Fabrication Of La0.7Sr0.3MnO3/La0.5Sr0.5CoO3/La0.7Sr0.3MnO3 Heterostructures for Spin Valve Applications

1997 ◽  
Vol 494 ◽  
Author(s):  
M. C. Robson ◽  
S. B. Ogale ◽  
R. Godfrey ◽  
T. Venkatesan ◽  
M. Johnson ◽  
...  
Keyword(s):  
Hysteresis Loop ◽  
Spin Valve ◽  
Ferromagnetic Material ◽  
Perovskite Oxide ◽  
Structural Quality ◽  
X Ray Diffraction ◽  
Metallic Oxide ◽  
Ferromagnetic Layers ◽  
Double Hysteresis Loop

ABSTRACTEpitaxial growth of oxide heterostructures, which may be utilized in spin valve applications, has been demonstrated. The heterostructures consist of two ferromagnetic layers separated by a nonmagnetic metallic interlayer. The ferromagnetic material used is the manganese perovskite oxide, La0.7Sr0.3MnO3, while the metallic oxide interlayer is La0.5Sr0.5CoO3. X-ray diffraction spectra demonstrate the high structural quality of the heterostructures. The magnetization of the heterostructure as a function of magnetic field measured at room temperature yields a double hysteresis loop that is characteristic of this type of spin valve structure. The behavior of this double hysteresis loop is also examined as a function of the metallic interlayer thickness.

scholarly journals Исследование этапов превращения кремния в карбид кремния в процессе атомного замещения методами полного внешнего отражения рентгеновских лучей и рентгеновской дифрактомерии

2022 ◽  
Vol 64 (3) ◽  
pp. 326
Author(s):  
С.А. Кукушкин ◽  
А.В. Осипов ◽  
Е.В. Осипова ◽  
В.М. Стожаров
Keyword(s):  
Structural Quality ◽  
Total External Reflection ◽  
X Rays ◽  
Reflection Method ◽  
X Ray Diffraction ◽  
Modified Technique ◽  
Substitution Method ◽  
X Ray ◽  
Sic Films

X-ray diffraction and total external reflection of X-rays (X-ray reflectometry) methods were used to study the successive stages of synthesis of epitaxial SiC films on Si (100) X-ray diffraction and total external X-ray reflection (XRD) methods were used to study successive stages of synthesis of epitaxial SiC films on Si (100) surfaces, (110) and (111) surfaces by the atom substitution method. The data on the transformation evolution of (100) surfaces were studied, (110) and (111) Si, into SiC surfaces. A comparative analysis of the X-ray structural quality of the SiC layers grown on Si by the atom substitution method with the quality of SiC layers grown by Advanced Epi by the standard CVD method. A modified technique for the total outer X-ray reflection method, based on measurements of the intensity of the reflected X-rays using a special parabolic mirror. It is shown that the method of total external reflection method makes it possible to obtain important information about the degree of surface roughness of SiC layers, the evolution of their crystal structure and plasmon energy in the process of Si to SiC conversion.

Structural and Magnetic Properties of Co50 ± x Pt50 ± x Thin Films Prepared by Mbe Co-Evaporation on (001) MgO Substrate at Various Temperatures

1998 ◽  
Vol 517 ◽  
Author(s):  
V. Parasote ◽  
M.-C. Cadevwlle ◽  
V. Pierron-Bohnes ◽  
W. Grange
Keyword(s):  
Magnetic Properties ◽  
Linear Increase ◽  
Anisotropy Energy ◽  
Structural Quality ◽  
Main Peak ◽  
X Ray Diffraction ◽  
Thermally Activated ◽  
Theoretical Predictions ◽  
Structural And Magnetic Properties

AbstractStructural and magnetic properties of Co50 ± x Pt50± x films 25-50 nm thick, prepared by molecular beam epitaxy onto a Pt buffer grown on MgO (001) substrate have been investigated. A series of 3 samples with different compositions (x = 6, 0, -6) was grown at 800 K on a 10 nm thick Pt buffer and another series of 5 samples of equiatomic composition was prepared at various growth temperatures (390 K≤ TG≤ 780 K) on a Pt buffer 4 nm thick. X-ray diffraction and TEM studies show the presence of grains with [111] and [002] orientations, the [002] grains being a mixture of the tetragonal L10 ordered phase and of the fcc disordered one. Both the thickness of the buffer layer and the deposition temperature are determinant parameters of the structural quality of the films and of the degree of long range order (LRO). An apparent LRO parameter (ηapp) is deduced from the superstructure and main peak intensity ratio. Its increase with the growth temperature is described through a thermally activated model that yields a small activation energy of 0.28 eV, illustrating the role played by both surface diffusion and surface interactions in building the L10 compound in agreement with theoretical predictions. An average uniaxial magnetocrystalline anisotropy energy (Kuav) is deduced from the magnetization curves measured by a SQUID. The anisotropy energy of the [002] grains (Ku002) is deduced, assuming a linear relationship between the anisotropies and the phase percentages. One observes a continuous but not linear increase of Ku002 with ηapp.

