Journal articles: 'Defects formation'

1

Zhan, Hai Fei, Yuan Tong Gu, Cheng Yan, and Prasad K. D. V. Yarlagadda. "Numerical Exploration of the Defect’s Effect on Mechanical Properties of Nanowires under Torsion." Advanced Materials Research 335-336 (September 2011): 498–501. http://dx.doi.org/10.4028/www.scientific.net/amr.335-336.498.

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Molecular dynamics (MD) simulations have been carried out to investigate the defect’s effect on the mechanical properties of single-crystal copper nanowire with different surface defects, under torsion deformation. The torsional rigidity is found insensitive to the surface defects and the critical angle appears an obvious decrease due to the surface defects, the largest decrease is found for the nanowire with surface horizon defect. The deformation mechanism appears different degrees of influence due to surface defects. The surface defects play a role of dislocation sources. Comparing with single intrinsic stacking faults formation for the perfect nanowire, much affluent deformation processes have been activated because of surface defects, for instance, we find the twins formation for the nanowire with a surface 45odefect.

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Melikhova, Oksana, Jakub Čížek, Ivan Procházka, Tetyana E. Konstantinova, and Igor A. Yashchishyn. "Inhibition of Positronium Formation in Yttria Stabilized Zirconia Nanopowders Modified by Addition of Chromia." Materials Science Forum 733 (November 2012): 249–53. http://dx.doi.org/10.4028/www.scientific.net/msf.733.249.

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The effect of chromia additive on defects in yttria stabilized zirconia (YSZ) nanopowders was investigated in this work. It was found that positrons are trapped at vacancy-like misfit defect at grain boundaries and at larger defects situated at triple points. Moreover, a long-lived ortho-positronium contribution was found in YSZ nanopowder without chromia. Addition of chromia prolongs the lifetime of positrons trapped at vacancy-like misfit defects which indicates segregation of Cr ions at grain interfaces and interaction of Cr with vacancy-like misfit defets. Moreover addition of chromia completely suppresses formation of positronium.

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Kumar, Deepak, and Manu Khare. "Formation and Control of Defects in Iron Castings." International Journal of Scientific Research 2, no. 5 (June 1, 2012): 245–46. http://dx.doi.org/10.15373/22778179/may2013/81.

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Yoshino, M., Y. Shinzato, and Masahiko Morinaga. "Energetics of Native Defects in Al₂O₃ and SiO₂." Materials Science Forum 449-452 (March 2004): 713–16. http://dx.doi.org/10.4028/www.scientific.net/msf.449-452.713.

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Formation energies of various defects in Al2O3and SiO2are calculated by using the plane-wave pseudopotential method. Also, the formation energies of Schottky defects and Frenkel defects are evaluated on the basis of these calculations. It is shown that formation energies of these defects are higher in SiO2than in Al2O3. In other words, less defects are formed in SiO2than in Al2O3. It is also found that the principal defect is the cation Frenkel defect in Al2O3but the anion Frenkel defect in SiO2. These results agree with the experimental results that Al ions diffuse preferably in Al2O3but oxygen ions diffuse in SiO2at high temperatures.

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Goyal, Anuj, Kiran Mathew, Richard G. Hennig, Aleksandr Chernatynskiy, Christopher R. Stanek, Samuel T. Murphy, David A. Andersson, Simon R. Phillpot, and Blas P. Uberuaga. "The Conundrum of Relaxation Volumes in First-Principles Calculations of Charged Defects in UO2." Applied Sciences 9, no. 24 (December 4, 2019): 5276. http://dx.doi.org/10.3390/app9245276.

