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1
Content available remote

Epitaxial ZnO Films Grown at Low Temperature for Novel Electronic Application

100%
Wachnicki Ł., Dużyńska A., Domagala J., Witkowski B., Krajewski T., Przeździecka E., Guziewicz M., Wierzbicka A., Kopalko K., Figge S., Hommel D., Godlewski M., Guziewicz E.
Acta Physica Polonica A
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2011
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vol. 120
|
issue 6A
A-7-A-10
EN
Monocrystalline films of zinc oxide were grown at 300C by atomic layer deposition. ZnO layers were grown on various substrates like ZnO bulk crystal, GaN, SiC and Al_2O_3. Electrical properties of the films depend on structural quality. Structural quality, surface morphology and optical properties of ZnO films were characterized using X-ray diffraction, scanning electron microscopy, and photoluminescence, respectively. High resolution X-ray diffraction spectra show that the rocking curve FWHM of the symmetrical 00.2 reflection equals to 0.058° and 0.009° for ZnO deposited on a gallium nitride template and a zinc oxide substrate, respectively. In low temperature photoluminescence sharp excitonic lines in the band-edge region with a FWHM equal to 4 meV, 5 meV and 6 meV, for zinc oxide deposited on gallium nitride, zinc oxide and sapphire substrate, respectively.
2
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Effect of Annealed (0001) α-Al_2O_3 Surfaces on Heteroepitaxial Growth of Silver Nanoparticles

100%
Al-Mohammad A.
Acta Physica Polonica A
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2009
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vol. 115
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issue 3
679-684
EN
The effect of annealed (0001) α -Al_2O_3 surfaces on heteroepitaxial growth of silver nanoparticles were analysed by reflection high-energy electron diffraction, transmission electron microscope and selected area electron diffraction. Ag nanoparticles were deposited on 1× 1 stoichiometric and reconstructed (111)Al//(0001) α -Al_2O_3 with the Knudsen cell. The maximum cluster density method and the Lifethenz theory of Van der Waals energy were used to investigate the Ag//(0001)α -Al_2O_3 interface parameters. The growth modes, lattice parameters, nanoparticle forms and sizes are strongly dependent on the substrate surface structures. Initially, three-dimensional islands of Ag nanoparticles grow on both kinds of surfaces with partial hexagonal shapes. Ag nanoparticles on stoichiometric surface create the (111)Ag//(0001)α -Al_2O_3 interface without any preferred epitaxial direction. On this surface, Gaussian distribution is characteristic of an atom-by-atom growth mode with density of Ag nanoparticles lower than saturation density while a coalescence growth mode appears due to binary collisions between Ag nanoparticles accompanied by a liquid-like behaviour after saturation density. In case of reconstruction substrates, the epitaxial relationships between Ag nanoparticles and the surface are formed (111)Ag//(0001)α -Al_2O_3, 〈01\bar(1)〉Ag//[12\bar(3)0]α -Al_2O_3 or 〈01\bar(1)〉Ag//[1\bar(1)00]α-Al_2O_3. The Ag nanoparticles make rotation with angles between ± 6° around the epitaxial orientations 〈1\bar(1)00〉 or 〈12\bar(3)0〉. Only the atom-by-atom growth mode were found at all Ag nanoparticles growth processes.
3
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Optical and Structural Characterization of Zinc Oxide Nanostructures Obtained by Atomic Layer Deposition Method

100%
Wachnicki Ł., Witkowski B., Gierałtowska S., Kopalko K., Godlewski M., Guziewicz E.
Acta Physica Polonica A
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2011
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vol. 120
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issue 5
905-907
EN
Zinc oxide is a II-VI semiconductor material which is gaining increasing interest in various fields such as biology, medicine or electronics. This semiconductor reveals very special physical and chemical properties, which imply many applications including a transparent electrode in solar cells or LED diodes. Among many applications, ZnO is also a prospective material for sensor technology, where developed surface morphology is very advantageous. In this work we present ZnO nanowires growth using atomic layer deposition method. ZnO nanowires were obtained using controlled physical properties. As a substrate we used gallium arsenide with gold-gallium eutectic droplets prepared on the surface at high temperature. To obtain the eutectic solution there was put a gold thin film on GaAs through the sputtering and then we annealed the sample in a nitrogen gas flow. The so-prepared substrate was applied for growth of ZnO nanowires. We used deionized water and zinc chloride as oxygen and zinc precursors, respectively. The eutectic mixture serves as a catalyst for the ZnO nanowires growth. Au-Ga droplets flow on the front of ZnO nanowires. Scanning electron microscopy images show ZnO nanorods in a form of crystallites of up to 1 μm length and a 100 nm diameter. It is the first demonstration of the ZnO nanowires growth by atomic layer deposition using the vapour-liquid-solid approach.
4
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Synthesis, Structural and Optical Properties of Mo-Doped ZnO Thin Films

