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Afre, Rakesh A., Nallin Sharma, Maheshwar Sharon et Madhuri Sharon. « Transparent Conducting Oxide Films for Various Applications : A Review ». REVIEWS ON ADVANCED MATERIALS SCIENCE 53, no 1 (1 janvier 2018) : 79–89. http://dx.doi.org/10.1515/rams-2018-0006.
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Abstract This review encompasses properties and applications of polycrystalline or amorphous, Transparent Conducting Oxides (TCO) semiconductors. Coexistence of electrical conductivity and optical transparency in TCO depends on the nature, number and atomic arrangements of metal cations in oxides, on the resident morphology and presence of intrinsic or introduced defects. Therefore, TCO semiconductors that are impurity-doped as well as the ternary compounds and multi-component oxides consisting of combinations are discussed. Expanding use of TCO is endangered by scarcity, cost of In, fragility of glass, limited transparency to visible light, instability above >200 °C, non-flexible for application of flexible solar cell; thus driving search for alternatives such as graphene or CNT, that are more stable under acidic, alkaline, oxidizing, reducing and elevated temperature. There are reasons to conclude that there is need to develop large area deposition techniques to produce TCO films with high deposition rate. TCOs are mostly n-type semiconductors, but p-type are also being researched
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Liu, Jun, Jin Liang He, Jun Hu, Wang Chen Long et Feng Chao Luo. « Admittance Spectroscopy of Y2O3-Doped ZnO Varistors Sintered at Different Temperature ». Key Engineering Materials 434-435 (mars 2010) : 382–85. http://dx.doi.org/10.4028/www.scientific.net/kem.434-435.382.
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ZnO varistors are multicomponent polycrystalline ceramics with highly nonlinear current-voltage characteristics and surge energy absorption capabilities. The voltage gradient of the ZnO varistor is inversely proportional to its average grain size. Recently, the rare-earth oxides have been reported as growth inhibitor of ZnO grains to obtain high voltage gradient. Although the dopant of rare-earth oxides can remarkably enhance the voltage gradients of varistor samples, their leakage currents and nonlinear coefficients deteriorate at the same time. In this paper, the sintering effects on electrical characteristics and admittance spectroscopies of ZnO varistor samples doped with yttrium oxides were investigated. Samples were fabricated under different sintering temperatures, including 1000 °C, 1100 °C, 1200 °C and 1300 °C. Then, the electrical characteristics and admittance spectroscopies of these varistor samples were measured. The measured current-voltage results behave special U-type curves related to sintering temperature. Furthermore, the admittance spectroscopy of these samples revealed the sintering effects on the intrinsic defects of ZnO varistors.
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Shcherbakov I. P., Narykova M. V. et Chmel A. E. « Evolution of structural defects of SiO-=SUB=-2-=/SUB=--TiO-=SUB=-2-=/SUB=- glasses with a change in TiO-=SUB=-2-=/SUB=- concentration from zero to phase separation ». Physics of the Solid State 65, no 4 (2023) : 588. http://dx.doi.org/10.21883/pss.2023.04.55999.20.
Texte intégralRésumé :
The thermal expansion coefficient (TEC) of binary glasses SiO2-TiO2 decreases as the TiO2 concentration grows. At concentration of TiO2 in the range of 4-6 mol% (in dependence of the applied synthesis method) TEC becomes negative; at concentration of 8-11 mol% devitrification occurs. A combination of photoluminescence (PL) and IR reflection techniques were applied for studying the evolution of point and structural defects in the range of TiO2 concentration from zero to phase separation. The precision measurements of density showed its drop at TiO2 content of 7.9 mol% thus evidencing the conversion of glass into a polycrystalline substance consisting of SiO2 and TiO2 crystallites. In the TiO2 concentration range of compatibility of oxides, an ensemble of point defects comprises =SiO-Si= and =Ti-O- centers as well as =Si-Si= and =Si-Ti= neutral oxygen-vacancies. At the dopant concentration specific for phase separation (TiO2 7.9 mol%), the PL-active groups of =Si-Ti= go away, while the IR-detectable Si-O-Ti bridges remain stable. Keywords: SiO2-TiO2 glass, point defects, structural defects, photoluminescence, IR spectroscopy.
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Samb, Mamadou Lamine, Emmanuel Jacques, Amadou Seidou Maiga et Tayeb Mohammed-Brahim. « Benefits from Using Very Thin Channel Layer for TFTs ». Electronics 12, no 12 (16 juin 2023) : 2694. http://dx.doi.org/10.3390/electronics12122694.
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It is known from many published data on amorphous or polycrystalline silicon and on metal oxides based Thin Film Transistors (TFTs) that their electrical parameters improve when decreasing the thickness of the channel layer. The origin of this improvement is discussed here through electrostatic arguments only. In particular, it is shown that the behavior of the subthreshold swing with the thickness does not depend on the type of materials. The material and its electrical defects determine only the importance of the improvement but not the trend towards better electrical parameters. Meanwhile, in general, the electrical stability under gate stress enhances too. The improved stability is explained by the reduced electronic charge inside the channel layer, leading to a lower injection of electrons in the gate insulator.
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Lee, Ming-Kwei, et Chih-Feng Yen. « Comprehension of Postmetallization Annealed MOCVD-TiO2on(NH4)2STreated III-V Semiconductors ». Active and Passive Electronic Components 2012 (2012) : 1–10. http://dx.doi.org/10.1155/2012/148705.
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The electrical characteristics of TiO2films grown on III-V semiconductors (e.g., p-type InP and GaAs) by metal-organic chemical vapor deposition were studied. With (NH4)2S treatment, the electrical characteristics of MOS capacitors are improved due to the reduction of native oxides. The electrical characteristics can be further improved by the postmetallization annealing, which causes hydrogen atomic ion to passivate defects and the grain boundary of polycrystalline TiO2films. For postmetallization annealed TiO2on (NH4)2S treated InP MOS, the leakage current densities can reach2.7×10−7and2.3×10−7 A/cm2at±1 MV/cm, respectively. The dielectric constant and effective oxide charges are 46 and1.96×1012 C/cm2, respectively. The interface state density is7.13×1011 cm−2eV−1at the energy of 0.67 eV from the edge of valence band. For postmetallization annealed TiO2on (NH4)2S treated GaAs MOS, The leakage current densities can reach9.7×10−8and1.4×10−7at±1 MV/cm, respectively. The dielectric constant and effective oxide charges are 66 and1.86×1012 C/cm2, respectively. The interface state density is5.96×1011 cm−2eV−1at the energy of 0.7 eV from the edge of valence band.
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Afonin, Nikolay N., et Vera A. Logachova. « Reactive Interdiffusion of Components in a Non-Stoichiometric Two‑Layer System of Polycrystalline Titanium and Cobalt Oxides ». Kondensirovannye sredy i mezhfaznye granitsy = Condensed Matter and Interphases 22, no 4 (26 novembre 2020) : 430–37. http://dx.doi.org/10.17308/kcmf.2020.22/3058.
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We demonstrated the possibility of using the mathematical form of Darken's theory, applied to the description of the Kirkendall effect in binary systems, to the description of reactive interdiffusion in non-stoichiometric polycrystalline film oxide systems with limited solubility. The aim of the study was the simulation of reactive interdiffusion under vacuum annealing of a thin film system consisting of two non-stoichiometric polycrystalline titanium and cobalt oxides. The nonstoichiometric nature of the system assumes the presence of mobile components, free interstitial cobalt and titanium cations in it. Phase formation occurs as a result of reactive interdiffusion and trapping of mobile components of the systemon inter-grain traps. The proposed mechanism describes the formation of complex oxide phases distributed over the depth of the system.A complex empirical research technique was used, involving Rutherford backscattering spectrometry, X-ray phase analysis and modelling methods. The values of the characteristic parameters of the process were determined by numerical analysis of the experimentally obtained distributions of the concentrations of the components within the developed model. During vacuum annealing of a thin film two-layer system of non-stoichiometric TiO2–x–Co1–уO oxides in temperature range T = 773 – 1073 К, the values of the individual diffusion coefficients of cobalt DCo = 5.1·10–8·exp(–1.0 eV/(kT) cm2/s and titaniumDTi = 1.38·10–13·exp(–0.31 eV/(kT) cm2/s were determined.It was shown that for T = 1073 K, the phase formation of CoTiO3 with a rhombohedral structure occurs. The extension of the phase formation region of complex cobalt and titanium oxides increases with an increase in the vacuum annealing temperature and at 1073 K it is comparable with the total thickness of the film system.The model allows predicting the distribution of the concentrations of the components over the depth of multilayer nonstoichiometric systems in which reactive interdiffusion is possible.