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The defect relaxation volumes obtained from density-functional theory (DFT) calculations of charged vacancies and interstitials are much larger than their neutral counterparts, seemingly unphysically large. We focus on UO2 as our primary material of interest, but also consider Si and GaAs to reveal the generality of our results. In this work, we investigate the possible reasons for this and revisit the methods that address the calculation of charged defects in periodic DFT. We probe the dependence of the proposed energy corrections to charged defect formation energies on relaxation volumes and find that corrections such as potential alignment remain ambiguous with regards to its contribution to the charged defect relaxation volume. We also investigate the volume for the net neutral defect reactions comprising individual charged defects, and find that the aggregate formation volumes have reasonable magnitudes. This work highlights the issue that, as is well-known for defect formation energies, the defect formation volumes depend on the choice of reservoir. We show that considering the change in volume of the electron reservoir in the formation reaction of the charged defects, analogous to how volumes of atoms are accounted for in defect formation volumes, can renormalize the formation volumes of charged defects such that they are comparable to neutral defects. This approach enables the description of the elastic properties of isolated charged defects within an overall neutral material.

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Xiao, Zhong Yin, Jian Xiang Wen, Wen Yun Luo, Wen Kai Wu, Ren Xiang Gong, Jian Chong Yin, and Ting Yun Wang. "Formation of Thermally Induced Defects in Silica Optical Material." Advanced Materials Research 853 (December 2013): 62–67. http://dx.doi.org/10.4028/www.scientific.net/amr.853.62.

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Characteristics of silica optical material largely depend on its thermal history. In this paper, formation of thermally induced defects in silica optical material is studied. The formation process of defect is analyzed in detail. The results show that there is an obvious difference in defect formation induced by heating treatment when the composition of silica optical material changes. Defect formation mainly displays as the produce process when the initial defects of the silica material are zero. However, defect formation expresses as the produce and annealing process when the initial defects of the silica material are not zero. The initial defect concentration can be decreased significantly when the silica material is heated in high temperature. At the same time, the new defect is also produced. These theoretic results are consistent with the previous experimental ones.

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CONRAD, EDWARD H. "THE STABILITY OF LOW INDEX METAL SURFACES TO TOPOLOGICAL DEFECTS." International Journal of Modern Physics B 05, no. 03 (February 10, 1991): 427–59. http://dx.doi.org/10.1142/s0217979291000274.

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The study of defect formation at metal surfaces is a fundamental problem in surface physics. An understanding of defect formation is pertinent to growth and diffusion mechanisms. In addition, surface roughening, faceting, and surface melting are all defect mediated phase transitions involving the formation of different topological defects. While the importance of defects at surfaces is well recognized, the study of surface defects has been hampered by the lack of sufficiently accurate experimental techniques. In fact, it is only in the past 6 years that experiments on the thermal generation of defects on metal surfaces have been performed. This review attempts to outline both the theoretical and experimental work on surface defect formation on metal systems.

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Khomichev, V. L. "DEFECTS OF ORE FORMATION ANALYSIS." Geology and mineral resources of Siberia, no. 2 (2021): 92–98. http://dx.doi.org/10.20403/2078-0575-2021-2-92-98.

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The typification of solid mineral deposits is a leading element in the forecast of mineralization. By analogy with magmatic formations, it is based on the ore formation analysis. However, due to the absence of discrete boundaries between formations, their diagnostics encounters insurmountable difficulties, and the classification becomes dubious and controversial. To solve this urgent problem, it is necessary to have a comprehensive discussion in the circle of leading specialists, just as they did when creating the Petrographic Code.

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9

Darmon, Alexandre, Michael Benzaquen, David Seč, Simon Čopar, Olivier Dauchot, and Teresa Lopez-Leon. "Waltzing route toward double-helix formation in cholesteric shells." Proceedings of the National Academy of Sciences 113, no. 34 (August 4, 2016): 9469–74. http://dx.doi.org/10.1073/pnas.1525059113.