Study of the structural quality of heteroepitaxial silicon-on-sapphire structures by high-resolution X-ray diffraction, X-ray reflectivity, and electron microscopy

2014 ◽  
Vol 59 (3) ◽  
pp. 315-322 ◽  
Author(s):  
A. E. Blagov ◽  
A. L. Vasiliev ◽  
A. S. Golubeva ◽  
I. A. Ivanov ◽  
O. A. Kondratev ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Structural Quality ◽  
X Ray Diffraction ◽  
X Ray

INFLUENCE OF Al MONOLAYERS ON THE PROPERTIES OF AlN LAYERS ON Si (111)

2009 ◽  
Vol 16 (01) ◽  
pp. 99-103 ◽  
Author(s):  
L. S. CHUAH ◽  
Z. HASSAN ◽  
H. ABU HASSAN
Keyword(s):  
Buffer Layers ◽  
Structural Quality ◽  
X Ray Diffraction ◽  
X Ray ◽  
Flat Surfaces ◽  
Gan On Si ◽  
Aln Buffer ◽  
Xrd Techniques ◽  
Substrate Temperatures

High-quality aluminum nitride ( AlN ) layers with full width at half maximum (FWHM) values of 11 arcmin were grown by plasma-assisted molecular-beam epitaxy on Si (111) substrates. AlN nucleation layers are being investigated for the growth of GaN on Si . Growth using AlN buffer layers leads to Al -polar films, with surfaces strongly dependent on the flux conditions used. Flat surfaces can be obtained by growing as Al -rich as possible, although Al droplets tend to form. Before starting the AlN growth, a few monolayers of Al are deposited on the substrate to avoid the formation of Si 3 N 4. X-ray diffraction (XRD) techniques were employed to determine the surface and structural quality of the layers. XRD revealed that monocrystalline AlN was obtained. Best AlN films were obtained at high substrate temperatures (875°C) and III/V ratios close to stoichiometry.

Optimization of Distribution Functions for the Hysteresis Preisach Model by Genetic Algorithms

2015 ◽  
Vol 799-800 ◽  
pp. 1330-1338
Author(s):  
Mounir Boudjerda ◽  
Mounir Amir ◽  
Mourad Zergoug ◽  
Siham Azzi ◽  
Mouhamed Sahnoun
Keyword(s):  
Genetic Algorithm ◽  
Hysteresis Loop ◽  
Magnetic Hysteresis ◽  
Ferromagnetic Material ◽  
Distribution Functions ◽  
Preisach Model ◽  
Wide Range ◽  
Material Behaviors ◽  
Hysteresis Modeling

The description of hysteresis is one of the classical problems in magnetic materials. The progress in its solution determines the reliability of modeling and the quality of design of a wide range of contemporary devices, as well as devices that will be created in the future. The intensive investigations in hysteresis modeling were induced by the fact that accuracy models of magnetic hysteresis must be studied yet. In this paper, several identification procedures of the distribution functions of the Preisach model will be investigated by means of a genetic algorithm.The proposed approach has been applied to model the behavior of many samples and distribution functions are optimized which will give accurate results of the hysteresis loop. The results show the robustness and efficiency of genetic algorithm to model the phenomenon of hysteresis loop. This work can give solutions about the ferromagnetic material evaluations and shows the optimization of distribution functions according to the material behaviors.

High Resolution X-ray Diffraction of GaN Grown on Sapphire Substrates

1996 ◽  
Vol 449 ◽  
Author(s):  
A. Saxler ◽  
M. A. Capano ◽  
W. C. Mitchel ◽  
P. Kung ◽  
X. Zhang ◽  
...  
Keyword(s):  
Metalorganic Chemical Vapor Deposition ◽  
Reciprocal Lattice ◽  
Chemical Vapor ◽  
Lattice Points ◽  
Structural Quality ◽  
X Ray Diffraction ◽  
X Ray ◽  
Sapphire Substrates ◽  
Primary Mechanism

ABSTRACTX-ray rocking curves are frequently used to assess the structural quality of GaN thin films. In order to understand the information given by the line shape, we need to know the primary mechanism by which the curves are broadened. The GaN films used in this study were grown by low pressure metalorganic chemical vapor deposition (MOCVD) on (00•1) sapphire substrates. GaN films with both broad and very narrow (open detector linewidth of 40 arcseconds for the (00•2) GaN reflection) rocking curves are examined in this work. Reciprocal space maps of both symmetric and asymmetric reciprocal lattice points are used to determine that the cause of the broadening of GaN rocking curves is a limited in-plane coherence length.

