Search results

1

Study of Gas Permeation Through Thin ta-C:H Films

100%

Lackner J., Waldhauser W., Kahn M.

Acta Physica Polonica A

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2015

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vol. 127

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issue 4

1236-1239

EN

Protective ultra-thin barrier films gather increasing economic interest for controlling permeation and diffusion from the biological surrounding in implanted sensor and electronic devices in future medicine. Thus, the aim of this work was the investigation of the film thickness influence on the gas permeation barrier of ultra-thin, cytocompatible tetrahedral amorphous carbon (ta-C:H) films on polyimide (PI) foils. Plasma-activated chemical vapor deposition (direct deposition from an ion source) was applied to deposit these diamond-like carbon films. The results indicate high barrier to hydrogen gas permeation by all film thicknesses (<0.2% H₂ permeation compared to uncoated PI). While the thickness of the ta-C:H layers has minor influence, the number of layers, realized by one- or double-side deposition strongly impacts the barrier effect. Finally, tests under tensile stresses showed minor impact in the elasto-plastic deformation regime, but the expected strong increase of gas permeation after exceeding the tensile strength and film fracture.

2

Application of DC Magnetron Sputtering for Creation of Gas-Sensitive Indium Oxide Thin Films and Their Properties

63%

Luhin V., Zharsky I., Zhukowski P.

Acta Physica Polonica A

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2013

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vol. 123

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issue 5

837-839

EN

In this paper the technology of gas sensitive semiconductor structures based on indium oxide thin films by DC magnetron sputtering of indium with the subsequent thermal oxidation is developed. Structure, surface morphology and chemical composition of the obtained films have been investigated by electron diffraction, scanning electron microscopy, Auger electron spectroscopy, and X-ray photoelectron spectroscopy. Conditions of In_2O_3 films formation with high selectivity and sensitivity to NO_2, and NH_3 are established.

3

Effect of Post Annealing on La_{0.7}Sr_{0.3}MnO_3 Thin Films

63%

Cheng W., Leung C.

Acta Physica Polonica A

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2007

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vol. 111

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issue 1

117-122

EN

The stability of La_{0.7}Sr_{0.3}MnO_3 thin films fabricated by pulsed laser deposition, under different annealing procedures, was investigated. La_{0.7}Sr_{0.3}MnO_3 films were deposited on (100) LaAlO_3 substrates at 650ºC with the films thickness from 20 to 50 nm. The oxygen pressures used to fabricate the films were 150 mTorr and 100 mTorr. Then in situ annealing steps were performed at 100 and 150 mTorr, respectively. Curie temperatures (T_c) of the films were estimated from the peaks of the temperature dependent resistance data. For the films deposited at 100 mTorr and annealed at 150 mTorr, T_c slightly dropped for short annealing time and recovered to 360 K for 30 min annealing. For the films deposited at 100 mTorr and annealed at 150 mTorr, it maintained semiconducting behavior without transition after annealing up to 30 minutes. For ex situ post annealing, it was found that the T_c of the films strongly depended on the annealing procedures.

4

Interface Mixing in Fe/Si Multilayers Observed by the In Situ Conductance Measurements

63%

Chomiuk P., Błaszyk M., Szymański B., Luciński T.

Acta Physica Polonica A

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2009

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vol. 115

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issue 1

355-356

EN

In this contribution the in situ conductance vs. deposition time dependences of Fe/Si multilayers are analysed. The plot of resistance multiplied by the square of the thickness as a function of iron thickness shows that during the iron deposition initially amorphous-like Fe-Si mixture is formed, next the mixture crystallises, and finally bcc-Fe phase appears. The interface mixing is also manifested by the reduction of the total multilayer thickness measured by small angle X-ray diffraction.

5

Quantum Transport in Thin-Film Structures

63%

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.

6

Impurity-Scattering Limited Electron Mobility in Free Standing Quantum Wires: Image Charge Effect

63%

Vagner P., Mos̆ko M.

|

EN

We calculate the impurity-scattering limited mobility of the one-dimensional electron gas in a rectangular GaAs quantum wire confined in the vertical (growth) direction by n-modulation doped AlGaAs layers and free standing along the transverse direction. The scattering potential of the ionized impurity is obtained by solving the Poisson equation with z-dependent electrostatic permittivity in order to take into account the image charge effect due to the abrupt permittivity change at the GaAs/air interfaces. We show that the "image impurity" scattering tends to drastically reduce the electron mobility for sufficiently small (≈10 nm) transverse wire widths.

