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1
Content available remote

Quantum Transport in Thin-Film Structures

100%
Bułka B., Barnaś J.
Acta Physica Polonica A
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1994
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vol. 85
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issue 2
465-468
EN
General quantum-mechanical description of electronic transport in thin-film structures, which is based on the Kubo approach, is presented and applied to a single film with ideal surfaces. The cases of a constant chemical potential and a constant particle number are considered and analysed numerically.
2
Content available remote

Electrical Resistance Anomalies in Holmium Thin Films below 20 K in Magnetic Field

80%
Dudáš J., Gabáni S., Kavečanský V., Gościańska I., Bagi J.
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issue 5
843-845
EN
Electrical resistance (R) of Ho thin films evaporated in vacuum ≈ 10^{-7} Pa was studied in a temperature range from 2 K up to 300 K and in magnetic field up to 9 T. Measurements showed resistance anomalies below 20 K - minima of R value in 36 nm and 215 nm thin films and resistivity maximum at 3.58 K in 215 nm Ho film. Increasing value of the magnetic field, applied perpendicular to film surface up to 5 T, caused increasing suppression of the R minima in these films with subsequent disappearance of them in fields above 5 T. Maximum of R value in 215 nm thin film at 3.58 K decreased with increasing flux density up to 5 T and it was suppressed at fields above 5 T. X-ray diffraction of these films revealed two phases composition consisting of the hexagonal Ho and of cubic HoH_2. The preferential crystal orientation of both phases was detected.
3
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Electrical Properties of Aluminum Oxide-Ethylene Glycol (Al₂O₃-EG) Nanofluids

80%
Fal J., Żyła G., Gizowska M., Witek A., Cholewa M.
Acta Physica Polonica A
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2015
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vol. 128
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issue 2
153-155
EN
Nanofluids are suspensions of nanometrical size particles in a liquid base, which is usually water, oil or ethylene glycol. The potential practical use of nanofluids caused in recent years a considerable intensification of research into their properties. The most widely studied of physical properties include the fluid rheology, thermal conductivity and electrical parameters. The paper presents electrical properties of aluminium oxide (Al₂O₃) nanofluids based on ethylene glycol (EG). Nanoparticles used to produce nanosuspensions employed in measurements have size between 100-300 nm. Electrical properties was investigated in a wide range of temperatures (-10°C-55°C) and frequencies (0.02-200 kHz) using a measuring LCR bridge connected to a temperature stabilization system based on liquid nitrogen and Peltier element.
4
Content available remote

Effects of Substrate Temperature on Structural Properties of Tin Oxide Films Produced by Plasma Oxidation after Thermal Evaporation

80%
Alaf M., Guler M., Gultekin D., Akbulut H.
Acta Physica Polonica A
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2013
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vol. 123
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issue 2
326-329
EN
In this study, tin film was thermally evaporated onto a stainless steel substrate in an argon atmosphere. The tin films were then subjected to a DC plasma oxidation process using an oxygen/argon gas mixture. Three different substrate temperatures (100°C, 150°C, and 200°C) and three different oxygen partial pressures (12.5%, 25%, and 50%) were used to investigate the physical and microstructural properties of the films. The surface properties were studied by scanning electron microscopy, X-ray diffraction, atomic force microscopy and a four-point probe electrical resistivity measurement. The grain size and texture coefficient of the tin oxide films were calculated. Both SnO and SnO_2 films with grain sizes of 13-43 nm were produced, depending on the oxygen partial pressure. SnO films have flower- and flake-like nanostructures, and SnO_2 films have grape-like structures with nanograins. The resistivity values for the SnO_2 phase were found to be as low as 10^{-5} Ω cm and were observed to decrease with increasing substrate temperature.
5
Content available remote

Influence of Thickness and Magnetic Field on Magnetic Ordering Temperatures in Holmium Thin Films

80%
Dudáv J., Guzan M., Gabáni S., Kavečanský V., Gošciańska I., Vincze A., Konč M.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
191-195
EN
Influence of thickness and magnetic field on magnetic ordering temperatures is reported. The X-ray diffraction of Ho films confirmed their preferential crystal orientation and revealed diffraction peaks originating from the hcp structure of Ho and those from inessential holmium dihydride content. Secondary ion mass spectroscopy showed a very homogeneous distribution of holmium in thin films. Electrical resistance measurements on Ho films in the thickness range from 98 nm to 215 nm showed a "knee-like" resistance anomaly near the T_N. The T_N value of these films decreased with decreasing film thickness. Magnetic field applied parallel to the thin film plane caused an increasing suppression of the T_N value up to 5 K with increasing flux density value up to 5 T.
6
Content available remote

Resistance Properties of Al-Si Coatings

80%
Kucharska B., Kowalczyk J.
Acta Physica Polonica A
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2016
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vol. 129
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issue 2
197-199
EN
Modern methods for modification of properties and protection of material surface, which embrace gaseous phase physical deposition methods, arouse interest of many branches of industry as well as medicine. By virtue of their fine-grained structure, metallic coatings fabricated by these methods have superior mechanical properties and corrosion resistance when compared with alloys made by traditional techniques. The paper presents a study of the electrical properties and structure of Al-Si coatings. The coatings were deposited by physical vapor deposition. Targets of hypo-, peri- and hypereutectic composition alloys were sputtered using the magnetron process. The coatings were the resistance element in the dc current circuit and measurements were carried out by the four-point method. Based on current-voltage parameters, the coatings electrical resistance was determined at specified temperatures. It was found that an increase of Si content in the chemical composition of the coatings resulted in an increase of their resistance and the maximum temperature to which the coating heats up. By means of a X-ray diffraction the occurrence of thin film of aluminum and silicon oxides on the coatings surface were detected. The oxide film increases resistance of the coatings and hamper measurements at low voltage.
7
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Preparation and Characterization of Copper Powders with Sn Coating by the Electroless Plating

