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  1. 30 Acta Physica Polonica A

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  1. 6 Fedotov A.

  2. 4 Saad A.

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  4. 3 Koltunowicz T.

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1
Content available remote

Hall Mobility Field Effect in Two Layer Conductivity Samples

100%
Mekys A., Storasta J., Zindulis A., Smilga A., Balakauskas S.
Acta Physica Polonica A
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2008
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vol. 114
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issue 4
903-912
EN
Classical Hall mobility experimental setup was applied for samples with parallel plane (sandwich) variable conductivity layers. The measured effective Hall mobility strongly depends on applied electric field and does not characterise the real carrier mobility. Numerical modelling explains the effect as a consequence of electric field redistribution and lowering at Hall contacts. Measurement of carrier mobility in such structures is suggested.
2
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Impedance Spectroscopy of Nanostructure p-ZnGa_{2}Se_{4}/n-Si Heterojunction Diode

63%
Yahia I., Fadel M., Sakr G., Shenouda S., Yakuphanoglu F., Farooq W.
Acta Physica Polonica A
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2011
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vol. 120
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issue 3
563-566
EN
The impedance characteristics of the nanostructure p-ZnGa_2Se_4/n-Si heterojunction diode were investigated by impedance spectroscopy method in the temperature range (303-503 K) and the frequency range (42 Hz-5 MHz). The real and imaginary parts of the complex impedance are changed with the frequency. Both are decreased with increasing temperature at the lower frequencies and are merged at the higher frequencies. The dielectrical relaxation mechanism of the diode was analyzed by the Cole-Cole plots. The Cole-Cole plots under various temperatures exhibit one relaxation mechanism. With increasing temperature, the radius of the Cole-Cole plots decreases, which suggests a mechanism of temperature-dependent on relaxation.
3
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The Design Aspects for Ultra Low-Power, Low-Noise 90 nm CMOS Charge Sensitive Amplifier for the Active Pixel Detector

63%
Barzdenas V., Navickas R.
Acta Physica Polonica A
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2009
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vol. 115
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issue 6
1139-1140
EN
A falling particle in the digital registration systems for elementary particles active pixel detector induces electric charge, the value of which describes the parameters of the particle in the detector. Since the electric charge induced by a single particle is relatively weak, the detector signal is first processed (amplified and shaped) right in the zone of irradiation and only then transmitted further. This paper analyses the primary analogical registration electronics for digital registration systems for elementary particles active pixel detectors, which is charge sensitive amplifiers operating in the nanoampere region.
4
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Electron Charge Noise Minimization in 130 nm CMOS Preamplifiers

63%
Barzdenas V., Navickas R.
Acta Physica Polonica A
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2008
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vol. 113
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issue 3
825-828
EN
In this paper we present the design aspects for low-power, low-noise CMOS charge sensitive preamplifier that uses a leakage current compensation circuit for use with radiation sensors. The preamplifier has unipolar response with the peaking time of about 45 ns and the gain about 115-145 mV/ke. Equivalent noise charge (ENC) is less than 80 e, when the input charge is 1-20 ke and the sensors capacitance is equal to 30 fF. In this work we present the quality function of the charge sensitive preamplifier, which characterizes best the optimal input transistor width W, with respect to equivalent noise charge and to the power consumptions.
5
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Impedance Spectroscopy of Au-CdTe:Ga Schottky Contacts

51%
Płaczek-Popko E., Trzmiel J., Gumienny Z., Wojtyna E., Szatkowski J.
Acta Physica Polonica A
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2008
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vol. 114
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issue 5
1279-1283
EN
The dielectric response of Au-CdTe gallium doped Schottky contacts was investigated by impedance spectroscopy in the frequency range from 0.2 Hz to 3 MHz, at temperatures in the range from 77 K to 300 K. Combined modulus and impedance spectroscopic plots were analyzed to study the response of the structure. The data were fitted with the simple RC circuit composed of a depletion layer capacitance in parallel with resistance and a series resistance of the bulk CdTe:Ga. The activation energy of the bulk trap obtained from the Arrhenius plot of the resistance was found to be equal to 0.08 eV, close to the value 0.09 eV obtained from the impedance-modulus spectroscopy. The trap dominant in CdTe:Ga is possibly the DX center related, as it has been observed that this is the dominant trap in the material.
6
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Robust Algorithm for Heart Rate (HR) Detection and Heart Rate Variability (HRV) Estimation