7

AFM, XRD and HRTEM Studies οf Annealed FePd Thin Films

51%

Perzanowski M., Zabila Y., Morgiel J., Polit A., Krupiński M., Dobrowolska A., Marszałek M.

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issue 2

423-426

EN

Ferromagnetic FePd L 1_{0} ordered alloys are highly expected as forthcoming high-density recording materials, because they reveal a large perpendicular magnetocrystalline anisotropy [1]. The value of the magnetic anisotropy of FePd alloy strongly depends on the alloy composition, degree of alloy order as well as on the crystallographic grain orientation. In particular, to obtain the perpendicular anisotropy, it is necessary to get the films with (001) texture. One of the successful methods, which allows one to obtain highly ordered alloy, is a subsequent deposition of Fe and Pd layers, followed by an annealing at high temperature. This paper presents the study of the FePd thin alloy film structure changing in the result of high temperature annealing. During the annealing in high vacuum, the measurements of electrical resistance were performed, indicating the regions of different structure evolution. Changes in the crystal structure and surface morphology induced by thermal treatment were investigated by X-ray diffraction, atomic force microscopy, as well as high resolution transmission electron microscopy and then compared with electrical resistivity measurement. The slow thermal annealing of the deposited layers leads to the formation of L 1_{0} ordered FePd alloy with preferred (111) grain orientation. After the annealing at the highest used temperature, the dewetting process was observed, resulting in a creation of well oriented, regular nanoparticles.

8

Effect of Molecular Orientation on Photovoltaic Efficiency and Carrier Transport in a New Semiconducting Polymer

51%

Kažukauskas V., Pranaitis M., Sentein C., Rocha L., Raimond P., Duyssens I., Van Severen I., Lutsen L., Cleij T., Vanderzande D.

Acta Physica Polonica A

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2008

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vol. 113

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issue 3

1009-1012

EN

New functionalized soluble poly(p-phenylene vinylene) derivative bearing polar molecules was designed and synthesized in order to investigate effects of molecular orientation in polymer photovoltaic devices. The active polar molecule is the 4-(N-butyl-N-2-hydroxyethyl)-1- nitro-benzene group. The grafting of the push-pull molecule with a donor/transmitter/acceptor structure, possessing a large ground state dipole moment, enables the molecular orientation by a dc electric field. An internal electric field stored in such system facilitates exciton dissociation and improves charge transport in single-layer devices. In our systems an increase in the external quantum efficiency by a factor of about 1.5 to 2 is estimated. The associated effects of orientation on the carrier injection and transport properties were evidenced.

9

Magnetization Reversal in Cobalt Nanocolumn Structures Obtained by Glancing Angle Deposition

51%

Buchta K., Schmidt C., Trykowski G., Biniak S., Kempiński M., Luciński T.

Acta Physica Polonica A

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2012

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vol. 121

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issue 5-6

1222-1224

EN

An advanced deposition technique known as glancing angle deposition was used to fabricate randomly seeded magnetic cobalt columnar nanostructures. The existence of nanocolumns was confirmed by the cross-section scanning electron microscopy. The evolution in the magnetization reversal mechanism as a function of the film thickness was investigated. The coercivity H_{C} and M_{R}/M_{S} ratio (where M_{R} and M_{S} denote the remanent and saturation magnetization, respectively), derived from the magnetic hysteresis loops, are discussed as a function of the angle between the external magnetic field and the surface normal. The direction of the magnetization easy/hard axis and the columns inclination angle were determined on the basis of the angular dependences of the H_{C} and the M_{R}/M_{S}. A crossover from the coherent rotation, based on the Stoner-Wohlfarth model, to the curling reversal mode was observed.

10

On the Validity of Diffusional Model in Determination of Electric Transport Parameters of Semiconductor Compound

51%

Dussan A., Mesa F.