80%
Uysal M., Cetinkaya T., Gul H., Kartal M., Algul H., Tokur M., Alp A., Akbulut H.
Acta Physica Polonica A
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2015
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vol. 127
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issue 4
1106-1108
EN
In this work, Sn-Cu composite powders were produced using an electroless process. The tin content on the surface of copper powders was varied by using different concentrations of SnSO₄ in the plating bath. The surface morphology of the produced Sn-Cu composite powders was characterized using scanning electron microscopy (SEM). Energy dispersive spectroscopy (EDS) was used to determine the elemental surface composition of the composites. X-ray diffraction (XRD) analysis was performed to investigate the structure of the Sn-Cu composite powders. The electrochemical performance of Sn-Cu nanocomposites was studied by charge/discharge tests.
8
Content available remote

Tin/Tinoxide (Sn/SnO_2) Nanocomposites Thin Films as Negative-Electrode Materials for Li-Ion Batteries

70%
Alaf M., Gultekin D., Akbulut H.
Acta Physica Polonica A
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2013
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vol. 123
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issue 2
323-325
EN
In this study, tin/tinoxide (Sn/SnO_2) nanocomposites thin films were produced by thermal evaporation and plasma oxidation as anode materials for Li-ion batteries. To produce Sn/SnO_2 thin films, pure metallic tin (Sn) was thermally evaporated on the stainless steel substrates in argon atmosphere. The Sn films were subjected to plasma oxidation process at oxygen/argon gas mixture. Three different plasma oxidation times (30, 45, and 60 min) were used to investigate oxidation kinetics and physical and microstructural properties. The surface properties were studied by scanning electron microscopy and atomic force microscopy. For structural analysis, X-ray diffraction measurements were carried out. Sn/SnO_2 coated stainless steel substrates were used as the working electrode in coin-type (CR2016) test cells. The energy storage capacity Sn/SnO_2 electrodes were determined depending on the oxidation time and Sn:SnO_2 ratio.
9
Content available remote

Characterization of Bimetallic Systems with UPS and PAX: Gold on Platinum and Palladium Surfaces

70%
Moors M., Kobiela T., Krupski A., Becker C., Wandelt K.
Acta Physica Polonica A
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2008
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vol. 114
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issue S
S-77-S-92
EN
In the present study the thermal behavior of ultrathin Au films deposited on different noble metal single crystal surfaces was studied by means of ultraviolet photoelectron spectroscopy and photoemission of adsorbed xenon. The primary goal of this work was to demonstrate the power of photoemission of adsorbed xenon as an easy to handle and very surface sensitive technique for the characterization of multi-component systems. All investigated systems, Au-Pt(111), Au-Pd(111) and Au-Pd(110) show a particular dependence of their electronic and structural properties on the annealing temperature. Au multilayer films with a thickness of 3 monolayer prepared at 150 K undergo in all cases a smoothening by annealing up to room temperature. While on Pd this effect is mainly detectable on the topmost atomic layer the ordering process on Pt is also affecting the deeper layers. Further annealing of the Au-Pd system to 450 K and the Au-Pt system to 750 K, respectively, results in the onset of the alloying process at the interface between metal film and substrate. After annealing to 650 and 950 K, respectively, the alloying finally extends to the very surface. The complete loss of Au from the surface can be detected at 1050 K on Pd and at 1150 K on Pt. The orientation of the substrate has only a weak influence, showing up e.g. in additional electronic states of the not alloyed Au-Pd(111) and Au-Pd(111) systems. Adsorption of CO as a probe molecule illustrates the formation of different adsorption sites on the bimetallic systems during the Au diffusion process.
10
Content available remote

First-Principles Calculations of Structural, Electronic, Optical, and Thermodynamic Properties of CdS, CdTe and Their Ternary Alloys CdS_{1-x}Te_{x} (0.0 ≤ x ≤1.0)

70%
Ameri M., Mesbah S., Al-Douri Y., Bouhafs B., Varshney D., Ameri I.
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vol. 125
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issue 5
1110-1117
EN
Using first-principle method, we investigate the structural, electronic, optical, and thermodynamic properties of the CdS_{1-x}Te_x semiconductor alloys using generalized gradient approximation for the exchange-correlation potential calculation. The ground state properties are determined for the bulk materials (CdS and CdTe) in cubic phase. Quantities such as the lattice constants and bulk modulus of interest are calculated. Detailed comparisons are made with published experimental and theoretical data and show generally good agreement. The calculated lattice constants scale linearly with composition (Vegard's law). The microscopic origins of the bowing parameter were explained using the contributions from volume deformation, charge transfer and structural relaxation approach. The refractive index and optical dielectric constant for the alloys of interest were calculated by using different models. In addition, the thermodynamic stability of the alloys was investigated by calculating the critical temperatures of alloys.
11
Content available remote

Model of Anisotropic Electrical Resistivity in Rough Thin Films

70%
Szumiata T., Gzik-Szumiata M.
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issue 5
859-860
EN
In this work a new model of electrical resistivity is proposed in order to study the relationship between surface roughness geometry and thin films resistivity. The model is based on the numerical dynamic averaging of electron mean free path over whole simulated structure of rough film. For current-in-plane configuration the resistivity increases with decreasing film thickness faster than for current-perpendicular-to-plane one. Our simulations showed that big roughness depth and fine in-plane spatial period of roughness are crucial factors increasing the resistivity of ultrathin metallic layers.
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