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Articles de revues sur le sujet « Disorder -Polycrystalline Oxides »

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Auteur : Grafiati

Publié le 7 septembre 2023

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Vahidi, Hasti, Komal Syed, Huiming Guo, Xin Wang, Jenna Laurice Wardini, Jenny Martinez et William John Bowman. « A Review of Grain Boundary and Heterointerface Characterization in Polycrystalline Oxides by (Scanning) Transmission Electron Microscopy ». Crystals 11, n^o 8 (28 juillet 2021) : 878. http://dx.doi.org/10.3390/cryst11080878.

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Interfaces such as grain boundaries (GBs) and heterointerfaces (HIs) are known to play a crucial role in structure-property relationships of polycrystalline materials. While several methods have been used to characterize such interfaces, advanced transmission electron microscopy (TEM) and scanning TEM (STEM) techniques have proven to be uniquely powerful tools, enabling quantification of atomic structure, electronic structure, chemistry, order/disorder, and point defect distributions below the atomic scale. This review focuses on recent progress in characterization of polycrystalline oxide interfaces using S/TEM techniques including imaging, analytical spectroscopies such as energy dispersive X-ray spectroscopy (EDXS) and electron energy-loss spectroscopy (EELS) and scanning diffraction methods such as precession electron nano diffraction (PEND) and 4D-STEM. First, a brief introduction to interfaces, GBs, HIs, and relevant techniques is given. Then, experimental studies which directly correlate GB/HI S/TEM characterization with measured properties of polycrystalline oxides are presented to both strengthen our understanding of these interfaces, and to demonstrate the instrumental capabilities available in the S/TEM. Finally, existing challenges and future development opportunities are discussed. In summary, this article is prepared as a guide for scientists and engineers interested in learning about, and/or using advanced S/TEM techniques to characterize interfaces in polycrystalline materials, particularly ceramic oxides.

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ZHANG, A. M., H. L. CAI, X. S. WU, Z. H. WANG et J. GAO. « PHASE SEPARATION INDUCED BY CATION DISORDER IN (La, Y)2/3(Sr, Ca)1/3MnO3 ». International Journal of Modern Physics B 25, n^o 11 (30 avril 2011) : 1501–9. http://dx.doi.org/10.1142/s0217979211100576.

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Polycrystalline manganite oxides with different A-site cation disorder were synthesized. The hole concentration and average radius of A-site cation are kept unchanged while the A-site cation disorder increases linearly by Y and Sr co-doped in La 2/3 Ca 1/3 MnO 3. All these samples exhibit a paramagnetic insulator to ferromagnetic (FM) metal transition, and the transition temperature T C and T MI decrease while the transition width increases with increasing the A-site cation disorder. T MI is usually 10 K higher than T C for the small cation disorder samples. However, with increasing the cation disorder, T MI is about 60 K lower than T C , and the resistivity increases in magnitude while the magnetization decreases. The metal-to-insulator transition for samples with small cation disorder can be well described by a percolative model, which indicates FM-metal state and antiferromagnetic insulator state assuredly coexist in the transition interval. It reveals that cation disorder suppresses the long-range FM-metal state which results in the phase separation behavior in samples with large cation disorder.

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DEAC, I. G., A. VLĂDESCU, I. BALASZ, A. TUNYAGI et R. TETEAN. « ELECTRICAL AND MAGNETIC BEHAVIOR OF TRANSITION METAL OXIDES Ln0.7A0.3TMO3, Ln= La, Pr ; A = Ca, Sr AND TM = Mn, Co ». International Journal of Modern Physics B 24, n^o 06n07 (20 mars 2010) : 762–69. http://dx.doi.org/10.1142/s0217979210064393.

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We present a detailed magnetic study of the polycrystalline transition metal oxides Ln 0.7 A 0.3 TMO 3, Ln = La , Pr ; A = Ca , Sr and TM = Mn , Co at low temperatures including electrical resistance, magnetization and ac susceptibility measurements. The effect of the A-site and B-site substitutions on the properties of these compounds is discussed. The results of this analysis indicate that the electrical and magnetic behavior of these compounds have some reminiscences of the manganites having similar formula, but the spin disorder and the grain boundary effects control the properties of these materials.