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vol. 125

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issue 2

171-173

EN

In this work we have studied the variable range hopping as a predominant electronic transport mechanism for semiconductor materials used as absorbent layer in photovoltaic devices. Dark conductivity measurements were carried out from 120 to 420 K in Si, Cu_3BiS_3, SnS, Cu_2ZnSnSe_4, and CuInGaSe_2 thin films. In the low-temperature range, variational range hopping was established for all samples. Using classical equations from the percolation theory and the diffusional model, the density of states near the Fermi level (N_{F}), as well as the hopping parameters (W - activation energy and R - hopping range) were calculated. A correlation between both models allowed us to evaluate the validity of the diffusional model in semiconductor compounds.

11

Near-Band Edge Spectral Hole in Quantum Well: No Evidence for Subpicosecond Plasma Thermalization

51%

Mos̆ko M., Mos̆ková A.

Acta Physica Polonica A

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1996

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vol. 90

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issue 5

1055-1059

EN

We show that at low carrier energies and densities the carriers in a two-dimensional Coulomb gas interact via classical unscreened carrier-carrier collisions. This allows us to calculate exactly the thermalization due to the two-dimensional carrier-carrier collisions in a nonthermal low-density (≈10^{10} cm^{-2}) two-dimensional plasma excited near the band edge of an undoped GaAs quantum well. The thermalization is found to be 10-15 times slower than the 200 fs thermalization deduced from the previous spectral-hole burning measurements, which means that the spectral hole does not reflect the thermalization process. We also show that the Born approximation fails in describing such carrier-carrier collisions.

12

Magnetoresistive Properties of Manganite-Based Heterojunctions

51%

Devenson J., Vengalis B., Lisauskas V., Oginskis A., Anisimovas F., Ašmontas S.

Acta Physica Polonica A

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2009

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vol. 115

|

issue 6

1130-1132

EN

Hole-doped La_{2/3}Ba_{1/3}MnO_{3} (LBaMO), La_{2/3}Ca_{1/3}MnO_{3} (LCaMO) and La_{2/3}Ce_{1/3}MnO_{3} (LCeMO) thin films were grown heteroepitaxially on 0.1 wt.% Nb-doped SrTiO_{3}(100) (STON) substrates by magnetron sputtering. The prepared LBaMO/STON, LCaMO/STON, LCeMO/STON heterostructures demonstrated nonlinear rectifying current-voltage characteristics. Negative magnetorestance values have been indicated at low bias, meanwhile bias-dependent magnetoresistance has been measured at positive bias voltage values U > U_d where U_d is the interfacial potential, corresponding to a steep current increase at a forward bias.

13

Electrical Characterization of Ammonia Carbon-Based Sensors

51%

Kościński M., Seredych M., Bandosz T., Śliwińska-Bartkowiak M.

Acta Physica Polonica A

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2015

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vol. 128

|

issue 2

182-184

EN

A sensor response parameters of the ammonia sensors which are prepared by using composite of graphene oxide and poly(4-styrenesulfonic acid-co-maleic acid) sodium salt derived carbon are presented. Using the self-designed interdigitated electrode on the experimental setup, we were able to determine the capacity for gas sensing as a sensor response for low ammonia concentrations (20, 50, and 100 ppm).

14

Synthesis and Electrical Properties of La-Pr-Mn-O Thin Films and Heterostructures

51%

Butkutė R., Anisimovas F., Oginskis A., Steikūnienė A., Devenson J., Vengalis B.

Acta Physica Polonica A

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2007

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vol. 111

|

issue 1

111-115

EN

In this paper we report the results of synthesis and study of both ceramic samples and thin films of electronically doped La_{0.7}Pr_{0.3}MnO_3 and related heterostructures composed of La_{0.7}Pr_{0.3}MnO_3 and p-type La_{0.67}Ca_{0.33}MnO_3. The ceramic La_{0.7}Pr_{0.3}MnO_3 samples were prepared by a conventional solid state reaction technique. Single phase La_{0.7}Pr_{0.3}MnO_3 thin films and La_{0.7}Pr_{0.3}MnO_3/La_{0.67} Ca_{0.33}MnO_3 heterostructures were grown on lattice-matched perovskite NdGaO_3 substrates by pulsed laser deposition. Electron doping was indicated both for ceramic La_{0.7}Pr_{0.3}MnO_3 samples and thin films from thermopower data. Both ceramic samples and thin films of La_{0.7}Pr_{0.3}MnO_3 demonstrated resistivity of about 10 mΩ cm at 300 K and semiconductor-like resistance vs. temperature behavior with cooling down to 78 K. Meanwhile, the resistance of the La_{0.7}Pr_{0.3}MnO_3/La_{0.67}Ca_{0.33}MnO_3 interface showed an anomalous peak at 185 K. A series of post-deposition annealing experiments demonstrated a crucial role of annealing temperature and ambience on both electrical and magnetic properties of La_{0.7}Pr_{0.3}MnO_3 material and the heterostructures.