References1. Chebotin V. N. Fizicheskaya khimiya tverdogo tela[Physical chemistry of a solid state]. Moscow: KhimiyaPubl.; 1982. 320 p. (in Russ.)2. Tretyakov Yu. D. Tverdofaznye reaktsii [Solidphase reactions]. Moscow: Khimiya Publ.; 1978. 360 p.(in Russ.)3. Afonin N. N., Logacheva V. A. Interdiffusion andphase formation in the Fe–TiO2 thin-film system.Semiconductors. 2017;51(10): 1300–1305. DOI: https://doi.org/10.1134/S10637826171000254. Afonin N. N., Logacheva V. A. Cobalt modificationof thin rutile films magnetron-sputtered in vacuumtechnical. Technical Physics, 2018;63(4): 605–611. DOI:https://doi.org/10.1134/S10637842180400235. Afonin N. N., Logacheva V. A. Modeling of thereaction interdiffusion in the polycrystalline systemswith limited component solubility. IndustrialLaboratory. Diagnostics of Materials. 2019;85(9): 35–41.DOI: https://doi.org/10.26896/1028-6861-2019-85-9-35-41diffusion (In Russ., abstract in Eng.)6. Afonin N. N., Logacheva V. A. Modeling ofinterdiffusion and phase formation in the thin-filmtwo-layer system of polycrystalline oxides titaniumand cobalt. Kondensirovannye sredy i mezhfaznyegranitsy = Condensed Matter and Interphases.2019;21(3): 358–365. DOI: https://doi.org/10.17308/kcmf.2019.21/1157 (In Russ., abstract in Eng.)7. Darken L. S. Diffusion, mobility and theirinterrelation through free energy in binary metallicsystems. Trans. AMIE.1948;175: 184–190.8. Gurov K. P., Kartashkin B. A., Ugaste Yu. E.Vzaimnaya diffuziya v mnogofaznykh metallicheskikhsistemakh [Interdiffusion in multiphase metallicsystems]. Moscow: Nauka Publ.; 1981. 350 p. (In Russ.)9. Kulkarni N. S., Bruce Warmack R. J., RadhakrishnanB., Hunter J. L., Sohn Y., Coffey K. R., …Belova I. V. Overview of SIMS-based experimentalstudies of tracer diffusion in solids and application toMg self-diffusion. Journal of Phase Equilibria andDiffusion. 2014;35(6): 762–778. DOI: https://doi.org/10.1007/s11669-014-0344-410. Aleksandrov O. V., Kozlovski V. V. Simulationof interaction between nickel and silicon carbideduring the formation of ohmic contacts. Semiconductors.2009;43(7): 885–891. DOI: https://doi.org/10.1134/S106378260907010011. Kofstad P. Nonstoichiometry, diffusion, andelectrical conductivity in binary metal oxides. Wiley-Interscience; 1972. 382 p.12. Bak T., Nowotny J., Rekas M., Sorrell C. C. Defectchemistry and semiconducting properties of titaniumdioxide: II. Defect diagrams. Journal of Physics andChemistry of Solids. 2003;64(7): 1057–1067. DOI:https://doi.org/10.1016/s0022-3697(02)00480-813. Iddir H., Öğüt,S., Zapol P., Browning N. D.Diffusion mechanisms of native point defects in rutileTiO2: Ab initio total-energy calculations. PhysicalReview B. 2007;75(7): DOI: https://doi.org/10.1103/physrevb.75.07320314. Hoshino K., Peterson N. L., Wiley C. L. Diffusionand point defects in TiO2–x. Journal of Physics and Chemistry of Solids. 1985;46(12): 1397-1411. DOI:https://doi.org/10.1016/0022-3697(85)90079-415. Fiebig J., Divinski S., Rösner H., Estrin Y.,Wilde G. Diffusion of Ag and Co in ultrafine-graineda-Ti deformed by equal channel angular pressing.Journal of Applied Physics. 2011;110(8): 083514. DOI:https://doi.org/10.1063/1.365023016. Straumal P. B. Stakhanova S. V., Wilde G.,Divinski S. V. 44Ti self-diffusion in nanocrystalline thinTiO2 films produced by a low temperature wet chemicalprocess. Scripta Materialia. 2018;149: 31–35. DOI:https://doi.org/10.1016/j.scriptamat.2018.01.02217. Patrick R. Cantwell, Ming Tang, Shen J. Dillon,Jian Luo, Gregory S. Rohrer, Martin P. Harmer. Grainboundary complexions. Acta Materialia. 2014;62: 1–48.DOI: https://doi.org/10.1016/j.actamat.2013.07.03718. Dillon S. J., Tang M., Carter W. C., Harmer M. P.Complexion: A new concept for kinetic engineering inmaterials science. Acta Materialia, 2007;55(18):6208–6218. DOI: https://doi.org/10.1016/j.actamat.2007.07.02919. Grain boundary complexion transitions inWO3- and CuO-doped TiO2 bicrystals. Acta Materialia.2013;61(5); 1691–1704. DOI: https://doi.org/10.1016/j.actamat.2012.11.04420. Nie J., Chan J. M., Qin M., Zhou N., Luo J.Liquid-like grain boundary complexion and subeutecticactivated sintering in CuO-doped TiO2. ActaMaterialia. 2017;130: 329–338. DOI: https://doi.org/10.1016/j.actamat.2017.03.037
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Щербаков, И. П., М. В. Нарыкова et А. Е. Чмель. « Эволюция дефектов строения стекол SiO-=SUB=-2-=/SUB=--TiO-=SUB=-2-=/SUB=- при изменении концентрации TiO-=SUB=-2-=/SUB=- от нуля до разделения фаз ». Физика твердого тела 65, no 4 (2023) : 604. http://dx.doi.org/10.21883/ftt.2023.04.55297.20.
Texte intégralRésumé :
The thermal expansion coefficient (TEC) of binary glasses SiO 2 -TiO 2 decreases as the TiO 2 concentration grows. At concentration of TiO 2 in the range of 4–6 mol% (in dependence of the applied synthesis method) TEC becomes negative; at concentration of 8–11 mol% devitrification occurs. A combination of photoluminescence (PL) and IR reflection techniques were applied for studying the evolution of point and structural defects in the range of TiO 2 concentration from zero to phase separation. The precision measurements of density showed its drop at TiO 2 content of 7.9 mol% thus evidencing the conversion of glass into a polycrystalline substance consisting of SiO 2 and TiO 2 crystallites. In the TiO 2 concentration range of compatibility of oxides, an ensemble of point defects comprises ≡Si–O – and ≡Ti–O – centers as well as ≡Si–Si≡ and ≡Ti–Ti≡ neutral oxygen-vacancies. At the dopant concentration specific for phase separation (7.9 mol%), the PL-active groups of Si–Ti go away, while the IR-detectable Si–O–Ti bridges remain stable.
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Zhang, Yue Bin, Thirumany Sritharan et Sean Li. « Isolated and Grouped Co Spins in Polycrystalline Zn1-xCoxO Oxides ». Advances in Science and Technology 52 (octobre 2006) : 27–30. http://dx.doi.org/10.4028/www.scientific.net/ast.52.27.
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Polycrystalline stoichiometric Co-substituted ZnO oxides have been synthesized by solid state reaction via sintering ZnO and Co powders in air. The precise nature of magnetic coupling is determined by studying carefully structural and magnetic properties. The magnetization as a function of temperature for Zn1-xCoxO (x = 0.02, 0.05, 0.0625 and 0.10) can be fitted well to a model with a paramagnetic Curie term, an antiferromagnetic Curie-Weiss term and a diamagnetic constant, which could arise from spins of isolated Co ions, grouped Co ions that are in nearest neighbor positions and a diamagnetic background, respectively. The substitution of Co at the Zn sites does not occur in a completely random manner but the Co ions appear to have a tendency for grouping. It is interesting to note in Raman measurements that host lattice defects with 2 distinct impurity modes may be induced by isolated and grouped Co spins.
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Qi, Yue, Christine James, Tridip Das, Jason D. Nicholas, Leah Nation et Brian W. Sheldon. « (Invited) Computing the Anisotropic Chemical Strain in Non-Stoichiometric Oxides for Solid Oxide Fuel Cell and Li-Ion Battery Applications ». ECS Meeting Abstracts MA2018-01, no 32 (13 avril 2018) : 1940. http://dx.doi.org/10.1149/ma2018-01/32/1940.