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Liquid crystals, when confined to a spherical shell, offer fascinating possibilities for producing artificial mesoscopic atoms, which could then self-assemble into materials structured at a nanoscale, such as photonic crystals or metamaterials. The spherical curvature of the shell imposes topological constraints in the molecular ordering of the liquid crystal, resulting in the formation of defects. Controlling the number of defects, that is, the shell valency, and their positions, is a key success factor for the realization of those materials. Liquid crystals with helical cholesteric order offer a promising, yet unexplored way of controlling the shell defect configuration. In this paper, we study cholesteric shells with monovalent and bivalent defect configurations. By bringing together experiments and numerical simulations, we show that the defects appearing in these two configurations have a complex inner structure, as recently reported for simulated droplets. Bivalent shells possess two highly structured defects, which are composed of a number of smaller defect rings that pile up through the shell. Monovalent shells have a single radial defect, which is composed of two nonsingular defect lines that wind around each other in a double-helix structure. The stability of the bivalent configuration against the monovalent one is controlled by c = h/p, where h is the shell thickness and p the cholesteric helical pitch. By playing with the shell geometry, we can trigger the transition between the two configurations. This transition involves a fascinating waltz dynamics, where the two defects come closer while turning around each other.

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Vachaspati, Tanmay. "Formation of topological defects." Physical Review D 44, no. 12 (December 15, 1991): 3723–29. http://dx.doi.org/10.1103/physrevd.44.3723.

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11

Sobolev, N. A., O. V. Alexandrov, Valentin V. Emtsev, M. I. Makovijchuk, A. V. Merkulov, E. O. Parshin, D. S. Poloskin, and Elena I. Shek. "Influence of Point Defects on Defect Formation in Si:Er." Solid State Phenomena 47-48 (July 1995): 299–306. http://dx.doi.org/10.4028/www.scientific.net/ssp.47-48.299.

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12

Li, Zhan, Yun Liu, Tao Wei, Minghao Li, Ziwen Wang, Zhongying Xue, and Xing Wei. "Investigation on the Transformation of B-Defect in As-Grown Czochralski Silicon Crystal during Annealing Process." ECS Journal of Solid State Science and Technology 11, no. 2 (February 1, 2022): 024007. http://dx.doi.org/10.1149/2162-8777/ac53f6.

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When a silicon ingot is grown by the Czochralski method, different defects, such as A-defect (a dislocation loop or dislocation loops cluster), B-defect (widely accepted as an interstitial atoms cluster), COP (crystal originated particle, a void), and grown-in oxygen precipitates will emerge. Nowadays most crystal defects can be characterized directly. However, due to the extremely small size and stress, B-defects can only be indirectly characterized by the formation of oxygen precipitates. What’s more, it is unclear whether B-defects transform into oxygen precipitates directly or B-defects grow and transform into A-defects firstly and further facilitate oxygen precipitation via the dislocation pinning effect. In this work, after implementing an optimized anneal at 900 °C for 3 h and HCl vapor-phase etch at 900 °C for 2 min, nano-scale defects transformed from B-defects are efficiently detected by a surface particle counter. Scanning electron microscope and energy-dispersive X-ray spectroscopy results prove that these nano-scale defects are all oxygen precipitates. This explicit result indicates that B-defects can induce the formation of oxygen precipitates directly rather than relying on the formation of A-defects, which would help to better understand the characteristic of B-defect in relatively low temperature and the transformation process between different defects in silicon ingot.

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13

Popov, V. D. "Investigation of the Surface Defects in N-Channel MOS Transistors Under Long-Term Low-Dose-Rate Irradiation." Journal of Materials Science Research 6, no. 2 (March 21, 2017): 16. http://dx.doi.org/10.5539/jmsr.v6n2p16.

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Gamma-radiation is commonly used to study surface defects in MOS transistors. Early experiments show two stages of surface-defect formation in a MOS structure under low-intensity gamma irradiation (Popov & Vin, 2014; Popov, 2016). On the first stage the defect formation take place on interface Si-SiO2 from the oxide side. This process is described by an exponential dependence (Rashkeev et al., 2002). In the second stage “additional” surface defects are formed from the Si side. Radiation defects of silicon migrated to interface Si-SiO2 from the semiconductor.The goal of this paper is investigation of surface-defect formation in a MOS transistor using the changing of surface electron mobility.