15

Transport and Relaxation of Charge in Organic-Inorganic Nanocomposites

51%

Olenych I., Aksimentyeva O., Tsizh B., Horbenko Y.

Acta Physica Polonica A

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2018

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vol. 133

|

issue 4

851-855

EN

In this work the nanocomposites of poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate) host matrix with porous silicon and ZnO nanoparticles were manufactured. The charge transport and relaxation processes in organic-inorganic nanocomposites were analyzed based on complex studies of electrical conductivity and depolarization current in the wide temperature range. By means of impedance spectroscopy we have established that increase of content of ZnO nanoparticles causes the rise in the internal resistance of the hybrid films. Based on the spectra of thermally stimulated depolarization current the localized electron states in the experimental samples are found. The combination of the porous silicon and zinc oxide nanoparticles provides an increase of surface area of the sensors and their high sensitivity to water molecules.

16

Magneto- and Electroresistance of Ultrathin Anisotropically Strained La-Sr-MnO Films

51%

Balevičius S., Stankevič V., Žurauskienė N., Šimkevičius Č., Paršeliūnas J., Cimmperman P., Abrutis A., Plaušinaitienė V.

Acta Physica Polonica A

|

2005

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vol. 107

|

issue 1

203-206

EN

The magnetoresistance anisotropy of ultrathin La_{0.83}Sr_{0.17}Mn O_3 films deposited on NdGaO_3 substrate by metalorganic chemical vapour deposition technique was investigated. The electric-field-induced resistance change was studied up to electric fields of 10 kV/cm using ns duration electrical pulses. It was found that in ultrathin (< 10 nm) and thin (< 50 nm) films the origin of electric-field-induced resistance change is thermal. However, the films with thicknesses of about 20 nm, exhibit negative electric-field-induced resistance change, having a pure electronic nature. This effect is explained in terms of two-layer systems with imperfections located at the interface between the layers.

17

Broad Band THz Sensing by 2DEG Bow-Tie-Type Diodes

51%

Valušis G., Seliuta D., Tamošiūnas V., Širmulis E., Balakauskas S., Gradauskas J., Sužiedėlis A., Ašmontas S., Anbinderis T., Narkūnas A., Papsujeva I., Lisauskas A., Roskos H., Köhler K.

Acta Physica Polonica A

|

2005

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vol. 107

|

issue 1

184-187

EN

We suggest a novel approach to detect broad band, 0.078-2.52 THz, electromagnetic radiation at room temperature using an asymmetrically-shaped bow-tie diode based on a modulation-doped GaAs/AlGaAs structure. We show that the voltage sensitivity in the range from 0.078 THz up to 0.8 THz has a plateau and its value is within 0.3-0.5 V/W. We consider the bow-tie diode design to increase the sensitivity of the device.

18

Photoconductivity Study of Sputter-Deposited Cu_2O Films

51%

Bhattacharyya S., Reppin D., Sanguino P., Ayouchi R., Polity A., Schwarz R., Hofmann D., Meyer B.