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Accurate characterization of chemical strain is required to study a broad range of chemical-mechanical coupling phenomena. By combining density functional theory (DFT) calculations and elastic dipole tensor theory, it is readily to predict the long-range chemical strain tensor and the chemical expansion coefficient tensor induced by dilute point defects in a crystal structure. First, we demonstrate that, even in cubic CeO2-δ, both the short-range deformation surrounding an oxygen vacancy and the long-range chemical strain (or the expansion coefficient) are anisotropic. The origin of this anisotropy is the charge disproportionation between the four cerium atoms surrounding each oxygen vacancy (two become Ce3+ and two become Ce4+) when a neutral oxygen vacancy is formed. While the short-range deformation agrees with experimentally determined Ce-O bond lengths, the predicted maximum and average chemical strains successfully bound the variety of CeO2-δ chemical strain behavior previously reported in the literature. Normally, since there are six possible disproportionation configurations, the average chemical strain is isotropic. Only under an external bias, such as an applied electric field, the chemical strain can be oriented to show the anisotropic effect. This successfully explained the giant electrostriction effect reported in doped and un-doped CeO2-δ. Next, we show strains induced by coupled vacancies in layered Li-intercalation compounds for battery applications. Li2MnO3 was investigated as Li-excess intercalation compounds containing Li2MnO3 need to be “activated” to deliver the high capacity. This activation process during the first delithiation cycle at a high voltage is believed to introduce oxygen vacancies into the system. Due to the large amount Li vacancy generated, a large number of defect configurations were sampled and the average chemical strain induced by Li vacancy concentration is obtained by Boltzmann average. Previously, we have demonstrated that it is energetically favorable to create a Li-O-Li vacancy dumbbell structure (VLi - VO - VLi) in Li2MnO3. The chemical strain of the vacancy dumbbell structure is smaller than the sum of the chemical strain of one Vo and two VLis. The chemical expansion coefficient averaged for the polycrystalline samples and the experimentally measured stress change provided a novel method to in situ track the irreversible chemical changes in Li-excess cathode materials.
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Chen, Nan, S. J. Rothman, J. L. Routbort et K. C. Goretta. « Tracer diffusion of Ba and Y in YBa2Cu3Ox ». Journal of Materials Research 7, no 9 (septembre 1992) : 2308–16. http://dx.doi.org/10.1557/jmr.1992.2308.
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Tracer self-diffusion of Ba and Y and the diffusion of Dy, Ho, and Gd, which substitute for Y, have been measured in polycrystalline YBa2Cu3Ox over temperature and oxygen partial pressure ranges of 850 to 980 °C and 103 to 105 Pa, respectively. The diffusion of Ba is slower than that of oxygen or copper, with a high activation energy of about 890 ± 80 kJ/mole. Large anisotropy has also been observed, with diffusion along the c-axis being more than three orders of magnitude slower than diffusion in randomly oriented polycrystals. Diffusion coefficients of Ba were, within experimental uncertainty, independent of oxygen partial pressure over the range measured. The diffusion coefficients of the Y-site species were nearly identical and an activation energy of about 1.0 MJ/mole was estimated, in agreement with that for high-temperature deformation. Attempts to speed up the kinetics through creation of point defects on the Y site by doping proved to be unsuccessful. These results are compared to cation diffusion in cubic perovskites and simple oxides.
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Yu, Shijin, Wenzhen Zhu, Ying Wei, Jiahao Tong, Quanya Wei, Tianrui Chen, Xuannan He, Dingwen Hu, Cuiyun Li et Hua Zhu. « Facile Synthesis of Multi-Channel Surface-Modified Amorphous Iron Oxide Nanospheres as High-Performance Anode Materials for Lithium-Ion Batteries ». Energies 15, no 16 (18 août 2022) : 5974. http://dx.doi.org/10.3390/en15165974.
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Based on the synergistic effect of ripening and hydrogen ion etching in a hydrothermal solution, a simple, facile, and low-cost new strategy was demonstrated to prepare multi-channel surface-modified amorphous Fe2O3 nanospheres as anodes for Li-ion batteries in this study. Compared with polycrystalline Fe2O3, the conversion reaction between amorphous Fe2O3 and lithium ions has a lower Gibbs free energy change and a stronger reversibility, which can contribute to an elevation in the cycle capability of the electrode. Meanwhile, there are abundant active sites and more effective dangling bonds/defects in amorphous materials, which is beneficial to promote charge transfer and lithium-ion migration kinetics. The Galvanostatic intermittent titration analysis results confirmed that the amorphous Fe2O3 electrode had a higher Li+ diffusion coefficient. In addition, the surfaces of the amorphous nanospheres are corroded to produce multiple criss-cross channels. The multi-channel surface structure can not only increase the contact area between Fe2O3 nanospheres and electrolyte, but also reserve space for volume expansion, thereby effectively alleviating the volume change during the intercalation-deintercalation of lithium ions. The electrochemical performance showed that the multi-channel surface-modified amorphous Fe2O3 electrode exhibited a higher specific capacity, a more stable cycle performance, and a narrower voltage hysteresis. It is believed that amorphous metal oxides have great potential as high-performance anodes of next-generation lithium-ion batteries.
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Adamchuck, D. V., et V. K. Ksenevich. « Control of Electrical and Optical Parameters of Humidity Sensors Active Elements Based on Tin Oxides Films with Variable Composition ». Devices and Methods of Measurements 10, no 2 (24 juin 2019) : 138–50. http://dx.doi.org/10.21122/2220-9506-2019-10-2-138-150.
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The aim of this work is development of technique for synthesis of tin oxides films with various stoichiometric composition, characterized by high electrical conductivity and light transmittance in the UV and visible range of the electromagnetic spectrum, for their further application as humidity and gas sensors, as well as electrodes for electro-and photocatalytic converters.Nonstoichiometric SnO/SnO2 /SnO2−δ films were synthesized by reactive magnetron sputtering of tin onto glass substrates in argon plasma with oxygen addition and with subsequent thermal oxidation of the formed layers in air. To change the structural, optical, and electrical properties of the films and to find out the optimal synthesis parameters, the oxygen content during the deposition process and the annealing temperature in air were varied in the range of 0–2 vol. % and of 200–450 °C, respectively. The characterization of the films was carried out using a 4-probe method for measuring the electrical resistance, X-ray diffraction, and optical spectroscopy of light transmission.As a result of a comprehensive analysis of the structural, optical and electrical properties of the films, it was found that the optimal synthesis parameters to obtain the most transparent and conductive coatings promising for use as humidity, gas sensors and in photovoltaic devices are the following: oxygen content in argon plasma during sputtering process is ≈ 0,8–1,2 vol. %, the annealing temperature in air is ≈ 350–375 °C. In this case a polycrystalline film with high electrical conductivity and high transmittance in the visible and UV regions of the electromagnetic spectrum with prevailing of tin dioxide phase with structural defects (oxygen vacancies) is formed.
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Cao, Qing. « (Invited) Two-Dimensional Amorphous Carbon Prepared from Solution Precursor As Novel Dielectrics for Nanoelectronics ». ECS Meeting Abstracts MA2022-01, no 9 (7 juillet 2022) : 755. http://dx.doi.org/10.1149/ma2022-019755mtgabs.
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Low-dimensional electronic materials such as carbon nanotubes, graphene, and transition-metal chalcogenides have drawn a lot of interest from the aspects of both fundamental studies and practical applications. Their atomic-scale thickness and unique electrical properties make them become promising candidates as the drop-in replacement of conventional bulk electronic materials in future electronic devices to enable better performance and enhanced functionality. Research on low-dimensional electronic materials so far has predominantly focused on crystalline semimetals and semiconductors. However, advanced electronic devices also require suitable low-dimensional insulators, which are ideally in the highly disordered amorphous form, similar as SiO2 for silicon, to avoid the nonuniformity and defects related with grain boundaries, in order to fulfill their potentials. Here we present a new strategy for the solution-based preparation of atomically thin amorphous carbon as a novel 2D insulator. Our unique process can precisely control the film thickness at atomic level and has excellent scalability toward wafer-scale deposition. The obtained 2D amorphous carbon monolayer exhibits mechanical robustness comparable to graphene and can be suspended as a free-standing membrane on transmission-electron-microscopy grid, allowing the structural characterization down to atomic resolution. The structure-property relationship for such amorphous materials at 2D limit was then established based on a combination of experiment and density-functional theory simulation. The unique physical properties of 2D amorphous carbon suggest it as a promising candidate to accompany crystalline low-dimensional semiconductors and semimetals in future nanoelectronic devices, and its performance advantages over conventional 3D metal oxides and polycrystalline 2D insulators were verified in experiment : Serving as the gate dielectric in graphene transistors, the absence of grain boundaries in 2D amorphous carbon allows us to aggressively reduce the gate-dielectric thickness down to merely three-atomic layers to enhance the capacitance coupling between the gate and the channel, while still maintaining a low leakage current density below 10-4 A/cm2, which is many orders of magnitude lower compared to the leakage current across the polycrystalline hexagonal boron nitride with the same thickness. Meanwhile, the perfectly clean van der Waals interface it forms with the graphene channel leads to the sharply reduction of the device hysteresis and thus average effective mobility twice as high as that of devices built with bulk SiO2 as gate dielectric. Serving as the switching medium in resistive random access memory cells, the atomic-level thinness of the 2D amorphous carbon enables low operating voltage below 0.4 V, fast switching time <20 ns, and low energy consumption per write operation below 20 fJ, together with excellent endurance (>104) and data retention (>10 years @ 85oC). Moreover, its atomic structural heterogeneity provides well defined ion-transport pathways as suggested in ab initio simulations, leading to the drastically improved device-to-device and cycle-to-cycle uniformity with the standard deviation of Set/Reset voltages below 50 mV in experiment, which is among the lowest values ever reported for memristors. The concurrent achievement of all these performance metrics has not been accomplished with memristors built on either bulk oxides or polycrystalline 2D materials.