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Marinov, Georgi, Biliana Georgieva, Marina Vasileva et Tsvetanka Babeva. « Study of Structure, Morphology and Optical Properties of Cobalt-Doped and Co/Al-co-Doped ZnO Thin Films Deposited by Electrospray Method ». Applied Sciences 13, n^o 17 (25 août 2023) : 9611. http://dx.doi.org/10.3390/app13179611.

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A versatile electrospray method was utilized for deposition of thin ZnO films doped with Co (5%) (CZO) or co-doped with Co (2.5%) and Al (2.5%) (CAZO). Thin polycrystalline films with approximate thickness of 200 nm and high transmittance (more than 80%) were obtained. No additional XRD peaks due to dopant impurities or dopant oxides were observed. The cobalt doping led to decrease in grain size and increase in crystallite size from 22 nm to 29 nm in the (101) direction. Smaller changes were observed for the CAZO films. Surface roughness of the films was measured using a 3D optical profiler. Surface roughness of the doped films was from 5 nm to 9 nm higher than that of the pure films. Refractive index, extinction coefficient and thickness of the films were calculated using ellipsometric measurements and were further used for determination of optical band gap and Urbach energy. Refractive index and optical band gap increased with doping from 1.86 and 3.29 eV for pure ZnO to 2.00 and 3.35 eV for CZO and 1.97 and 3.33 eV for CAZO films. Through calculation of Urbach energy (119 meV for pure ZnO, 236 meV for CZO and 138 meV for CAZO), it was demonstrated that doping leads to an increase in structural disorder, most pronounced in the case of Co doping.

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Han, Zhiyong, et Zhenzhu Jing. « The Low Temperature Specific Heat of Pr0.65Ca0.35MnO3 ». Advances in Condensed Matter Physics 2014 (2014) : 1–4. http://dx.doi.org/10.1155/2014/394296.

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The low temperature specific heat of polycrystalline perovskite-type Pr0.65Ca0.35MnO3manganese oxide has been investigated experimentally. It is found that the low temperature electron specific heat in zero magnetic field is obviously larger than that of ordinary rare-earth manganites oxide. To get the contribution of phonon to the specific heat precisely, the lattice specific heat is calculated by Debye model fitting. Results confirm that the low temperature specific heat of Pr0.65Ca0.35MnO3is related to the itinerant electrons in ferromagnetic clusters and the disorder in the sample.

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Cohen, Oded, et Zvi Ovadyahu. « 1/f NOISE NEAR THE METAL-INSULATOR TRANSITION ». International Journal of Modern Physics B 08, n^o 07 (30 mars 1994) : 897–903. http://dx.doi.org/10.1142/s0217979294000440.

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The 1/f noise level in polycrystalline indium oxide thin films and of zinc oxide accumulation layers is found to be much higher than that usually observed in metals. A systematic study of the flicker noise properties in these systems reveals a correlation between the 1/f noise magnitude and the proximity of the system to the insulating phase. In fact, the noise appears to increase dramatically close to the Anderson transition but when the average transport properties exhibited by the system are still diffusive. For static disorder that exceeds the critical value characterized by KFl≃1 the system exhibits insulating behavior and the noise level saturates at a rather high, but disorder independent value. The similarity of these findings to the behavior of the magnetic-field-induced Conductance Fluctuations in this system will be pointed out to suggest a common physical origin. This leads to the prediction of high levels of 1/f in all electronic systems that are close to the metal-insulator transition.

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Guillén, Cecilia. « Polycrystalline WO3−x Thin Films Obtained by Reactive DC Sputtering at Room Temperature ». Materials 16, n^o 4 (6 février 2023) : 1359. http://dx.doi.org/10.3390/ma16041359.

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Tungsten oxide thin films have applications in various energy-related devices owing to their versatile semiconductor properties, which depend on the oxygen content and crystalline state. The concentration of electrons increases with intrinsic defects such as oxygen vacancies, which create new absorption bands that give rise to colored films. Disorders in the crystal structure produce additional changes in the electrical and optical characteristics. Here, WO3−x thin films are prepared on unheated glass substrates by reactive DC sputtering from a pure metal target, using the discharge power and the oxygen-to-argon pressure ratio as control parameters. A transition from amorphous to polycrystalline state is obtained by increasing the sputtering power and adjusting the oxygen content. The surface roughness is higher and the bandgap energy is lower for polycrystalline layers than for amorphous ones. Moreover, the electrical conductivity and sub-bandgap absorption increase as the oxygen content decreases.

