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1
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Quantum Spin Hall Effect in Strained (111)-Oriented SnSe Layers

100%
Safaei S., Galicka M., Kacman P., Buczko R.
Acta Physica Polonica A
|
2016
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vol. 129
|
issue 1a
A-150-A-152
EN
Recently, the quantum spin Hall effect has been predicted in (111)-oriented thin films of SnSe and SnTe topological crystalline insulators. It was shown that in these films the energy gaps in the two-dimensional band spectrum depend in an oscillat ory fashion on the layer thickness - the calculated topological invariant indexes and edge state spin polarizations show that for films 20-40 monolayers thick a two-dimensional topological insulator phase appears. Edge states with the Dirac cones with opposite spin polarization in their two branches are obtained for both materials. However, for all but the (111)-oriented SnTe films with an even number of monolayers an overlapping of bands in Γ̅ and M̅ diminishes the final band gap and the edge states appear either against the background of the bands or within a very small energy gap. Here we show that this problem in SnSe films can be removed by applying an appropriate strain. This should enable observation of the quantum spin Hall effect also in SnSe layers.
2
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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
|
2012
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vol. 122
|
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.
3
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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.
Acta Physica Polonica A
|
2015
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vol. 128
|
issue 4
740-745
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.
4
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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
|
2018
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vol. 133
|
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.
5
Content available remote

Influence of Ca Content on the Structure and Properties οf (Co,Ca)O Thin Films Deposited by PLD Technique

75%
Cieniek L., Kac S.
Acta Physica Polonica A
|
2010
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vol. 117
|
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.
6
Content available remote

Effect of Pulsed Laser Power Annealing on Structural and Optical Characteristics of ZnSe Thin Films

75%
Aly S., Akl A., Howari H.
Acta Physica Polonica A
|
2015
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vol. 128
|
issue 3
414-418
EN
Samples of ZnSe of the same film thickness (320 nm) have been thermally evaporated on unheated quartz substrates using high purity powder. The prepared films were subjected to pulsed laser annealing of two different powers. X-ray diffraction studies revealed that the as-deposited samples were polycrystalline cubic (zinc-blende type) structure. As the annealing power increases, the crystallinity of ZnSe films was improved with preferential orientation along the (111) direction parallel to the substrate surface. Microstructural characterizations have been evaluated using the Debye-Scherrer formula. The absorption coefficient as well as the energy gap for the as-deposited and the annealed samples were also reported.
7
Content available remote

Structure and Some Physical Properties of Chemically Deposited Nickel Sulfide Thin Films

63%
Hammad A., ElMandouh Z., Elmeleegi H.
Acta Physica Polonica A
|
2015
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vol. 127
|
issue 4
901-903
EN
Ni₂S_{2-x} thin films with x=0, 0.5, and 1 were prepared by chemical bath deposition technique. Amorphous structure was discovered by XRD for x=1, while α-Ni₇S₆ and NiS phases were discovered for x=0, and x=0.5 respectively. SEM graphs of the studied films have confirmed the XRD results. Optical band gap values increase from 0.845 to 0.912 eV, with increase of the composition x from 0 to 1. Activation energy values increase in the range from x=0 to x=0.5 and does not change for x=1.
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