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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, no 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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Kim, Sunjae, Minje Kim, Jihyun Kim et Wan Sik Hwang. « Plasma Nitridation Effect on β-Ga2O3 Semiconductors ». Nanomaterials 13, no 7 (28 mars 2023) : 1199. http://dx.doi.org/10.3390/nano13071199.
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The electrical and optoelectronic performance of semiconductor devices are mainly affected by the presence of defects or crystal imperfections in the semiconductor. Oxygen vacancies are one of the most common defects and are known to serve as electron trap sites whose energy levels are below the conduction band (CB) edge for metal oxide semiconductors, including β-Ga2O3. In this study, the effects of plasma nitridation (PN) on polycrystalline β-Ga2O3 thin films are discussed. In detail, the electrical and optical properties of polycrystalline β-Ga2O3 thin films are compared at different PN treatment times. The results show that PN treatment on polycrystalline β-Ga2O3 thin films effectively diminish the electron trap sites. This PN treatment technology could improve the device performance of both electronics and optoelectronics.
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PACCHIONI, GIANFRANCO. « QUANTUM CHEMISTRY OF OXIDE SURFACES : FROM CO CHEMISORPTION TO THE IDENTIFICATION OF THE STRUCTURE AND NATURE OF POINT DEFECTS ON MgO ». Surface Review and Letters 07, no 03 (juin 2000) : 277–306. http://dx.doi.org/10.1142/s0218625x00000336.
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The electronic structure and chemisorption properties of the surface of ionic crystals are reviewed, with emphasis on two topics: a critical overview of the experimental and theoretical studies of the adsorption of CO on single crystal and polycrystalline MgO, and a discussion on the most important defect centers at the MgO surface — low-coordinated sites, single oxygen and magnesium vacancies, divacancies, and impurity or substitutional atoms. The two subjects are to some extent interconnected. From the detailed theoretical and experimental study of the adsorption of a nonreactive molecule like CO and from the comparison of experiments done on single crystal or thin films and on powder samples, one can learn about the nature and concentration of the defects at the surface. A more precise characterization of defects requires, however, a careful spectroscopic investigation and a direct comparison with quantum-chemical calculations of both geometric structure and observable properties. The combined theoretical–experimental approach offers new opportunities for a better understanding of the complexity of oxide surfaces.
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Magari, Yusaku, Taiki Kataoka, Wenchang Yeh et Mamoru Furuta. « (Invited) Hydrogenated Polycrystalline In2O3 (In2O3:H) Thin-Film Transistor with High Mobility Exceeding 100 cm2V−1s−1 Via Solid-Phase Crystallization ». ECS Meeting Abstracts MA2022-02, no 35 (9 octobre 2022) : 1277. http://dx.doi.org/10.1149/ma2022-02351277mtgabs.
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Oxide semiconductors have been extensively studied as active channel layers of thin-film transistors (TFTs) for electronic applications. However, the field-effect mobility (μ FE) of oxide TFTs is not sufficiently high to compete with that of low-temperature-processed polycrystalline-Si TFTs (50–100 cm2V−1s−1). Here, we propose a simple process to obtain high-performance TFTs, namely hydrogenated polycrystalline In2O3 (In2O3:H) TFTs grown via the low-temperature solid-phase crystallization (SPC) process. In2O3:H TFTs fabricated at 300 °C exhibit superior switching properties with µ FE = 139.2 cm2V−1s−1. The hydrogen introduced during sputter deposition plays an important role in enlarging the grain size and decreasing the subgap defects in SPC-prepared In2O3:H. The proposed method does not require any additional expensive equipment and/or change in the conventional oxide TFT fabrication process. We believe these SPC-grown In2O3:H TFTs have a great potential for use in future electronic applications.
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Tsch�pe, Andreas. « Interface Defect Chemistry and Effective Conductivity in Polycrystalline Cerium Oxide ». Journal of Electroceramics 14, no 1 (janvier 2005) : 5–23. http://dx.doi.org/10.1007/s10832-005-6580-6.
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Chiesa, Mario, Maria Cristina Paganini, Elio Giamello et Damien M. Murphy. « Partial Ionization of Cesium Atoms at Point Defects over Polycrystalline Magnesium Oxide ». Journal of Physical Chemistry B 105, no 43 (novembre 2001) : 10457–60. http://dx.doi.org/10.1021/jp0118470.
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Fernandez, Erwin, Dennis Friedrich, Roel van De Krol et Fatwa Abdi. « Alternate-Target Layer-By-Layer Pulsed Laser Deposition of Epitaxial BiVO4 Thin Films ». ECS Meeting Abstracts MA2022-01, no 36 (7 juillet 2022) : 1559. http://dx.doi.org/10.1149/ma2022-01361559mtgabs.
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Bismuth vanadate (BiVO4) has emerged as one of the highest performing metal oxide photoelectrodes for solar energy-to-fuels applications [1, 2]. This achievement has been largely attributed to the development of high-quality synthesis techniques. Specifically, epitaxial synthetic routes to producing lattice-matched, near single-crystalline quality BiVO4 with minimal extrinsic defects have been essential to understand the fundamental and PEC properties of BiVO4 that are inaccessible by conventional bulk synthesis techniques. In addition, epitaxial synthesis may also be employed as a strategy to further improve the PEC properties of BiVO4 through, for instance, altering the band structure and enhancing the carrier dynamics by strain engineering. Hence, the ability to produce high-quality single-phase epitaxial BiVO4 films is desirable. To date, molecular beam epitaxy (MBE), chemical vapor deposition (CVD), and pulsed laser deposition (PLD) [3] have been used to fabricate epitaxial BiVO4 thin films, with PLD having the advantage of relatively simple experimental setup and material versatility. However, an oft-noted drawback in conventional PLD using single oxide targets is off-stoichiometry in the deposited films; this is especially so for BiVO4 which requires a Bi-rich compound target to achieve a stoichiometric BiVO4 film [4]. This problem is also expected in general for multinary oxides composed of elements with very different ablation properties. To alleviate the limitations of conventional PLD, we employ for the first time alternate-target layer-by-layer PLD as a more elegant approach to produce high quality epitaxial BiVO4 films. Briefly, constituent oxide targets are alternately ablated by an excimer laser (λ= 248 nm) to build the desired film one unit cell thick at a time. Stoichiometry is controlled by the number of shots corresponding to a specified laser fluence for the constituent oxide target. To demonstrate the method, we deposited epitaxial BiVO4 films onto (001)-oriented yttrium-stabilized zirconia (YSZ) using 4N-pure Bi2O3 and V2O5 targets. Films grown are single phase BiVO4 as shown by x-ray diffraction. Out-of-plane diffraction peaks indexed to BiVO4(00l) suggests epitaxy of the film onto the substrate; reciprocal space maps of the asymmetric BiVO4(208) and YSZ(204) peaks further confirm the BiVO4(001) || YSZ(001) epitaxial relationship (top figure). Rocking curves of the BiVO4 (004) peak (FWHM ~ 0.015-0.041) indicate high crystalline perfection of the BiVO4 film, almost approaching that of the YSZ substrate (FWHM ~ 0.010). Thickness dependent-rocking curve studies reveal that BiVO4 films are strained to the substrate for film thicknesses under 22 nm; above this critical thickness, film relaxation ensues. In turn, the resulting optoelectronic properties of the BiVO4 film is dictated by its relaxation state. The optical band gap narrows with film relaxation as observed with spectroscopic ellipsometry. Moreover, steady-state photoluminescence emission spectroscopy reveals a sub-bandgap state (A 2, bottom figure) associated with strained BiVO4 films, on top of a state consistent with band-to-band recombination (B1 ). A higher energy sub-bandgap state (A 1, bottom figure) develops as the film relaxes. The implications of the relaxation state on the charge carrier dynamics and photoelectrochemical properties of BiVO4 will be discussed. Figure: (top) reciprocal space maps of the asymmetric BiVO4(208) and YSZ(204) peaks; (bottom) photoluminescence emission spectra of strained and relaxed BiVO4 films. References: [1] Pihosh, Y., Turkevych, I., Mawatari, K. et al. Photocatalytic generation of hydrogen by core-shell WO3/BiVO4 nanorods with ultimate water splitting efficiency. Sci Rep 5, 11141 (2015) [2] Kim, J., Jang, JW., Jo, Y. et al. Hetero-type dual photoanodes for unbiased solar water splitting with extended light harvesting. Nat Commun 7, 13380 (2016) [3] Zhang, Y., Li, G. Recent Advances of Epitaxial BiVO4 Thin Film: Preparation and Physical and Photoelectrochemical Properties. Braz J Phys 50,185 (2020). [4] Rettie, A. J. E., Mozaffari, S., McDaniel, M. D., Pearson, K. N., Ekerdt, J. G., Markert, J. T., & Mullins, C. B. Pulsed Laser Deposition of Epitaxial and Polycrystalline Bismuth Vanadate Thin Films. J Phys Chem C 118(46), 26543 (2014) Figure 1
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Xu, Gong Qin, Xiao Wei Chen et Xing Yu Mao. « Possible Ferromagnetism in YCuO System ». Solid State Phenomena 298 (octobre 2019) : 181–85. http://dx.doi.org/10.4028/www.scientific.net/ssp.298.181.