100%
Mekki A., Tabet N.
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vol. 125
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issue 2
365-367
EN
Transparent zinc oxide thin films doped with molybdenum have been prepared using a DC reactive magnetron sputtering on glass substrates from metallic ZnMo target. The three films, called A, B, and C, had 1.9 at.% Mo, 2.8 at.% Mo and 4.7 at.% Mo, respectively. The composition of the films was determined by X-ray photoelectron spectroscopy. The analysis of Mo 3 d_{5/2} core level spectra indicated that Mo exist in the films in Mo^{6+} oxidation state irrespective of the Mo content in the film. The X-ray diffraction spectrum of film A showed a texture along the 002 orientation, while that of film B showed two peaks, one at θ ≈ 34.5° and the other at ≈ 36.5° corresponding to 002 and 101 orientations, respectively. Film C showed two small peaks corresponding to 100 and 110 orientations. Optical measurements showed that all three films had a transmittance of about 80%. The energy band gap showed a linear increase as Mo concentration increases from 3.29 eV to 3.38 eV. The atomic force microscopy image of film A showed a homogeneous morphology of the surface of the film, while the atomic force microscopy images of films B and C showed an inhomogeneous one.
5
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Content available

Effect of the In-Plane Epitaxial Mismatch between the Substrate and the Film on the Properties of YBa_2Cu_3O_{7-δ} Films

100%
Abal'osheva I., Cieplak M., Adamus Z., Berkowski M., Domukhovski V., Aleszkiewicz M.
Acta Physica Polonica A
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2006
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vol. 109
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issue 4-5
549-554
EN
We study the effect of the in-plane epitaxial mismatch between the substrate and the film on the crystallographic structure and the transport properties of YBa_2Cu_3O_{7-δ} superconducting films of thicknesses ranging between 600 and 3000Å. The films are grown by pulsed laser deposition on the new type of single-crystalline substrates prepared by Czochralski method, with the chemical formula (SrAl_{0.5}Ta_{0.5}O_3)_{0.7}(CaAl_{0.5}Ta_{0.5}O_3)_{0 .1}(LaAlO_3)_{0.2}. We find that superconducting properties of the samples are excellent, and generally they improve with increasing of the film thickness as a result of improved structural ordering. We also investigate the influence of the film thickness on the behavior of the critical current densities.
6
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A Diffusion Model for the Fe_{2}B Layers Formed on a Ductile Cast Iron

100%
Keddam M.
Acta Physica Polonica A
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2018
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vol. 133
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issue 5
1174-1177
EN
In this work, a diffusion model was applied to estimate the boron diffusion coefficients in the Fe_{2}B layers on the ASTM A-536 ductile iron in the temperature range 1173-1273 K by the powder-pack boriding. The mass balance equation at the (Fe_{2}B/substrate) interface was formulated considering the effect of boride incubation times. As a result, the value of activation energy for boron diffusion in the ductile iron was estimated and compared with the literature. To verify the validity of the present model, the experimental Fe_{2}B layer thickness obtained at 1173 K for 10 h was compared to the predicted value. A good concordance was observed between the predicted value of Fe_{2}B layer thickness and the experimental data.
7
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Study of Structure Densification in TiO_2 Coatings Prepared by Magnetron Sputtering under Low Pressure of Oxygen Plasma Discharge

100%
Domaradzki J., Kaczmarek D., Prociow E., Radzimski Z.
Acta Physica Polonica A
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2011
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vol. 120
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issue 1
49-52
EN
Current work presents results of studies on structural and optical properties of the TiO_2 thin films prepared by reactive magnetron sputtering. Oxide thin films were deposited from metallic targets using oxygen gas only instead of usually used mixture of Ar-O_2. Additionally, an increased amplitude of unipolar pulses powering the magnetron has been applied. It is shown that all prepared coatings were stoichiometric and by changing only the discharge voltage it is possible to influence the resulting structural phase and optical properties of prepared thin films. Depending on conditions of magnetron powering, TiO_2 thin films had either the anatase structure with refraction index n = 2.1 (λ = 500 nm) or a high temperature stable rutile structure with n = 2.52 (λ = 500 nm).
8
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Modelling the Boronizing Kinetics in AISI 316 Stainless Steel

100%
Nait Abdellah Z., Keddam M., Elias A.
Acta Physica Polonica A
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2012
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vol. 122
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issue 3
588-592
EN
This work deals with the simulation of the growth kinetics of the (FeB/Fe_2B) bilayer and the diffusion zone on a substrate of AISI 316 stainless steel exposed to the powder-pack boriding process, in the temperature range of 1123-1273 K and a time duration ranging from 2 to 10 h. The developed diffusion model employs a set of mass balance equations at the three growth fronts: [(FeB/Fe_2B), (FeB/diffusion zone) and (diffusion zone/substrate)] under certain assumptions, including the effect of the incubation times during the formation of iron borides and the diffusion zone. For this purpose, a computer code written in Matlab (version 6.5) was created to simulate the boriding kinetics. A good concordance was obtained when comparing the experimental parabolic growth constants taken from the literature and the simulated values of the parabolic growth constants: (k_{FeB}, k_1 and k_2). Moreover, the present model was also used to predict the thicknesses of the FeB and Fe_2B layers and the diffusion zone thickness at various treatment times and boriding temperatures. The simulated values were in good agreement with the experimental borided layers thicknesses.
9
Content available remote

