopping energy W have also been computed and the following values at the room temperature were obtained: R=15.7 nm and W=86 meV (for sample A); R=16.3 nm and W=89 meV (for sample B) and R=26.7 nm and W=147 meV (for sample C).
7
Publication available in full text mode
Content available

Structure and Transport Properties of La_{0.75-x}RE_xCa_{0.25}MnO_3 (RE = Gd, Dy, Ho; 0≤ x≤0.75) Manganites

100%
Drozd V., Pękała M., Kovac J., Skorvanek I., Szymański M., Nedilko S.
Acta Physica Polonica A
|
2004
|
vol. 106
|
issue 5
751-758
EN
Structure and transport properties have been studied for a series of La_{0.75-x}RE_xCa_{0.25}MnO_3 manganites with heavy rare earth ions of Gd, Dy, Ho substituting La with x=0, 0.10, 0.25, 0.50, and 0.75. Polycrystalline samples were prepared by the carbonate precipitation route. The oxygen content was determined by the iodometric titration. The X-ray investigations carried out by the powder method show that the unit cell volume gradually decreases and orthorhombic distortion of the lattice increases with rising RE content. Below the room temperature the electrical resistivity is of the semiconducting type for all the samples studied. Electrical resistivity vs. temperature dependences were analyzed within different models: simple thermal activation, Mott's variable range hopping, adiabatic, nonadiabatic, and bipolaron. The Curie temperatures of Gd, Dy, and Ho substituted manganites determined from magnetization measurements show that at 280 K all the samples are in the paramagnetic phase. The increasing RE fraction reduces magnetization at 4 K as compared to La_{0.75}Ca_{0.25}MnO_3.
8
Publication available in full text mode
Content available

Formation of Mn-Related Defect Band in InP

100%
Macieja B., Korona K., Piersa M., Witowski A., Wasik D., Wysmołek A., Strzelecka G., Hruban A., Surma B., Palczewska M., Kamińska M., Twardowski A.
|
EN
Electron paramagnetic resonance, optical absorption, luminescence and electrical studies of InP highly doped with Mn were performed. Electron paramagnetic resonance revealed presence of manganese in Mn^{2+}(d^5) configuration. In optical absorption, systematic reduction of InP band gap was observed with increase in Mn content. This was correlated with increase in photoionization-type absorption band starting at 0.2 eV. Time-resolved photoluminescence measurements showed decrease in photoexcited carrier lifetime and shortening of donor-acceptor pair recombination time with increase in Mn content. Moreover, photoluminescence band was shifted to lower energies, similarly to optical band gap. In electrical transport two mechanisms of conductivity were observed. Valence band transport dominated at higher temperatures, above 160 K, and activation energy of free-hole concentration was determined as about 0.20 eV. At lower temperatures hopping conductivity, clearly related to Mn defect band, was present. All these results were consistent with assumption of creation of Mn-related defect-band at 0.2 eV above InP valence band. It was found that Mn centers responsible for this band were in configurations of either d^5 or d^5 plus a hole localized about 7Å around corresponding Mn core.
9
Content available remote

The Features of Real Part of Admittance in the Nanocomposites (Fe_{45}Co_{45}Zr_{10})_{x}(Al_2O_3)_{100 - x} Manufactured by the Ion-Beam Sputtering Technique with Ar Ions

100%
Kołtunowicz T., Zhukowski P., Fedotova V., Saad A., Larkin A., Fedotov A.
Acta Physica Polonica A
|
2011
|
vol. 120
|
issue 1
35-38
EN
The temperature and frequency dependences of the admittance real part σ (T, f) in granular (Fe_{45}Co_{45}Zr_{10})_{x}(Al_2O_3)_{100 - x} nanocomposite films around the percolation threshold x_{C} were investigated. The behaviour of σ (T, f) vs. the temperature and frequency over the ranges 77-300 K and 50 Hz-1 MHz, respectively, displays the predominance of an activation (hopping) conductance mechanism for the samples below the percolation threshold x_{C} and of a metallic one beyond the x_{C} determined as 54 ± 2 at.%. The mean hopping range d for the nanoparticles diameter D was estimated at different metallic phase content x.
10
Content available remote

Hopping Conductance in Nanocomposites (Fe_{0.45}Co_{0.45}Zr_{0.10})_{x}(Al_2O_3)_{1 - x} Manufactured by Ion-Beam Sputtering of Complex Target in Ar+O_2 Ambient Gas