51%
Piotrowski Z., Różanowski K.
Acta Physica Polonica A
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2010
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vol. 118
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issue 1
131-135
EN
We present algorithm for Heart Rate detection based on Short-Term Autocorrelation Center Clipping method. This algorithm is dedicated for biological signal detection, electrocardiogram, in noisy environment with lot of artifacts. Using this algorithm is also possible detect the R pointers in the PQRST complex of the ECG signal. In this paper the new implementation of the heart rate variability estimation is also presented. HRV module is based on parametric and non-parametric methods of the power spectral density computation.
7
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Structural and Electrical Properties of Sintered Barium-Zinc-Titanate Ceramics

51%
Obradović N., Filipović S., Pavlović V., Paunović V., Mitrić M., Ristić M.
Acta Physica Polonica A
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2011
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vol. 120
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issue 2
322-325
EN
The aim of this work was an investigation of structural and electrical properties of sintered barium-zinc-titanate ceramics. Mixtures of BaCO_{3}, ZnO and TiO_{2} were mechanically activated in a planetary ball mill up to 80 minutes and sintered isothermally in air for 120 minutes at 1300°C. The phase composition in the BaCO_{3}-ZnO-TiO_{2} system after milling and sintering was analyzed using the XRD method. The existence of pure barium-zinc-titanate has been registered. Microstructure analyses were performed using SEM. The results of electric resistivity, capacitance and loss tangent of the sintered samples were correlated with the XRD and SEM results.
8
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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

51%
Kołtunowicz T., Zhukowski P., Fedotova V., Saad A., Larkin A., Fedotov A.
Acta Physica Polonica A
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2011
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vol. 120
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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.
9
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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

51%
Kołtunowicz T., Zhukowski P., Fedotova V., Saad A., Fedotov A.
Acta Physica Polonica A
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2011
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vol. 120
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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.
10
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The Investigation on the E-J Characteristics and the Role of Nanoparticle Concentration in Weakly Polar Magnetic Fluids

51%
Kurimský J., Dolník B., Marton K., Kolcun M., Tomčo L., Rajňák M., Timko M., Kopčanský P.
Acta Physica Polonica A
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2014
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vol. 126
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issue 1
246-247
EN
The paper presents investigation on the magnetic fluids that are stable colloidal suspensions of single-domain magnetic particles in a liquid carrier of dielectrics nature. Studies were made on the electric field vs. current density, e.i. E-J characterization commonly observed in insulating liquids under uniform low electric or magnetic fields. High performance oil was used as the dielectric carrier. The experiments were carried out at different volume concentrations of magnetite nanoparticles up to 4%.
11
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Wave Phenomena in High-Voltage Windings of Transformers

51%
Banaszak S., Gawrylczyk K.
Acta Physica Polonica A
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2014
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vol. 125
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issue 6
1335-1339
EN
Determination of mechanical condition of transformer active part can be performed utilizing frequency response of the windings. Many computing models were developed to evaluate behavior of the winding in wide frequency range using different numerical methods. Most of them utilizes finite elements, assuming axial symmetry, if possible. In other cases we need to use a three-dimensional model, which results in a significant reduction in the accuracy of modeling the geometry of the system, as well as the penetration of electromagnetic field into conductors. From a practical point of view, using computer of average performance, the windings can be modeled with at most 10 turns. From this reason mixed models are proposed, where the electric parameters of the winding are concentrated in the substitute RLC elements. Such models are known as "lumped parameter models". Since the parameters of real winding are distributed, the question arises concerning the necessity of taking into account wave phenomena in them. The method allowing this is known as "transmission line method". Measurements of frequency response are used in industry. There are still many problems with interpretation of test results. Computer modeling may be a helpful tool allowing to understand relation between the geometry of a winding and its frequency response. To fulfill this, models should give similar response as a real measurement. The paper describes a modified transmission line method used for modeling of a transformer winding's frequency response. There is described the model, its parameters, and exemplary solution compared to test data.
12
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Influence of External Factors on Results of Bushing tanδ and Capacitance Measurements