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Oztunc, Funda, Tevfik Demir, Levent Saltik, and Alper Guzeltas. "Aneurysmal formation in the setting of muscular ventricular septal defects." Cardiology in the Young 17, no. 3 (April 20, 2007): 319–21. http://dx.doi.org/10.1017/s1047951107000418.

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Objective: To emphasize the formation of fibrous aneurysmal structures in the setting of muscular ventricular septal defects Methods: Among patients with muscular ventricular septal defects followed in our institute, we described six who were diagnosed with formation of fibrous aneurysms. Of the patients, one was female and others were male. The age at diagnosis ranged from eight days to 16 years. In one, the defect opened between the ventricular inlets, but in the others the defects occupied the middle part of the apical trabecular septum. Results: The sizes of defects at initial echocardiographic evaluation ranged from 2.9 to 8 millimetres. The period of follow up for four patients was from 5 months to 7 years, one patient could not be followed up, and the other had already been diagnosed when first seen in our Institution. In our second and third patients, no aneurysm was seen during the initial echocardiographic evaluation, and it was recognized during follow-up. In these two patients, sequential echocardiographic examinations showed that the formation of the aneurysm made the defect smaller, with it almost closing in one. Conclusion: Although seen most frequently in the setting of perimembranous defects, fibrous aneurysms can also form adjacent to, and reduce the size of, muscular ventricular septal defects.

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Luo, Jinping, Chenyang Zhou, Qihang Li, and Lijun Liu. "Thermodynamic Formation Properties of Point Defects in Germanium Crystal." Materials 15, no. 11 (June 6, 2022): 4026. http://dx.doi.org/10.3390/ma15114026.

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Point defects are crucial in determining the quality of germanium crystals. A quantitative understanding of the thermodynamic formation properties of the point defects is necessary for the subsequent control of the defect formation during crystal growth. Here, molecular dynamics simulations were employed to investigate the formation energies, total formation free energies and formation entropies of the point defects in a germanium crystal. As far as we know, this is the first time that the total formation free energies of point defects in a germanium crystal have been reported in the literature. We found that the formation energies increased slightly with temperature. The formation free energies decreased significantly with an increase in temperature due to the increase in entropy. The estimated total formation free energies at the melting temperature are ~1.3 eV for self-interstitial and ~0.75 eV for vacancy, corresponding to a formation entropy of ~15 kB for both types of point defects.

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Luo, Jinping, Chenyang Zhou, Qihang Li, and Lijun Liu. "Thermodynamic Formation Properties of Point Defects in Germanium Crystal." Materials 15, no. 11 (June 6, 2022): 4026. http://dx.doi.org/10.3390/ma15114026.

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Point defects are crucial in determining the quality of germanium crystals. A quantitative understanding of the thermodynamic formation properties of the point defects is necessary for the subsequent control of the defect formation during crystal growth. Here, molecular dynamics simulations were employed to investigate the formation energies, total formation free energies and formation entropies of the point defects in a germanium crystal. As far as we know, this is the first time that the total formation free energies of point defects in a germanium crystal have been reported in the literature. We found that the formation energies increased slightly with temperature. The formation free energies decreased significantly with an increase in temperature due to the increase in entropy. The estimated total formation free energies at the melting temperature are ~1.3 eV for self-interstitial and ~0.75 eV for vacancy, corresponding to a formation entropy of ~15 kB for both types of point defects.

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Murat, Altynbek, and Julia E. Medvedeva. "Native point defects in multicomponent transparent conducting oxides." MRS Proceedings 1633 (2014): 37–42. http://dx.doi.org/10.1557/opl.2014.144.