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OKUDA, TETSUJI, RYOICHI KAJIMOTO, MARIO OKAWA et TOMOHIKO SAITOH. « EFFECTS OF HOLE-DOPING AND DISORDER ON THE MAGNETIC STATES OF DELAFOSSITE CuCrO2 HAVING A SPIN-3/2 ANTIFERROMAGNETIC TRIANGULAR SUBLATTICE ». International Journal of Modern Physics B 27, n^o 05 (21 janvier 2013) : 1330002. http://dx.doi.org/10.1142/s0217979213300028.

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In this review, we will discuss the effects of itinerant hole and disorder produced by substitutions on the magnetic states of polycrystalline delafossite oxide CuCrO 2 having a spin-3/2 antiferromagnetic triangular sublattice. First, we will show the effects of hole-doping by the substitution of nonmagnetic Mg 2+ for magnetic Cr 3+ on the physical properties of CuCrO 2, and will discuss the origin of nontrivial promotion of the 120° Néel state due to the coupling between the itinerant hole and localized spin. Next, we will show the effects of disorder introduced by the isovalent substitutions such as the nonmagnetic Ag + substitution for nonmagnetic Cu + and the nonmagnetic Al 3+ one for magnetic Cr 3+, and will discuss the possibility of appearance of unusual magnetic states such as spin liquid or spin nematic states.

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Zhang, Jiahui, Xujun Su, Yutao Cai, Didi Li, Luhua Wang, Jingjing Chen, Xionghui Zeng, Jianfeng Wang et Ke Xu. « Atomic-resolved structural and electric field analysis of the passivation interface of MIS-HEMTs ». AIP Advances 12, n^o 4 (1 avril 2022) : 045111. http://dx.doi.org/10.1063/5.0087659.

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The passivation interfaces of GaN-based MIS-HEMTs with Si3N4 and ZrO2/Si3N4 bilayers were investigated through atomic resolution scanning transmission electron microscope–energy dispersive spectroscopy–differential phase contrast microscopy methods. It is found that the Si3N4/GaN interface exhibits atomic disorder fluctuation, and the GaN surface is discontinuous at the depth of 1–2 atomic layers. An oxide layer of ∼2 nm is formed at the ZrO2/GaN interface, and the GaN surface is atomically flat. Furthermore, the local minimum of the potential is located at the Si3N4/GaN interface, while it is distributed in the GaN side at the ZrO2/GaN interface. The electric field or potential distribution is affected by the crystal orientation of the polycrystalline ZrO2 layer. Finally, the difference in passivation mechanism is discussed.

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Maaoui, B., Y. Aoun, S. Benramache, A. Nid, R. Far et A. Touati. « Synthesis and Characterization of Physical Properties of the NiO Thin Films by Various Concentrations ». Advances in Materials Science 20, n^o 3 (1 septembre 2020) : 79–87. http://dx.doi.org/10.2478/adms-2020-0017.

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AbstractIn this work, nickel oxide was deposited on a glass substrate at by spray deposition technique; the structural, optical and electrical properties were studied at different NiO concentrations (0.05, 0.10 and 0.15 mol.l−1). Polycrystalline NiO films with a cubic structure with a strong (111) preferred orientation were observed at all sprayed films with minimum crystallite size of 11.97 nm was attained of deposited film at 0.1 mol.l−1. However, α-Ni(OH)2 was observed at 0.15 mol.l−1. The NiO thin films have good transparency in the visible region, the band gap energy varies from 3.54 to 376 eV was affected by NiO concentration, it is shown that the NiO thin film prepared at 0.05 mol.l−1 has less disorder with few defects. The NiO film deposited at 0.15 mol.l−1 has the electrical conductivity was 0.169 (Ω.cm)−1.

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Rossi, Zaid, Bilal Brioual, Abdesamad Aouni, Mustapha Diani et Mohammed Addou. « Microstructural, morphological and optical properties of sprayed thin films of indium doped gadolinium oxide (Gd₂O₃ : In) ». E3S Web of Conferences 336 (2022) : 00041. http://dx.doi.org/10.1051/e3sconf/202233600041.