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polycrystalline CuxYyOz are made through solid state reaction. Ferromagnetism is found in this YCuO system at room temperature. The ferromagnetism quite probably originates from Cu2Y2O5 , the Copper Yttrium Oxide. The average magnetic moment per Cu2+ is estimated to be 0.04μB. Itinerant electron magnetism is a rational explaination for the observed ferromagnetism. The experiment shows that the excessive amount of Cu may lead more defects and further distortion in the lattice and decrease the exchange interaction. This reminds us that the Copper Yttrium Oxide is a substance not only should be avoided in fabricating YBCO superconductors but also should be considered as a potential substance of magnetic semiconductor.
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Chatterjee, Arindom, Alexandros El Sachat, Ananya Banik, Kanishka Biswas, Alejandro Castro-Alvarez, Clivia M. Sotomayor Torres, José Santiso et Emigdio Chávez-Ángel. « Improved High Temperature Thermoelectric Properties in Misfit Ca3Co4O9 by Thermal Annealing ». Energies 16, no 13 (4 juillet 2023) : 5162. http://dx.doi.org/10.3390/en16135162.
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Ca3Co4O9, a p-type thermoelectric material based on transition-metal oxides, has garnered significant interest due to its potential in thermoelectric applications. Its unique misfit-layered crystal structure contributes to low thermal conductivity and a high Seebeck coefficient, leading to a thermoelectric figure of merit (zT) of ≥1 at 1000 K. Conventionally, it has been believed that thermopower reaches its upper limit above 200 K. However, our thermopower measurements on polycrystalline Ca3Co4O9 samples have revealed an unexpected increase in thermopower above 380 K. In this study, we investigate the effects of high oxygen pressure annealing on Ca3Co4O9 and provide an explanation based on the mixed oxide states of cobalt and carrier hopping. Our results demonstrate that annealing induces modifications in the defect chemistry of Ca3Co4O9, leading to a decrease in electron hopping probability and the emergence of a thermal activation-like behavior in thermopower. These findings carry significant implications for the design and optimization of thermoelectric materials based on misfit cobaltates, opening new avenues for enhanced thermoelectric performance.
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Maier, J., et W. Göpel. « Investigations of the bulk defect chemistry of polycrystalline Tin(IV) oxide ». Journal of Solid State Chemistry 72, no 2 (février 1988) : 293–302. http://dx.doi.org/10.1016/0022-4596(88)90032-1.
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Kosenko, Nadezhda F., et Natalya V. Filatova. « BINDING MATERIALS ACTIVITY REGULATING BY MECHANICAL CHEMICAL METHODS ». IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENIY KHIMIYA KHIMICHESKAYA TEKHNOLOGIYA 61, no 1 (21 décembre 2017) : 66. http://dx.doi.org/10.6060/tcct.20186101.5664.
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It has been established that some abrading treatment of metals oxides crystallizing by halite crystal type (CaO, MgO) reduces their reactive capability. The activity reduction rate was substantially higher than that which could be explained by reducing of oxide specific surface. So, it is reduced for MgO by 30-40 %, while the oxide activity in the magnesium cement – by 250-1000 % (contrary to an impact treatment in a vibration mill). Similar results have been obtained for the interaction between calcium oxide and water, solutions of orthophosphoric acid and salts. CaO powder specific surface before and after abrading treatment by BET method reduces by 50-60 %, while variations of rate constant ranged from 1.5 to 34 times. The same mechanical treatment has a little effect on similar processes in systems where beryllium and zinc oxides are present (structure type of wurtzite). The reactive capability reduction for calcium, magnesium and cadmium oxides can be connected with some changes in the form of polycrystallites' particles in the abrading treatment process. The more prolonged abrading leads to plane sliding and some exposing flat surfaces those are characteristic for crystals of cubic syngony. Thus, an irregular defect layer is removed from grains. Small particles separated in the course of a mechanical treatment from rounded grains at the first stage (up to 5 min) show an increased activity, and then quite dense low active aggregates are formed. The more ordered zones, exposed in the course of an abrading, react slower in comparison to the initial grains, as well as to thin particles being split out. Due to this process the chemical activity reduces. On the contrary, zinc and beryllium oxides crystallites in the abrading treatment practically do not change their outline character; their chemical activity remains constant. Thus, the mechanical abrading treatment of oxides, which crystallize by halite type, really allows reducing their reactive capability in quite wide limits. This opens new opportunities in chemistry of binding materials, allowing achieving needed proportion between rates of chemical interaction and structure-forming in binding systems, which is a necessary condition for a solid monolith compositions' formation.Forcitation:Kosenko N.F., Filatova N.V. Binding materials activity regulating by mechanical chemical methods. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 1. P. 66-71
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Guillén, Cecilia. « Polycrystalline WO3−x Thin Films Obtained by Reactive DC Sputtering at Room Temperature ». Materials 16, no 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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GARCÍA-MÉNDEZ, MANUEL, SANTOS MORALES-RODRÍGUEZ, SADASIVAN SHAJI, BINDU KRISHNAN et PASCUAL BARTOLO-PÉREZ. « STRUCTURAL PROPERTIES OF AlN FILMS WITH OXYGEN CONTENT DEPOSITED BY REACTIVE MAGNETRON SPUTTERING : XRD AND XPS CHARACTERIZATION ». Surface Review and Letters 18, no 01n02 (février 2011) : 23–31. http://dx.doi.org/10.1142/s0218625x1101445x.
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A set of aluminium nitride ( AlN ) and oxidized AlN ( AlNO ) thin films were grown with the technique of direct current (dc) reactive magnetron sputtering. The main purpose of this investigation is to explore the influence of the oxygen on the structural properties of AlN and AlNO films. The crystalline properties and chemical identification of phases were studied by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), respectively. Electrical properties were analyzed from I-V measurements. It was found that films crystallized under the AlN würzite structure and presented a polycrystalline preferential growth along [0001] direction, perpendicular to substrate. Small amounts of secondary aluminium oxide phases were detected too. The oxide phases can induce defects, which can alter crystallinity of films.
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Zaborac, J. A., J. P. Buban, H. O. Moltaji, S. Stemmer et N. D. Browning. « Cation Coordination At Σ Grain Boundaries in TiO2 and SrTiO3, and its Effect on the Local Electronic Properties ». Microscopy and Microanalysis 5, S2 (août 1999) : 792–93. http://dx.doi.org/10.1017/s1431927600017281.
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Grain boundaries have long been known to have a dominant effect on the electronic properties of polycrystalline materials. In the case of electroceramic oxides, the thermodynamics of defect formation (vacancies or interstitials, cations or anions) are usually invoked to predict the presence of a space charge potential at the grain boundaries. The relative energetics for the formation of each type of defect determines the size and sign of this potential barrier and thus, the effect that boundaries have on the overall electronic properties of the materials. However, a limitation to this continuum thermodynamics approach is that it does not consider the effect of the grain boundary structure.To investigate whether the grain boundary atomic structure can have an effect on the energetics of defect formation and hence the electronic properties, here we examine the structure of Σ5 boundaries in two systems, SrTiO3 (perovskite) and TiO2(rutile).
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Lombos, B. A. « Deep levels in semiconductors ». Canadian Journal of Chemistry 63, no 7 (1 juillet 1985) : 1666–71. http://dx.doi.org/10.1139/v85-279.
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The role of deep-lying trapping centers in semi-insulating GaAs, polysilicon and polycrystalline tin oxide transparent electrode has been systematically investigated. It was demonstrated that some of the peculiar transport properties of these semiconductors can be elucidated by deep level compensation. A multilevel model is presented to determine the position of the Fermi level as a function of impurity concentrations. These include, quantitatively, the deep-lying levels which have been introduced by doping in the case of GaAs and by grain boundaries in the case of polycrystalline films. In the latter cases the dangling bonds, associated to lattice defects, are characterized by energy levels which are localized in the energy gap. These dangling bonds can act as electron traps when empty and hole traps when occupied. These are the deep levels.In each of the investigated three cases, this concept permitted the elucidation of some of the transport properties of these semiconductors.