100%
Kołtunowicz T., Zhukowski P., Fedotova V., Saad A., Fedotov A.
Acta Physica Polonica A
|
2011
|
vol. 120
|
issue 1
39-42
EN
We report the investigation of a real part of the admittance σ of granular nanocomposites (Fe_{0.45}Co_{0.45}Zr_{0.10})_{x}(Al_2O_3)_{1 - x} with 0.30 < x < 0.70 in the dielectric (hopping) regime. An analysis of the σ(T, f, x) dependences in the as-deposited and annealed films over the temperature 77 K < T < 300 K and frequency 50 < f < 10^6 Hz ranges displayed the predominance of an activation (hopping) conductance mechanism with dσ/ dT > 0 for the samples below the percolation threshold x_{C} ≈ 0.76 ± 0.05. Based on the earlier models for hopping AC conductance, computer simulation of the frequency coefficient α_{f} of hopping conductance depending on the probability of jump p, frequency f, and also on the shape of σ(f) curve was performed. The experimental and simulation results revealed a good agreement.
11
Content available remote

Formation of Noncoil-Like Inductance in Nanocomposites (Fe_{0.45}Co_{0.45}Zr_{0.10})_{x}(Al_2O_3)_{1-x} Manufactured by Ion-Beam Sputtering of Complex Targets in Ar+O_2 Atmosphere

88%
Zhukowski P., Kołtunowicz T., Węgierek P., Fedotova J., Fedotov A., Larkin A.
Acta Physica Polonica A
|
2011
|
vol. 120
|
issue 1
43-45
EN
This paper investigates the inductive contribution to AC conductance in the granular nanocomposites (Fe_{0.45}Co_{0.45}Zr_{0.10})_{x}(Al_2O_3)_{1-x}. The initial nanocomposites studied were manufactured in Ar+O_2 atmosphere by ion-beam sputtering of the target containing Fe_{0.45}Co_{0.45}Zr_{0.10} and alumina stripes and then subjected to the annealing procedure in air over the temperature range 373 K < T_{a} < 873 K. These samples, before and after annealing, were studied using the temperature 77 K < T_{p} < 300 K and frequency 50 Hz < f < 1 MHz dependences of a real part of the admittance σ(T, f). Analysis of the observed σ (f, T_{p}) dependences for x < 0.5 demonstrated that in the studied samples the equivalent circuits with the capacitive and noncoil-like inductive contributions can be accomplished. Just in this case, the capacitive properties of RLC circuit with the phase angle - 90° ≤ θ_{L} < 0° are exhibited at low frequencies and the inductive properties with 0° ≤ θ_{H} < 90° become apparent at high frequencies. A value of the critical frequency f_{R}, where θ_{H} changes sign, depends on the metallic phase concentration x, measuring temperature T_{p}, and annealing temperature T_{a}.
12
Content available remote

Dielectric and Ac Conductivity Studies of Mn-Doped Na_{1.86}Li_{0.10}K_{0.04}Ti_3O_7 Ceramics

75%
Singh R., Shripal
|
|
vol. 125
|
issue 1
67-72
EN
Dielectric-spectroscopic and ac conductivity studies on 0.01 and 1.0 molar percentage manganese doped layered Na_{1.86}Li_{0.10}K_{0.04}Ti_3O_7 ceramics have been reported. The dependence of loss tangent (tan δ) and relative permittivity (ε_{r}) on temperature in the range 350-775 K and on frequency in the range 10 kHz-1 MHz have been undertaken. The losses are the characteristics of dipole mechanism, electrical conduction and space charge polarization. The obtained conductivity plots between log(σ_{ac}T) versus 1000/T have been divided into four regions namely region I, II, III, and IV. The mechanism of conduction in region I is acknowledged to electronic hopping conduction. The less frequency and more temperature dependent region II is ascribed as a mixed mechanism "associated interlayer ionic conduction, electron hopping, and alkali ion hopping conduction". The unassociated interlayer ionic conduction along with alkali ion hopping conduction mechanisms are contributing to the transport process in the mid temperature region III. The mechanism of conduction in the highest temperature region IV may be recognized as the modified interlayer ionic conduction. The conductivity versus frequency curves lead to conclude that the electronic hopping conduction diminishes with the rise of temperature.
13
Content available remote

Synthesis, Roentgenophase Analysis and Physical Properties of TlIn_{1-x}Er_xSe₂ Solid Solutions

63%
Mustafaeva S., Kerimova E., Gasanov A.
Acta Physica Polonica A
|
2015
|
vol. 128
|
issue 4
697-699
EN
The results of high-frequency dielectric measurements on obtained TlIn_{1-x}Er_xSe₂ 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.
first rewind previous Page / 1 next fast forward last
JavaScript is turned off in your web browser. Turn it on to take full advantage of this site, then refresh the page.