Acta Physica Polonica A

|

2011

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vol. 120

|

issue 6A

A-11-A-14

EN

Cuprous oxide (Cu_2O) thin films were deposited by radio frequency sputtering technique on fused silica substrates. The X-ray diffraction study of the Cu_2O samples showed reflections from (111) and (200) planes of cubic Cu_2O. The samples were then annealed at 1008 K in nitrogen (N_2) atmosphere. Annealed samples indicated strain relaxation. The samples were then characterized optically by measuring the transmittance using an ultraviolet-visible-near infrared photospectrometer. The band gap of the as-deposited samples were found to be ≈ 2.1 eV, whereas the annealed samples had a band gap of ≈ 2.6 eV. The transient photocurrent decay measurements of the annealed films indicated slow non-exponential power law decays in several time windows, indicating multiple trapping of the carriers in the deep defects within the band gap. The steady-state photo and dark current measurement and persistent photocurrent (PPC) was carried out on the annealed samples. In general, the photocurrent was found to be much smaller than the dark current. The steady-state and transient photocurrent measurements were utilized to determine the carrier lifetime-mobility product, 〈μτ 〉 of the samples and to determine the carrier mobility, 〈μ 〉.

19

Electrical Resistivity of the Monoatomic Metallic Layer

51%

Paja A., Działo A.

Acta Physica Polonica A

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2013

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vol. 123

|

issue 4

770-772

EN

We present new formula which describes the change of electrical resistivity of a monoatomic metallic layer with temperature. The results are compared with those given by the Bloch-Grüneisen formula for bulk metals. Our calculated values compared with those for bulk materials are significantly higher at low temperatures (T<0.1θ) and apparently lower at the remaining range of temperatures. Both effects can be explained by the low dimensionality of the sample.

20

Annealing Effect on Dark Electrical Conductivity and Photoconductivity of Ga-In-Se Thin Films

51%

Isik M., Gullu H.

Acta Physica Polonica A

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2018

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vol. 133

|

issue 5

1119-1124

EN

Dark-conductivity and photoconductivity properties of thermally evaporated Ga-In-Se (GIS) thin films were investigated in the temperature range of 80-430 K. All measurements were performed on as-grown and annealed GIS thin films at 300 and 400° to get information about the effect of the annealing temperature on the conductivity properties. Room temperature conductivity was obtained as 1.8 × 10^{-8} Ω^{-1} cm^{-1} for as-grown films and increased to 3.6 × 10^{-4} Ω^{-1} cm^{-1} for annealed films at 400°. Analysis of the dark-conductivity data of as-grown films revealed nearly intrinsic type of conductivity with 1.70 eV band gap energy. Temperature dependent dark conductivity curves exhibited two regions in the 260-360 and 370-430 K for both of annealed GIS films. Conductivity activation energies were found as 0.05, 0.16 and 0.05, 0.56 eV for films annealed at temperatures of 300 and 400°, respectively. The dependence of photoconductivity on illumination intensity was also studied in the range from 17 to 113 mW/cm^{2}.

Refine search results

Study of Gas Permeation Through Thin ta-C:H Films

Application of DC Magnetron Sputtering for Creation of Gas-Sensitive Indium Oxide Thin Films and Their Properties

Effect of Post Annealing on La_{0.7}Sr_{0.3}MnO_3 Thin Films

Interface Mixing in Fe/Si Multilayers Observed by the In Situ Conductance Measurements

Quantum Transport in Thin-Film Structures

Impurity-Scattering Limited Electron Mobility in Free Standing Quantum Wires: Image Charge Effect

AFM, XRD and HRTEM Studies οf Annealed FePd Thin Films

Effect of Molecular Orientation on Photovoltaic Efficiency and Carrier Transport in a New Semiconducting Polymer

Magnetization Reversal in Cobalt Nanocolumn Structures Obtained by Glancing Angle Deposition

On the Validity of Diffusional Model in Determination of Electric Transport Parameters of Semiconductor Compound

Near-Band Edge Spectral Hole in Quantum Well: No Evidence for Subpicosecond Plasma Thermalization

Magnetoresistive Properties of Manganite-Based Heterojunctions

Electrical Characterization of Ammonia Carbon-Based Sensors

Synthesis and Electrical Properties of La-Pr-Mn-O Thin Films and Heterostructures

Transport and Relaxation of Charge in Organic-Inorganic Nanocomposites

Magneto- and Electroresistance of Ultrathin Anisotropically Strained La-Sr-MnO Films

Broad Band THz Sensing by 2DEG Bow-Tie-Type Diodes

Photoconductivity Study of Sputter-Deposited Cu_2O Films

Electrical Resistivity of the Monoatomic Metallic Layer

Annealing Effect on Dark Electrical Conductivity and Photoconductivity of Ga-In-Se Thin Films