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Chopra, Nitin, Bing Hu et Bruce J. Hinds. « Selective growth and kinetic study of copper oxide nanowires from patterned thin-film multilayer structures ». Journal of Materials Research 22, no 10 (octobre 2007) : 2691–99. http://dx.doi.org/10.1557/jmr.2007.0377.
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Selective growth of CuO nanowires on the etched face of Al2O3/Cu/Al2O3 thin-film multilayer patterns was achieved by ambient oxidation at 400 °C. The nanowires were observed to selectively grow only from the pattern edge with diameter limited by the thickness of Cu thin film. Transmission-electron-microscopy (TEM) characterization confirmed CuO nanowires of a monoclinic CuO growing in the [010] crystallographic direction. Nanowire growth kinetics was studied at 400 °C for different cumulative growth durations with initial growth rates of ∼1 nm/min. A base growth mechanism with kinetics limited by oxygen diffusion through defects of a scaling oxide film is consistent with observed kinetics. The oxygen diffusivity is found to be ∼10−11 cm2/s, consistent with the grain-boundary diffusion of oxygen through polycrystalline copper oxide.
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Walker, John F., J. C. Reiner et C. Solenthaler. « Preparation of TEM samples by focused ion beams ». Proceedings, annual meeting, Electron Microscopy Society of America 53 (13 août 1995) : 518–19. http://dx.doi.org/10.1017/s0424820100138968.
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The high spatial resolution available from TEM can be used with great advantage in the field of microelectronics to identify problems associated with the continually shrinking geometries of integrated circuit technology. In many cases the location of the problem can be the most problematic element of sample preparation. Focused ion beams (FIB) have previously been used to prepare TEM specimens, but not including using the ion beam imaging capabilities to locate a buried feature of interest. Here we describe how a defect has been located using the ability of a FIB to both mill a section and to search for a defect whose precise location is unknown. The defect is known from electrical leakage measurements to be a break in the gate oxide of a field effect transistor. The gate is a square of polycrystalline silicon, approximately 1μm×1μm, on a silicon dioxide barrier which is about 17nm thick. The break in the oxide can occur anywhere within that square and is expected to be less than 100nm in diameter.
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Anderson, Lawrence O., Adrian Xiao Bin Yong, Elif Ertekin et Nicola H. Perry. « Modifying Crystal Symmetry and B-O Charge Distribution to Tailor Chemical Expansion in Mixed Conducting Perovskites ». ECS Meeting Abstracts MA2022-01, no 37 (7 juillet 2022) : 1624. http://dx.doi.org/10.1149/ma2022-01371624mtgabs.
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The exchange of ions between a lattice and the gaseous phase makes mixed conducting oxides ideal for a range of electrochemical applications. Altering oxygen ion concentration is accompanied by a change to electronic species concentrations, and this influences electrical, chemical, kinetic, and mechanical properties. The stability of electrochemical devices like fuel cells and batteries can heavily rely on the mechanical response to changes in chemical defect concentrations. Under both dynamic and steady-state operation of these devices, large volume strains and strain mismatch at interfaces can result in fracture, warping, and delamination that can cause performance degradation and/or failure. Strains between different materials are compared using the coefficient of chemical expansion (CCE), which normalizes the isothermal chemical strain by the change in defect concentration. Here, we advance the understanding of chemo-mechanical coupling through the study of PrGa0.9Mg0.1O3-δ and BaPr0.9Y0.1O3-δ by demonstrating CCEs 2-5x lower than any previously reported perovskite oxide1. Isothermal CCEs were evaluated with in situ, high temperature, and variable atmosphere x-ray diffraction and dilatometry for chemical strains, and with thermogravimetric analysis for stoichiometry changes. The experimental results show chemical strains to be significantly lower than predictions from simple empirical models that assume pseudo-cubic structures and full charge localization on multivalent cations, like Pr. To evaluate actual charge distribution, in situ impedance spectroscopy and density functional theory calculations were performed. The collaboration of experimental and computational work combines accurate and reliable material characterization with insights into atomic and electronic structures that are difficult to probe experimentally. Our results for the studied compositions indicate 2 primary factors that can be used to modify CCEs: 1) Altering the crystal structure away from the isotropic, cubic phase encourages anistropic expansion and lower CCEs in polycrystalline materials, and 2) Varying the distribution of charge along B-O bonds is shown to dramatically alter the CCE. While the first factor provides rather clear guidance to tailor expansion, we elaborate on the second by suggesting band structure design principles for near-zero redox-strain perovskites, and the benefit of locating holes partially or fully on oxygen is highlighted. These new findings add to the growing collection of crystal-chemical design rules for the rational tailoring of chemo-mechanical coupling in perovskite oxides. (1) Anderson, L. O.; Yong, A. X. Bin; Ertekin, E.; Perry, N. H. Toward Zero-Strain Mixed Conductors: Anomalously Low Redox Coefficients of Chemical Expansion in Praseodymium-Oxide Perovskites. Chem. Mater. 2021, 33 (21), 8378–8393. https://doi.org/10.1021/ACS.CHEMMATER.1C02739.
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Xu, Xu, Chaoqi Xiong, Shaoping Mao et Wenjuan Yao. « Established Model on Polycrystalline Graphene Oxide and Analysis of Mechanical Characteristic ». Crystals 12, no 3 (12 mars 2022) : 382. http://dx.doi.org/10.3390/cryst12030382.
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It may cause more novel physical effects that the combination with in-plane defects induced by grain boundaries (GBs) and quasi three-dimensional system induced by oxidation functional group. Different from those in blocks, these new physical effects play a significant role in the mechanical properties and transport behavior. Based on the configuration design, we investigate the in-plane and out-plane geometric deformation caused by the coupling of GBs and oxygen-containing functional groups and establish a mechanical model for the optimal design of the target spatial structure. The results show that the strain rate remarkably affect the tensile properties of polycrystalline graphene oxide (PGO). Under high oxygen content (R = 50%), with the increasing strain rate, the PGO is much closer to ductile fracture, and the ultimate strain and stress will correspondingly grow. The growth of temperature reduces the ultimate stress of PGO, but the ultimate strain remains constant. When the functional groups are distributed at the edge of the GBs, the overall strength decreases the most, followed by the distribution on the GBs. Meanwhile, the strength of PGO reaches the greatest value when the functional groups are distributed away from the GBs.
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Sun, Dehui, Xueliang Kang, Qian Yu, Kun Cui, Xiaoyong Qin, Xuxia Shi, Huaqiang Cai, Tadashi Ohachi, Yuanhua Sang et Hong Liu. « Antisite defect elimination through Mg doping in stoichiometric lithium tantalate powder synthesizedviaa wet-chemical spray-drying method ». Journal of Applied Crystallography 48, no 2 (21 février 2015) : 377–85. http://dx.doi.org/10.1107/s1600576715002113.
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MgO-doped stoichiometric LiTaO3(MgO:SLT) is one of the most promising nonlinear materials. However, its industrial application is limited by the poor optical quality caused by the nonhomogeneous distribution of magnesium. Herein, an MgO:SLT polycrystalline powder was synthesized with a homogenous magnesium distribution by a wet-chemical spray-drying method. A comparative investigation of the coordination state of Ta ions in MgO:SLT powders synthesized by this method and by a conventional solid-state reaction method was performed by X-ray photoelectron spectroscopy. It is proved that the Ta–Li antisite was completely eliminated as a result of the homogeneous Mg doping in the SLT lattice using the wet-chemical spray-drying method. However, for MgO:LT powder produced by the solid-state reaction method, element analysis after acid treatment shows that some Mg ions did not enter the LT lattice after high-temperature calcination. Also, scanning electron microscopy and transmission electron microscopy energy dispersive spectroscopy verified that some MgO particles still exist in the as-synthesized MgO:LT powder. This synthesis method can be used for mass production of high-quality polycrystalline powders for doped crystal growth and some other doped oxide powder products with high melt point.
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Khomenkova, L., V. Kushnirenko, M. Osipenok, K. Avramenko, Y. Polishchuk, I. Markevich, V. Strelchuk, V. Kladko, L. Borkovska et T. Kryshtab. « Effect of Li-doping on Photoluminescence of Screen-printed Zinc Oxide Films ». MRS Proceedings 1766 (2015) : 167–77. http://dx.doi.org/10.1557/opl.2015.424.