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This paper featured a study on undoped and Indium doped Gadolinium oxide Gd2O3: In thin films, elaborated on a glass substrates at temperature of 500 °C by homemade Spray Pyrolysis technique, at different Indium concentrations as follow 0, 2, 4, 6 and 8 at %. This thin layers, where a subjects to a numerous characterization techniques to study the effect caused by introducing the dopant element “Indium” in Gadolinium oxide lattice on the structural properties (X-Ray Diffraction and Raman spectroscopy) and optical properties. The structural characterization carried by the X-ray diffraction (XRD) reveals a polycrystalline Monoclinic B-type structure for all Gd2O3:In thin films. Moreover, these findings are verified by the Raman spectroscopy results. Concerning the optical properties of our thin films, the optical measurements carried by UV-VIS-NIR spectrophotometer shows an increase in the transmittance value within the visible region [370-900 nm] and in the band gap energy value by raising Indium doping rate from 0 at % to 6 at %, also the disorder caused inside the thin films were estimated by the Urbach equation. That said, the 2 at % Indium doped gadolinium oxide thin film provides interesting results that can be applied in solar cells as an optical window material.

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Fedotova, J. A. « Electric properties of black arsenic ». Doklady of the National Academy of Sciences of Belarus 66, n^o 1 (9 mars 2022) : 26–34. http://dx.doi.org/10.29235/1561-8323-2022-66-1-26-34.

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R(T, B) of the natural black arsenic (b-As) polycrystal was studied. It was shown that the polycrystalline b-As sample contains the b-As phase and also the traces of its oxide, as well as grey arsenic and arsenolite (As2O3). The behavior of the relative magnetoresistance of the b-As crystal was described by the relation MR(B) = bBn + cBm, where the coefficients b and c and the exponents n and m were also affected by the mechanisms of magnetoresistance formation and temperature. At the temperatures below 10 K, MR(B) shows the presence of a competition between negative (with b < 0 and n ≈ 0.5) and positive (with c > 0 and m ≈ 1) contributions. Above 10 K, only the PMR effect was presented. For the PMR effect, at 10 < T < 100 K it is observed that the values of b > 0, n ≈ 1 and c → 0. Above 100 K, it is observed that the values of b, c > 0 and n ≈ 1 and 1.30 < m < 1.47. The observed behavior of the R(T, B) dependences is associated with strong inhomogeneity and/or disorder of the investigated black arsenic crystal.

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Žurauskienė, Nerija. « Engineering of Advanced Materials for High Magnetic Field Sensing : A Review ». Sensors 23, n^o 6 (8 mars 2023) : 2939. http://dx.doi.org/10.3390/s23062939.

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Advanced scientific and industrial equipment requires magnetic field sensors with decreased dimensions while keeping high sensitivity in a wide range of magnetic fields and temperatures. However, there is a lack of commercial sensors for measurements of high magnetic fields, from ∼1 T up to megagauss. Therefore, the search for advanced materials and the engineering of nanostructures exhibiting extraordinary properties or new phenomena for high magnetic field sensing applications is of great importance. The main focus of this review is the investigation of thin films, nanostructures and two-dimensional (2D) materials exhibiting non-saturating magnetoresistance up to high magnetic fields. Results of the review showed how tuning of the nanostructure and chemical composition of thin polycrystalline ferromagnetic oxide films (manganites) can result in a remarkable colossal magnetoresistance up to megagauss. Moreover, by introducing some structural disorder in different classes of materials, such as non-stoichiometric silver chalcogenides, narrow band gap semiconductors, and 2D materials such as graphene and transition metal dichalcogenides, the possibility to increase the linear magnetoresistive response range up to very strong magnetic fields (50 T and more) and over a large range of temperatures was demonstrated. Approaches for the tailoring of the magnetoresistive properties of these materials and nanostructures for high magnetic field sensor applications were discussed and future perspectives were outlined.

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Jaramillo Palacio, J. A., K. A. Muñoz Pulido, J. Arbey Rodríguez, D. A. Landínez Téllez et J. Roa-Rojas. « Electric, magnetic and microstructural features of the La2CoFeO6 lanthanide ferrocobaltite obtained by the modified Pechini route ». Journal of Advanced Dielectrics 11, n^o 03 (juin 2021) : 2140003. http://dx.doi.org/10.1142/s2010135x21400038.