51%
Buchacz J., Szymanski Z.
Acta Physica Polonica A
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2012
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vol. 122
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issue 5
900-904
EN
The paper presents influence of external factors on results of bushing dissipation factor tanδ and capacity measurements performed on not energized transformer as well as with operation voltage using on-line method. There are discussed methods and real cases of measurements, with emphasized differences in results interpretation. Conclusions and literature are summarized.
13
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Electrical Characterization of Defects in Schottky Au-CdTe:Ga Diodes

51%
Dyba P., Płaczek-Popko E., Zielony E., Gumienny Z., Szatkowski J.
Acta Physica Polonica A
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2009
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vol. 116
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issue 5
944-946
EN
Deep electron states in gallium doped CdTe have been studied by deep-level transient spectroscopy method. The Schottky Au-CdTe diodes were processed to perform the investigations. Rectifying properties of diodes have been examined by the room temperature current-voltage and capacitance-voltage measurements. Deep-level transient spectroscopy measurements performed in the range of temperatures 77-350 K yield the presence of three electron traps. The thermal activation energies and apparent capture cross-sections have been determined from related Arrhenius plots. The dominant trap of activation energy E_2 = 0.33 eV and capture cross-section σ_2 = 3 × 10^{-15} cm^2 has been assigned to the gallium related DX center present in the CdTe material.
14
Content available remote

Admittance and Permittivity in Doped Layered TlGaSe_2 Single Crystals

51%
Dawood S., Fedotov A., Mammadov T., Zukowski P., Koltunowicz T., Saad A., Drozdov N.
Acta Physica Polonica A
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2014
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vol. 125
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issue 6
1267-1271
EN
In doped TlGaSe_2 crystals the phase transitions at low temperatures (100-170 K) were observed using admittance and dielectric spectroscopy in a temperature range of 80-320 K. The admittance and permittivity measurements in the studied samples indicated that after Fe or Tb doping by impurities with concentrations N_{imp} < 0.5 at.% nonequilibrium electronic phase transition is observed. Doping with N_{imp} > 0.5 at.% resulted in full suppression of this phase transition presence.
15
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Percolation Phenomena in Cu_{x}(SiO_{y})_{100-x} Nanocomposite Films Produced by Ion Beam-Sputtering

45%
Koltunowicz T., Zukowski P., Czarnacka K., Svito I., Fedotov A.
Acta Physica Polonica A
|
2015
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vol. 128
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issue 5
908-911
EN
In this paper the results of examinations of nanocomposites Cu_{x}(SiO_{y})_{100-x} produced by ion beam sputtering using argon ions were presented. The examinations were performed by the use of ac devices for measuring frequency in the range 50 Hz-1 MHz and temperatures from 81 K to 273 K. The measurements were performed for the samples directly after production. Based on temperature dependences of conductivity σ , which were determined at the frequency 100 Hz, the Arrhenius graphs were prepared. From these graphs conductivity activation energies ΔE were calculated. Dependences of conductivity and activation energy of electrons on the metallic phase content x at the frequency 100 Hz were determined. Analysis of the obtained dependences shows that conductivity is a parabolic function of the metallic phase content x in nanocomposites. Changes of activation energies of nanocomposites, in which metallic phase contents are in the ranges x < 12 at.% and x > 68 at.%, demonstrate negative values - metallic type of conductivity. In the range 12 at.% < x < 68 at.% activation energies have positive values - the dielectric type of conductivity. It was established that for the metallic phase content of about 68 at.% the real percolation threshold occurs, and the conduction changes from dielectric to metallic type.
16
Content available remote