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ABSTRACTUndoped and Li-doped ZnO films were fabricated by screen printing approach on sapphire substrate. The effect of Li doping and annealing temperature on the luminescent, optical, electrical and structural properties of the films has been investigated by the photoluminescence (PL), Raman scattering, conductivity, Atomic Force microscopy and X-ray diffraction (XRD) methods. The XRD study revealed that the films have polycrystalline wurtzite structure with grain sizes ranging from 26 to 38 nm. In the undoped ZnO films, the increase of annealing temperature from 800 to 1000 °C resulted in the increase of the grain sizes, film conductivity and the intensity of the ultraviolet PL. The introduction of Li of low concentration of 0.003 wt % at 800 °C or 900 °C allows producing the low-resistive films with enhanced ultraviolet PL and reduced density of crystalline defects. Highly doped films (with 0.3 wt % of Li) were found to be semi-insulating with deteriorated PL properties irrespectively of the annealing temperature. It is shown that introduction of Li in the ZnO films affects their PL spectra mainly via the evolution of the film crystallinity and the density of intrinsic defects.
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Furubayashi, Yutaka, Makoto Maehara et Tetsuya Yamamoto. « Tailoring of Point Defects in Polycrystalline Indium Tin Oxide Films with Postirradiation of Electronegative Oxygen Ions ». ACS Applied Electronic Materials 1, no 8 (17 juillet 2019) : 1545–51. http://dx.doi.org/10.1021/acsaelm.9b00317.
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Gunawan, W., S. Stepanus, L. Lisapaly, F. Mustari et H. S. Sutomo. « Micro crack imaging of silicon solar cells with SEM (Scanning Electron Microscopy) ». IOP Conference Series : Earth and Environmental Science 878, no 1 (1 octobre 2021) : 012062. http://dx.doi.org/10.1088/1755-1315/878/1/012062.
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Abstract Both monocrystalline and polycrystalline silicon based solar cells are proven to be widely used in the photovoltaic industry compared to other solar cell material such as titanium oxide or germanium due to abundant materials and economical production processes, however the problem occurs due to internal (crack) defects in the silicon wafers. The cracks of silicon solar cells occur due to the manufacturing process or when applying them to the field in a relatively short time. Research was also carried out to determine the cause of the cracks and how much damage had occurred that affected the performance of silicon solar cells. By using SEM (Scanning Electron Microscopy) we will prove that, is it clear that the damage caused by production failure of external influences causes defects (micro cracks), holes, burns and so on. The advanced technology owned by SEM is expected to be reliable to find the location of the damage quickly and precisely because the result displayed are very accurate so that it is expected to be an evaluation for the solar cell production process in the future.
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Han, S. D., S. Y. Huang, G. Campet, S. H. Pulcinnelli et C. V. Santilli. « Reversible Electrochemical Insertion of Lithium in Fine Grained Polycrystalline Powders of SnO2 ». Active and Passive Electronic Components 18, no 1 (1995) : 61–68. http://dx.doi.org/10.1155/1995/83138.
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Fine grained SnO2powders have been obtained using an unconventional method. It deals with the well known polymerization method starting from the metallic halide SnCl4with polyethylene oxide (PEO). With this method, SnO2powders, which are free from water and hydroxyl group contaminations and possess small crystallite size (≈50 A∘), are obtained by appropriate pyrolysis of the polymer. Consequently, these powders show good ability to insert reversibly lithium ions in the Li/Li+/LixSnO2cell. Indeed, by minimizing the size of the crystallites, the formation of defect-bonds is favored, particularly at the crystallite surface, acting as reversible (de)grafting sites of Li+. Finally, an easy-to-carry out method to determine the chemical diffusion coefficient of lithium has been proposed.
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Simoen, Eddy, Bogdan Cretu, Wen Fang, Marc Aoulaiche, Jean Marc Routoure, Regis Carin, Jun Luo, Chao Zhao et Cor Claeys. « Low-Frequency Noise Spectroscopy of Bulk and Border Traps in Nanoscale Devices ». Solid State Phenomena 242 (octobre 2015) : 449–58. http://dx.doi.org/10.4028/www.scientific.net/ssp.242.449.
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The principles and application of Generation-Recombination (GR) noise spectroscopy will be outlined and illustrated for the case of traps in Ultra-Thin Buried Oxide Silicon-on-Insulator nMOSFETs and for vertical polycrystalline silicon nMOSFETs. It will be shown that for scaled devices the GR noise is originating from a single defect, giving rise to a so-called Random Telegraph Signal (RTS). Several methods will be described for an accurate extraction of the RTS parameters (amplitude, up and down time constant). It will be demonstrated that besides the deep-level parameters also the position of the trap in the channel can be derived from a numerical modeling of the RTS amplitude.
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Wang, Qi, Zhi Jian Peng, Yang Wang et Xiu Li Fu. « Deposition and Electrical Resistivity of Oxygen-Deficient Tin Oxide Films Prepared by RF Magnetron Sputtering at Different Powers ». Solid State Phenomena 281 (août 2018) : 504–9. http://dx.doi.org/10.4028/www.scientific.net/ssp.281.504.
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A series of oxygen-deficient tin oxide thin films were deposited by radio frequency magnetron sputtering a sintered tin oxide ceramic target under pure argon atmosphere at different sputtering powers (80-160 w) under the based pressure of no more than 2.0×10-4 Pa, sputtering pressure of 2.0 Pa and deposition time of 20 min. It was revealed that all the as-deposited films were oxygen-deficient tin oxide films, and the main defect in films was oxygen vacancy (VO), whose concentration gradually decreased with the increase of sputtering power. The films prepared at a power of no more than 120 w were amorphous, and as the sputtering power increased to 140 and 160 w, the deposited thin films exhibited polycrystalline characteristics with (110), (101) and (211) diffraction peaks of tin oxide. The grain size, deposition rate as well as thickness of the obtained films rose up with increasing sputtering power. In addition, as the sputtering power raised, the electrical resistivity of the films increased, due to the electron conducting mechanism controlled by VO in the samples.
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Furuta, Mamoru, et Yusaku Magari. « (Invited, Digital Presentation) Nondegenerate Hydrogen-Doped Polycrystalline Indium Oxide (InOx:H) Thin Films for High-Mobility Thin Film Transistors ». ECS Meeting Abstracts MA2022-02, no 35 (9 octobre 2022) : 1266. http://dx.doi.org/10.1149/ma2022-02351266mtgabs.
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Transparent metal oxide semiconductors (OSs) have been extensively investigated for use as the active channel layer of thin film transistors (TFTs) for next-generation flat-panel displays, nonvolatile memories, image sensors, and pH sensors, to name a few. Among OSs, the amorphous In–Ga–Zn–O (IGZO) has attracted particular attention for TFT applications owing to its high field effect mobility (μFE) of more than 10 cm2V−1s−1, steep subthreshold swing (S.S.), extremely low off-state current, large-area uniformity, and good bias stress stability. Although the μFE of an IGZO TFT is approximately one order of magnitude higher than that of an amorphous Si TFT, further improvement of the μFE of OS TFTs is required to expand their range of applications as an alternative to polycrystalline Si TFT. Single-crystalline In2O3 has a Hall mobility as high as 160 cm2V−1s−1, which makes amorphous (a-) or polycrystalline (poly-) InOx a potential material for enhancing the μFE of OS TFTs. However, undoped InOx thin films is known as a degenerate semiconductor with high background electron density of over 1020 cm-3, which is attributed to the presence of native defects, such as oxygen vacancies, making them unsuitable for a channel material of OS TFTs. In this presentation, nondegenerate hydrogen-doped polycrystalline InOx (poly-InOx:H) thin films were successfully prepared by low-temperature solid phase crystallization (SPC). A degenerate amorphous InOx:H thin film was deposited by sputtering in Ar, O2, and H2 gases, and an amorphous to polycrystalline phase transition (SPC) of the film was achieved after PDA at more than 175 °C. By PDA at 250 °C in air, a nondegenerate poly-InOx:H film could be obtained with a carrier density as low as 2.4 × 1017 cm−3, which is approximately three orders of magnitude lower than that of the initial a-InOx:H film. The TFTs with a 50 nm thick nondegenerate poly-InOx:H channel could be fully depleted by a gate electric field. A maximum μFE of 125.7 cm2V−1s−1 was exhibited by the TFT with the poly-InOx:H channel. The use of a nondegenerate poly-InOx:H film is a promising approach to boost the μFE of OS TFTs.
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R, Suresh, Thirumal Valavan K, Justin Paul M et Indira Priyadharshini T. « Implication of Mn concentration on the properties of cerium oxide thin films ». NanoNEXT 1, no 1 (30 décembre 2020) : 1–9. http://dx.doi.org/10.34256/nnxt2011.