Growth of Well-Aligned ZnO Nanorods Using AuGe Catalyst by Vapor Phase Transportation

2006 ◽  
Vol 6 (11) ◽  
pp. 3624-3627
Author(s):  
S. Y. Ha ◽  
M. N. Jung ◽  
S. H. Park ◽  
H. J. Ko ◽  
H. Ko ◽  
...  
Keyword(s):  
Deep Level ◽  
Zno Nanorods ◽  
Horizontal Tube ◽  
Deep Level Emission ◽  
Structural Quality ◽  
X Ray Diffraction ◽  
Si Substrates ◽  
Uv Emission ◽  
Tilting Angle

Well-aligned ZnO nanorods have been achieved using new alloy (AuGe) catalyst. Zn powder was used as a source material and it was transported in a horizontal tube furnace onto an AuGe deposited Si substrates. The structural and optical properties of ZnO nanorods were characterized by scanning electron microscopy, high resolution X-ray diffraction, and photoluminescence. ZnO nanorods grown at 650 °C on 53 nm thick AuGe layer show uniform shape with the length of 8±0.5 μm and the diameter of 150±5 nm. Also, the tilting angle of ZnO nanorods (±5.5°) is confirmed by HRXRD. High structural quality of the nanorods is conformed by the photoluminescence measurement. All samples show strong UV emission without considerable deep level emission. However, weak deep level emission appears at high (700 °C) temperature due to the increase of oxygen desertion.

Low Pressure Homoepitaxial Growth of 4H-SiC on 4°off-Axis Substrates

2015 ◽  
Vol 821-823 ◽  
pp. 181-184 ◽  
Author(s):  
Ji Chao Hu ◽  
Yu Ming Zhang ◽  
Ren Xu Jia ◽  
Yue Hu Wang ◽  
Bin Xin
Keyword(s):  
Surface Roughness ◽  
Low Pressure ◽  
Structural Quality ◽  
X Ray Diffraction ◽  
Growth Pressure ◽  
Step Bunching ◽  
Homoepitaxial Growth ◽  
Surface Mobility ◽  
The Impact

Step-bunching and triangular defects are significant problems in achieving higher growth rate 4H-SiC epilayers in a horizontal hot wall CVD reactor using a standard non-chlorinated chemistry of silane-propane-hydrogen on 4°off-axis substrates. In this work, the impact of growth pressure on generation of step-bunching and triangular defects and the correlations between the surface roughness and the formation of defects were investigated. It has been found that the impact of growth pressure on concentration of the triangle defects and surface roughness is obviously different. An overall reduction of defects was observed with decreasing growth pressure while the surface roughness increased. The increased adatom surface mobility in low pressure range and minimization of surface free energy are the main reasons for the phenomenon above. High Resolution X-Ray Diffraction (HRXRD) indicated that the structural quality of 4H-SiC epilayers performed at low pressure was higher than that obtained at high pressure.

Normal Incidence Photoresponse as a Function of Well Width in P-Type GaAs/AlGaAs Multi-Quantum Wells

1996 ◽  
Vol 450 ◽  
Author(s):  
G. J. Brown ◽  
M. A. Capano ◽  
S. M. Hegde ◽  
K. Eyink ◽  
F. Szmulowicz
Keyword(s):  
Quantum Well ◽  
Quantum Wells ◽  
Normal Incidence ◽  
Light Hole ◽  
Structural Quality ◽  
Hole State ◽  
X Ray Diffraction ◽  
Optimization Study ◽  
P Type

ABSTRACTWe have performed an optimization study of the mid-infrared photoresponse of p-type GaAs/AlGaAs Quantum Well Infrared Photodetectors (QWIPs) designed for normal incidence detection. In these p-type quantum wells, normal incidence absorption is allowed (by the dipole selection rules for optical transitions) especially for transitions from the heavy-hole ground state to the second light-hole state. Previous theoretical modeling predicted that this transition will produce the strongest bound-to-continuum infrared absorption when the second light-hole state is located very near the top of the GaAs quantum well. For AlGaAs barrier layers with 30% aluminum, our modeling showed that a well width between 45Å and 50Å would optimize the normal incidence photoresponse of this p-type QWIP. In this work, photore^oonse spectra are reported for well widths ranging from 40Å to 65Å. A series of samples were tudied in which only the GaAs well width was varied in two monolayer increments, from 11 to 20 monolayers. Photoluminescence and X-ray diffraction measurements were used to verify the composition, well width, and structural quality of each sample. This study verified that the spectral range of the normal incidence photoresponse is narrower, as predicted by theory, for well widths in which the second light-hole state approaches the top of the valence band well.

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