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ABSTRACTThe formation of native point defects in layered multicomponent InAMO4 oxides with A3+=Al or Ga, and M2+=Ca, Mg, or Zn, is investigated using first-principles density functional calculations. We calculated the formation energy of acceptor (cation vacancies, acceptor antisites) and donor (oxygen vacancy, donor antisites) defects within the structurally and chemically distinct layers of InAMO4 oxides. We find that the antisite donor defect, in particular, the A atom substituted on the M atom site (AM) in InAMO4 oxides, have lower formation energies, hence, higher concentrations, as compared to those of the oxygen vacancy which is know to be the major donor defect in binary constituent oxides. The major acceptor (electron “killer”) defects are cation vacancies except for InAlCaO4 where the antisite CaAl is the most abundant acceptor defect. The results of the defect formation analysis help explain the changes in the observed carrier concentrations as a function of chemical composition in InAMO4, and also why the InAlZnO4 samples are unstable under a wide range of growing conditions.

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Hou, Ning, Li Zhou, Shu Tao Huang, and Li Fu Xu. "Finite Element and Experimental Analysis of Edge Defects Formation during Orthogonal Cutting of SiCp/Al Composites." Advanced Materials Research 500 (April 2012): 146–51. http://dx.doi.org/10.4028/www.scientific.net/amr.500.146.

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In this paper, a finite element method was used to dynamically simulate the process of the edge defects formation during orthogonal cutting SiCp/Al composites. The influence of the cutting speed, cutting depth and rake angle of the PCD insert on the size of the edge defects have been investigated by using scanning electron. According to the simulated results, it can be provided that the cutting layer material has an effect on transfer stress and hinder the chip formation in the critical transition stage, and the critical transition point and distance are defined in this stage. The negative shear phenomenon is found when the chip transit to the edge defects in the flexure deformation stage, so the process of the chip formation is the basis of the edge defects formation. In addition, the relationship between the nucleation and propagation direction of the crack and the variation of the edge defect shape on the workpiece was investigated by theory, and it found that the negative shear angle formation is the primary cause of the edge defect formation. A mixed mode crack is found in the crack propagation stage. The sizes of edge defects were measured by the experiment and simulation, and the edge defect size decrease with the increasing of tool rake angle, while increase with increasing cutting depth and cutting speed.

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Yilmaz, Ayca, Dilek Helvacioglu-Yigit, Cansu Gur, Handan Ersev, Gullu Kiziltas Sendur, Egemen Avcu, Canan Baydemir, and Paul Vincent Abbott. "Evaluation of Dentin Defect Formation during Retreatment with Hand and Rotary Instruments: A Micro-CT Study." Scanning 2017 (2017): 1–7. http://dx.doi.org/10.1155/2017/4868603.

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The purpose of this study was to compare the incidence and longitudinal propagation of dentin defects after gutta-percha removal with hand and rotary instruments using microcomputed tomography. Twenty mandibular incisors were prepared using the balanced-force technique and scanned in a 19.9 μm resolution. Following filling with the lateral compaction technique, gutta-percha was removed with ProTaper Universal Retreatment (PTUR) or hand instruments. After rescanning, a total of 24,120 cross-sectional images were analyzed. The numbers, types, and longitudinal length changes of defects were recorded. Defects were observed in 36.90% of the cross sections. A total of 73 defects were comprised of 87.67% craze lines, 2.73% partial cracks, and 9.58% fractures. No significant difference in terms of new defect formation was detected between the retreatment groups. The apical and middle portions of the roots had more dentin defects than the coronal portions. Defects in three roots of the PTUR instrument group increased in length. Under the conditions of this in vitro study, gutta-percha removal seemed to not increase the incidence of dentin defect formation, but the longitudinal defect propagation finding suggests possible cumulative dentinal damage due to additional endodontic procedures. Hand and rotary instrumentation techniques caused similar dentin defect formation during root canal retreatment.

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KUMAR, V. SUNIL, BISWANATH LAYEK, AJIT M. SRIVASTAVA, SOMA SANYAL, and VIVEK K. TIWARI. "SKYRMION FORMATION IN 1+1 DIMENSIONS WITH CHEMICAL POTENTIAL." International Journal of Modern Physics A 21, no. 06 (March 10, 2006): 1199–219. http://dx.doi.org/10.1142/s0217751x06029508.