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Uniform and adhesive Manganese doped cerium oxide (MDC) films are successfully deposited by Nebulizer Spray Pyrolysis (NSP) technique. The MDC films are characterized by XRD, FT-IR, UV-ViS, PL and I-V analysis. X-ray diffraction peaks reveal the single-phase polycrystalline cubic fluorite structure with preferential orientation along (2 0 0) direction. The broad bands observed at 695, 659, 538 and 517 cm-1 are due to the envelope of (Ce=O) symmetric, asymmetric terminal stretching and phonon band of metal oxide (Ce-O) network from FT-IR spectra. The transmittance decreases with Mn concentration due to the increase in scattering of photon by crystal defects created by doping and lower ionic size of Mn. The electrons in the outer orbits have travelled to the higher energy levels and have occupied vacant positions in energy bands. Some of the NBE emission and green emission peaks are vanished at higher doping level of Mn. The occurrence of a strong and broad blue emission peak at 15% for MDC films has been confirmed from emission spectra.
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Nguyen, N. V., Albert V. Davydov, Deane Chandler-Horowitz et Martin M. Frank. « Sub-bandgap defect states in polycrystalline hafnium oxide and their suppression by admixture of silicon ». Applied Physics Letters 87, no 19 (7 novembre 2005) : 192903. http://dx.doi.org/10.1063/1.2126136.
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Lai, Chun‐Yen, Yu‐Ting Lin, Hung‐Kun Hsu, Ding‐Yeong Wang, Wen‐Wei Wu et Ping‐Hung Yeh. « Enhancement in the Detection Ability of Metal Oxide Sensors Using Defect‐Rich Polycrystalline Nanofiber Devices ». Global Challenges 4, no 11 (28 septembre 2020) : 2000041. http://dx.doi.org/10.1002/gch2.202000041.
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Hou, R. Z., P. Ferreira et P. M. Vilarinho. « Observation of Hierarchical Porous BaTiO3 Derived from Hard Template ». Microscopy and Microanalysis 15, S3 (juillet 2009) : 49–50. http://dx.doi.org/10.1017/s1431927609990705.
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AbstractThe morphology control at the mesoscale, via the design of size, shape, surface, interface, porosity and patterning of the meso-components, has gained increasing attention in the recent past and is expected to endue materials with novel functions. Most reports on mesoporous materials are on amorphous silica or simple oxides with amorphous or polycrystalline framework. It is still quite challenging to achieve functional multi-metal-oxides possessing highly porous structure. On the other hand, the synthesis and characterization of nano-sized ferroics has recently become important since it was predicted a dependence, for instance of the ferroelectric response, on the size and morphology. Moreover, the combination of different materials at the nanoscale creating multifunctional nanocomposites, where new properties resulting from scale, interface and defect phenomena are expected, is a new field that requires exploitation. Crystal size, surface area, surface curvature, and charges on the surface singnificantly influence the physical properties of ferroics at the nano-scale. Within our studies of the porous ferroelectrics, we have prepared BaTiO3 crystals with nanoporosity inside with a sol-precipitation process involving polymer or surfactant micelles. In this work, we present the microscopic characterization of porous BaTiO3 derived from hard matrix.
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Heidaryan, Narges, et Hosein Eshghi. « An Investigation on the Effect of the Catalyst on Physical Properties of Silicon Oxide Nanostructures Prepared by CVD Technique ». Advanced Materials Research 829 (novembre 2013) : 173–76. http://dx.doi.org/10.4028/www.scientific.net/amr.829.173.
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Here, nano and microstructures of silicon oxide layers grown on p-Si (111) wafer have synthesized by evaporating SnCl2.2H2O powder in a mixture of Ar and O2 gas flow using chemical vapor deposition (CVD) technique. The growth temperature and the vacuum pressure were 950 °C and 10-3 torr, respectively. Through this study, samples have characterized by SEM, XRD, EDS and PL methods. The grown sample while has a combination of porous and layered morphology, it has a polycrystalline nature including a mixture of SiO2-x (002) and SnO2 phases. The EDS elemental analysis confirmed the presence of Si, O and Sn atoms in the composition, which is consistent with the XRD data. The PL spectrum show a strong peak in violet region (424 nm) attributed to the crystal defects at the SiO2-x and SnO2 interfaces.
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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, no 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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Chaithanatkun, Natpasit, Korakot Onlaor, Thutiyaporn Thiwawong et Benchapol Tunhoo. « Modification of Structural and Vibrational Properties of ZnO Nanoparticles Prepared by Simple Chemical Precipitation Method ». Key Engineering Materials 675-676 (janvier 2016) : 138–41. http://dx.doi.org/10.4028/www.scientific.net/kem.675-676.138.
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In this work, zinc oxide (ZnO) nanoparticles were synthesized by simple chemical precipitation method in the present of zinc nitrate as zinc precursor and sodium hydroxide as hydroxide precursor. The vitamin C was used as modifier media to modify the structural properties of ZnO nanoparticles. The microstructures of ZnO nanoparticles were characterized by field emission scanning electron microscope (FE-SEM) and transmission electron microscope (TEM). Selected area electron diffraction (SAED) patterns showed that polycrystalline hexagonal phase of ZnO. The defects and impurity contents in nanoparticles were investigated by Fourier transform infrared (FT-IR) spectroscopy. The results show few carboxylate and hydroxyl impurities for larger particles when addition modifier increases. Surface areas of nanoparticles were measured by Brunauer Emmett Teller (BET) method. In addition, the results exhibited the dramatically change in structural properties of ZnO nanoparticles due to the effect of vitamin C.
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Čeh, M., H. Gu, H. Müllejans et A. Rečnik. « Analytical electron microscopy of planar faults in SrO-doped CaTiO3 ». Journal of Materials Research 12, no 9 (septembre 1997) : 2438–46. http://dx.doi.org/10.1557/jmr.1997.0322.
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Oxide-rich planar faults within a perovskite matrix are the prevailing type of extended defects in polycrystalline SrO-doped CaTiO3. These defects form, depending on the temperature of sintering, random networks, or ordered structures. The chemistry of the polytypoid, the isolated planar faults, and the perovskite phase have been studied by spatially resolved electron energy-loss and energy-dispersive x-ray spectroscopies using a dedicated scanning transmission electron microscope. We have found that Sr ions from SrO additions preferably substitute Ca in the CaTiO3 lattice, thus forming a solid solution (Ca1–xSrx)TiO3. The surplus of Ca ions forms single and ordered CaO-rich planar faults in the host (Ca1–xSrx)TiO3 phase. Whereas the excess Ca segregates in a form of single planar faults at lower temperatures, it forms a stable polytypoidic phase at higher temperatures. For materials having up to 25 mol% of SrO additions, this phase has (Ca1–xSrx)4Ti3O10 composition, comprising a sequence of CaO faults followed by three (Ca1–xSrx)TiO3 perovskite layers. Analytical electron microscopy revealed that the composition of the single planar faults, formed at lower temperatures, is identical to that of polytypoids, which are stable at higher sintering temperatures.
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Alireza, Heidari. « Effect of Photoconductivity Precursor Volume on Structural, Physical, Electrical and Optical Properties of Thin Layers of Cadmium Oxide (CdO) Nanostructures Produced Using Spray Pyrolysis Technique ». International Journal of Membrane Science and Technology 8, no 2 (9 décembre 2021) : 40–53. http://dx.doi.org/10.15379/2410-1869.2021.08.02.04.
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Thin layers of Cadmium Oxide (CdO) are produced over glassy substrate by spray pyrolysis technique with precursor volumes of 50, 75 and 100 (ml). FESEM images of samples show the formation of nanometric structures and structural characterization of them resulted from XRD spectroscopy indicate the formation of cubic polycrystalline structure in growing layers with preferred direction of (111). Evaluating the optical properties of samples show that optical band gap of layers is reduced from 3.6 to 3.4 (eV) by increasing the precursor volume and the optical absorption coefficient of samples is in UV region at about 105 (cm-1). Data analysis indicates that the produced sample in volume of 100 mL has the smallest penetration depth (smaller than 200 nm) in UV region. On the other hand, thin layers of Cadmium Oxide (CdO) with various volumes of Cadmium acetate solution (40, 50 and 70 ml) were deposited using spray pyrolysis technique over a glassy substrate. Samples were investigated using FESEM images, XRD and UV-Vis spectra as well as I-V characteristic. It was found that all samples were grew up with polycrystalline nanostructures along the preferred direction of (002). In addition, it was found that grew up sample in the volume of 50 (ml) are of optimum photoconductivity condition in visible range regarding optimum structural (largest crystallite size and lowest crystallite defect density) and optical (smallest band gap and highest light absorption) conditions.
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Jiang, J., O. O. Awadelkarim, J. Werking, G. Bersuker et Y. D. Chan. « Fowler–Nordheim stressing of polycrystalline Si oxide Si structures : Observation of stress induced defects in the oxide, oxide/Si interface, and in bulk silicon ». Journal of Vacuum Science & ; Technology A : Vacuum, Surfaces, and Films 15, no 3 (mai 1997) : 875–79. http://dx.doi.org/10.1116/1.580724.
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