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In the search for new materials with applicable magnetic properties in spintronic devices, the aim of this work is to report the synthesis of the lanthanide ferrocobaltite La2CoFeO6 using the modified Pechini route; the experimental study of structural, morphological and magnetic properties, and the analysis of the electronic structure and bands are obtained in the framework of the Density Functional Theory. Rietveld refinement of experimental X-ray diffraction patterns revealed the crystallization of this oxide material in a perovskite-like monoclinic structure, space group [Formula: see text]21/[Formula: see text] (# 14). Scanning electron microscopy and atomic force microscopy images revealed that the surface morphology is essentially polycrystalline, with mean grain sizes between 177 and 188 nm. The dispersive X-ray spectroscopy suggests that the material obtained contains La, Fe, Co and O in the stoichiometric proportions expected by up to 98%. The magnetic susceptibility curves as a function of temperature indicated that the material is ordered ferromagnetically, showing strong irreversibility effects due to the disorder of the Fe and Co cations in the three crystallographic directions of the structure and to the strong distortions in the FeO6 and CoO6 octahedra. Magnetic hysteresis curves confirmed the ferromagnetic character of the material for all temperatures evaluated, up to room temperature. I–V response curves revealed a semiconductor-like behavior with a figure of merit exponent 1.53 of the varistor type. The ferromagnetic semiconductor behavior suggests the potential applicability of the material in spintronic technological devices.

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Zhang, Lu, Lixing You, Lei Chen, Wei Peng et Zhen Wang. « Superconductivity of disordered NbN films deposited on Magnesium Oxide and Oxidized Silicon substrates ». Superconductor Science and Technology, 11 août 2022. http://dx.doi.org/10.1088/1361-6668/ac88fd.

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Abstract This study investigates the evolution of superconducting properties as a function of disorder in epitaxial and polycrystalline NbN thin films grown on MgO and SiO2/Si substrates, respectively. By reducing the film thickness from 100 to 4 nm, the effective disorder in these two sets of films encompasses a large range, with the Ioffe-Regel parameter in the range of 5.7–9.3 and 1.5–3.0, respectively. Moreover, the density of states at the Fermi level [N(0)] of epitaxial NbN films decreases from 1.91×1028 to 1.46×1028 states eV−1 m−3 with the superconducting transition temperature (Tc ) ranging from 16.0 to 11.8 K. In contrast, the N(0) of polycrystalline NbN films decreases from 2.18×1028 to 1.80×1028 states eV-1 m-3 with Tc ranging from 14.9 to 2.56 K. The experimental results reveal that the Tc of NbN films with different thicknesses is mainly controlled by N(0), and the greater Coulomb pseudopotential (μ *) in the polycrystalline films leads to lower Tc and larger resistivity. The changes in N(0) and μ * should collectively account for the reduction of Tc with disorder in NbN thin films.

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Vanderah, David J., Jennifer Arsenault, Hongly La, Vitalii Silin, Curtis W. Meuse et Richard S. Gates. « Helical, Disordered, and What that Means : Structural Characterization of a New Series of Methyl 1-Thiaoligo(ethylene Oxide) Self-Assembled Monolayers ». MRS Proceedings 724 (2002). http://dx.doi.org/10.1557/proc-724-n4.5.

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AbstractSelf-assembled monolayers (SAMs) of a series of linear thiols containing a 1-thiaoligo(ethylene oxide) [TOEO] moiety, i.e., HS(CH2CH2O)xCH3, where x = 3 - 6, were prepared on polycrystalline gold (Au) and characterized by reflection absorption infrared spectroscopy (RAIRS) and spectroscopic ellipsometry (SE). For x = 5 and 6, the RAIRS data show that the TOEO segment, oriented normal to the substrate, adopts the highly ordered 7/2 helical structure of the folded-chain crystal polymorph of poly(ethylene oxide). For x = 3 and 4, the RAIRS and SE data indicate disordered, “amorphous” SAMs with essentially no evidence of the helical conformation in the TOEO segment. These data suggest that, for SAMs with TOEO segments, a minimum of five ethylene oxide units is required to adopt a helical conformation.

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