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Formation of topological objects during phase transitions has been discussed extensively in literature. In all these discussions, defects and antidefects form with equal probabilities. In contrast, many physical situations, such as formation of baryons in relativistic heavy-ion collisions at present energies, flux tube formation in superconductors in the presence of external magnetic field, and formation of superfluid vortices in a rotating vessel, require a mechanism which can bias (say) defects over antidefects. Such a bias can crucially affect defect–antidefect correlations, apart from its effects on defect density. In this paper we initiate an investigation for the basic mechanism of biased formation of defects. For Skyrmions in 1+1 dimensions, we show that incorporation of a chemical potential term in the effective potential leads to a domain structure where order parameter is spatially varying. We show that this leads to biased formation of Skyrmions.

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HONEY, SHEHLA, JAMIL ASIM, ISHAQ AHMAD, TINGKAI ZHAO, MAAZA MALEK, and SHAHZAD NASEEM. "STUDY OF FORMATION OF DEFECTS/DEFECT CLUSTERS IN NICKEL NANOWIRES." Surface Review and Letters 27, no. 10 (July 6, 2020): 1950216. http://dx.doi.org/10.1142/s0218625x19502160.

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In this paper, formation of defects/defect clusters in nickel nanowires (Ni-NWs) due to interaction of a 60 kilo-electron-volt (keV) beam of proton (H[Formula: see text] ions is studied. Ni-NWs are exposed to various fluencies of H[Formula: see text] ions ranging between [Formula: see text] and [Formula: see text][Formula: see text]ions/cm2. The analysis of pristine and H[Formula: see text] ion-irradiated Ni-NWs samples is mainly done using transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques. Stopping range of ions in matter (SRIM) simulation software is employed to verify the production of defect clusters in Ni-NWs theoretically. Furthermore, insight of creation of defects in Ni-NWs due to interaction of low energy H[Formula: see text] ions in keV range is made using the theory of collision cascade effect. The study of defect clusters induced in Ni-NWs under H[Formula: see text] ions beam irradiation is essential for application of Ni-NW-based nanodevices in harsh environment containing plenty of H[Formula: see text] ions such as for use in spacecraft equipped for space missions.

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Tan, T. Y., and U. G�sele. "Point defects, diffusion processes, and swirl defect formation in silicon." Applied Physics A Solids and Surfaces 37, no. 1 (May 1985): 1–17. http://dx.doi.org/10.1007/bf00617863.

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Polák, Jaroslav, and Jiří Man. "Cyclic Slip Localization and Crack Initiation in Crystalline Materials." Advanced Materials Research 891-892 (March 2014): 452–57. http://dx.doi.org/10.4028/www.scientific.net/amr.891-892.452.

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Cyclic plastic straining in crystalline materials is localized to persistent slip bands (PSBs) and results in formation of persistent slip markings (PSMs) consisting of extrusions and intrusions. Intensive plastic strain in PSBs results in dislocation interactions and formation of point defects. The extended model based on point defect formation, migration and annihilation is presented describing surface relief formation in the form of extrusion-intrusion pairs. Point defect migration and resulting mass transfer is the principle source of cyclic slip irreversibility leading to crack-like defects - intrusions. Fatigue cracks start in the tip of sharp intrusions.

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Jäger, Wolfgang. "Diffusion and Defect Phenomena in III-V Semiconductors and their Investigation by Transmission Electron Microscopy." Diffusion Foundations 17 (July 2018): 29–68. http://dx.doi.org/10.4028/www.scientific.net/df.17.29.