Single Domain Wall Contribution to the Impedance of Amorphous Ferromagnetic Wire

45%
Ziman J., Šuhajová V., Kladivová M.
Acta Physica Polonica A
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2014
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vol. 126
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issue 1
82-83
EN
An experiment, measuring the changes of impedance in a magnetic wire, caused by the presence of a single domain wall was proposed. The results obtained from a magnetic wire with small helical anisotropy show that for lower frequencies (up to about 1 MHz), the presence of wall causes an increase in impedance, very probably due to the wall displacement. As frequency increases, the influence of the wall presence on the magnetic state causes the impedance to decrease in adjacent domains. For frequencies close to 10 MHz this effect overcomes the effect of wall displacement.
17
Content available remote

La-doped and La/Mn-co-doped Barium Titanate Ceramics

45%
Vijatović Petrović M., Bobić J., Grigalaitis R., Stojanović B., Banys J.
Acta Physica Polonica A
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2013
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vol. 124
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issue 1
155-160
EN
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.
18
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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

45%
Zhukowski P., Kołtunowicz T., Węgierek P., Fedotova J., Fedotov A., Larkin A.
Acta Physica Polonica A
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2011
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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}.
19
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Internal Barrier Layer Capacitance Effects in Neodymium Copper Tantalate Ceramics

45%
Szwagierczak D.
Acta Physica Polonica A
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2012
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vol. 121
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issue 1
205-207
EN
A new perovskite material Nd_{2/3}CuTa_4O_{12} was applied as a naturally formed internal barrier layer capacitor. The powder prepared by solid state synthesis and ball milling was pressed into pellets and sintered at 1180-1220°C. Dielectric properties of ceramic samples were characterized by impedance spectroscopic studies carried out in the temperature range from - 55 to 700C at frequencies 10 Hz ÷ 2 MHz. Two types of the dielectric response were revealed - a high frequency response attributed to grains which occurred at low temperatures, and a low frequency one related to grain boundaries which dominated at higher temperatures. Resistances and capacitances of grains were found to be two orders lower than those of grain boundaries. Two plateaus were observed in the dielectric permittivity versus frequency plots - a low frequency step corresponding to a high value of 10^4 and a high frequency step at a level of 40. Scanning electron microscopy observations and energy dispersive spectroscopy analysis confirmed that Nd_{2/3}CuTa_4O_{12} ceramics were composed of semiconducting grains and insulating oxygen-enriched grain boundaries. The formation of such an electrically heterogeneous system during the one step fabrication process in air leads to spontaneous internal barrier layer capacitance effects responsible for a high and relatively stable dielectric permittivity of the developed material.
20
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Temperature and Frequency Dependence Electrical Properties of Zn_{1-x}Ca_{x}O Nanoceramic

45%
Das T., Das B., Parashar K., Parashar S.
Acta Physica Polonica A
|
2016
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vol. 130
|
issue 6
1358-1362
EN
This work reports the temperature and frequency dependence electrical properties of Ca doped ZnO (Zn_{1-x}Ca_{x}O, x=0.01) nanoceramic synthesized by solid state reaction method. The X-ray spectra show that the synthesized powder has hexagonal wurtzite structure with space group P6₃mc. The average crystallite size decreases with Ca doping. The increase in oxygen positional parameter (u) indicates lattice distortion in the crystal structure. Doping with Ca caused a slight shift in the (101) plane peak towards lower diffraction angle. The formation of pores in field emission scanning electron microscopy micrograph may be due to the defect created by Ca substitution. The electrical property was investigated by impedance spectroscopy in the temperature range 300-500°C. The synthesized sample shows temperature dependence relaxation phenomena and negative temperature coefficient of resistance effects. Electrical conductivity (σ_{ac}) increases with increase in temperature as well as with frequency due to the drift mobility of electrons and hole by hopping conduction. Dielectric constant was found to decrease with increase in frequency and temperature. This decreases drastically in the magnitude of approximately < 10 times than the corresponding undoped one.
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