Determination of the Diffusion Coefficients of Boron in the FeB and Fe₂B Layers Formed on AISI D2 Steel

100%
Keddam M., Nait Abdellah Z., Kulka M., Chegroune R.
|
EN
In the present work, a diffusion model was applied to estimate the boron diffusion coefficients in the FeB and Fe₂B layers during the pack-boriding of AISI D2 steel in the temperature range of 1223-1323 K during a variable exposure time between 1 and 8 h. The mass balance equations were formulated at each growing interface by considering the effect of boride incubation times. The estimated values of boron activation energies in the FeB and Fe₂B layers were compared with the literature data. Validation of the present model was made by comparing the experimental thickness of each boride layer, taken from the literature data, with the predicted values. In addition, a simple equation was suggested to estimate the required time to obtain a single Fe₂B layer by diffusion annealing.
10
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Temperature Dependence of Ag Film Roughening during Deposition on Quasicrystal and Approximant Surfaces

100%
Ünal B., Evans J., Thiel P.
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vol. 126
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issue 2
608-612
EN
The temperature (T) dependence of roughening as assessed by scanning tunneling microscopy is compared for growth of Ag films on an 5-fold icosahedral Al-Pd-Mn quasicrystal surface and on an ξ'-approximant. Growth on the quasicrystal corresponds to a version of the Volmer-Weber growth, but modified by quantum size effects, and also by kinetic smoothening at low T and low coverages (θ). Growth on the approximant corresponds to a version of the Stranski-Krastanov growth modified by kinetic roughening at low T and low θ. For larger θ, i.e., for thicker films, distinct behavior is observed.
11
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Structural Characteristics and Optical Properties of Thermally Oxidized Zinc Films

88%
Rusu D., Rusu G., Luca D.
Acta Physica Polonica A
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2011
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vol. 119
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issue 6
850-856
EN
Zinc oxide (ZnO) thin films (with thickness ranged from 780 nm to 1150 nm) were prepared by thermal oxidation in air (at 600-700 K, for 20-30 min) of vacuum evaporated metallic zinc films. The Zn films were deposited on glass substrates at room temperature. The crystalline structure of ZnO thin film samples was investigated using X-ray diffraction technique. The diffraction patterns revealed that the ZnO thin films were polycrystalline and have a wurtzite (hexagonal) structure. The film crystallites are preferentially oriented with (002) planes parallel to substrate surface. Some important structural parameters (lattice parameters of the hexagonal cell, crystallite size, Zn-O bond length, residual stress, etc.) of the films were determined. The surface morphology of the prepared ZnO thin films, investigated by atomic force microscopy, revealed a uniform columnar structure. The spectral dependence of transmission coefficient has been studied in the wavelength range from 300 nm to 1700 nm. The optical energy band gap calculated from the absorption spectra (supposing allowed direct band-to-band transitions) are in the range 3.17-3.19 eV. The dependence of the microstructural and optical characteristics on the preparation conditions (oxidation temperature, oxidation time, etc.) of the oxidized zinc films is discussed.
12
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Influence of Ca Content on the Structure and Properties οf (Co,Ca)O Thin Films Deposited by PLD Technique

75%
Cieniek L., Kac S.
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issue 5
803-807
EN
In this paper the results of investigations of pure and Ca-doped CoO thin films deposited by PLD technique are presented. The studies carried out for variable Ca content allowed to establish optimal conditions for good quality oxide films preparation. The microstructure, chemical/phase composition and morphology of obtained thin films were examined by means of diverse techniques (SEM, EDS, XPS and XRD). For estimation of deposited Ca-doped CoO films quality the nanohardness and scratch tests (adhesion) were performed. Obtained results confirm that using PLD technique it is possible to carry stoichiometric composition of (Co,Ca)O from target to single crystal substrate and allow to conclude that the calcium dopant concentration (chemical composition) influence on the morphology and measured properties of deposited (Co,Ca)O films.
13
Content available remote

Photon-induced switching and tunneling phenomena in a YBCO thin film junction

63%
Yang X., Beckwith A., Miller J.
Open Physics
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2005
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vol. 3
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issue 1
24-34
EN
In the persistent photoconductivity (PPC) phenomenon, illumination of a YBa2Cu3O6.5 thin film junction with a 1mW He−Ne laser leads to the decrease of the critical voltage (similar to the threshold voltage). The decrease of the critical voltage was reversed by illumination with incandescent light. The critical voltage across the junction was experimentally decreased and increased by alternating illumination between He−Ne laser and incandescent light. We also observed visible quenching of the photo-induced state using a 5mW He−Ne laser. Finally, the threshold behavior of the junction was destroyed by illuminating it with incandescent light.
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