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This article reviews the studies of diffusion and defect phenomena induced by high-concentration zinc diffusion in the single-crystal III-V compound semiconductors GaAs, GaP, GaSb and InP by methods of transmission electron microscopy and their consequences for numerical modelling of Zn (and Cd) diffusion concentration profiles. Zinc diffusion from the vapour phase into single-crystal wafers has been chosen as a model case for interstitial-substitutional dopant diffusion in these studies. The characteristics of the formation of diffusion-induced extended defects and of the temporal evolution of the defect microstructure correlate with the experimentally determined Zn profiles whose shapes depend on the chosen diffusion conditions. General phenomena observed for all semiconductors are the formation of dislocation loops, precipitates, voids, and dislocations and of Zn-rich precipitates in the diffusion regions. The formation of extended defects near the diffusion front can be explained as result of point defect supersaturations generated by interstitial-substitutional zinc exchange via the kick-out mechanism. The defects may act as sinks for dopants and as sources and sinks for point defects during the continuing diffusion process, thereby providing a path to establishing defect-mediated local point defect equilibria. The investigations established a consistent picture of the formation and temporal evolution of defects and the mechanisms of zinc diffusion in these semiconductors for diffusion conditions leading to high-concentration Zn concentrations. Based on these results, numerical modelling of anomalously shaped dopant concentration profiles leads to satisfactory quantitative results and yields information on type and charge states of the point defect species involved, also for near-surface Zn concentration profiles and the absence of extended defects.

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Meng, Weidong, Yanjun Liu, Zhehui Zhu, Shenghang Liu, Yong Shen, and Shizhang Liu. "Injectable Hyaluronic Acid/Human Umbilical Cord Mesenchymal Stem Cells/Bone Morphogenetic Protein-2 Promotes the Repair of Radial Bone Defects in Rabbits." Journal of Biomaterials and Tissue Engineering 12, no. 7 (July 1, 2022): 1378–84. http://dx.doi.org/10.1166/jbt.2022.3051.

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Background: Bone defects are common in orthopedics and can be caused by congenital diseases, trauma, infection, tumors and other reasons. The treatment of large-scale bone defects is a clinical problem faced by orthopedists. The development of tissue engineering technology is expected to solve this problem. Objective: To explore the effect of injectable hyaluronic acid/hUCMSC/BMP-2 on the healing of rabbit radial bone defects. Methods: X-ray examination and tissue specimens were examined to macroscopically observe bone defect healing; tetracycline fluorescence and vonKossa staining were performed to observe the formation of new bone, and H&E staining was performed to examine cartilage and trabecular bone formation. Results: The injectable hyaluronic acid/hUCMSC/BMP-2 could significantly promote the early repair of bone defects and accelerate the process of bone formation. Conclusion: The direct injection of hyaluronic acid/hUCMSC/BMP-2 into afresh bone defect site has a significant beneficial effect on early repair of the bone defect.

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Khirunenko, Lyudmila I., Yu V. Pomozov, Mikhail G. Sosnin, Nikolay V. Abrosimov, M. Höhne, and W. Schröder. "Radiation Defects Formation in Si." Solid State Phenomena 69-70 (August 1999): 209–14. http://dx.doi.org/10.4028/www.scientific.net/ssp.69-70.209.

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27

Khomichev, V. L., and N. E. Egorova. "DEFECTS OF MAGMA FORMATION ANALYSIS." Geology and mineral resources of Siberia, no. 1 (2021): 3–17. http://dx.doi.org/10.20403/2078-0575-2021-1-3-17.

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The formation analysis of igneous rocks is a great achievement of the Soviet science in terms of classifying natural communities of magmatic rocks for the purpose of forecasting and prospecting of associated deposits. But due to the complexity of the problem itself, the uncertainty of boundaries between formational types in the practice of geological works, there are numerous defects that were clearly observed during the regional and interregional correlation of magmatic complexes of the Altai-Sayan region and Yenisey Ridge. The reasons and consequences of these defects, ways of their correction are analyzed.

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Matsuda, Tomohiro. "Formation of cosmological brane defects." Journal of High Energy Physics 2004, no. 11 (November 16, 2004): 039. http://dx.doi.org/10.1088/1126-6708/2004/11/039.

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Araújo, M. G., T. Berglundh, T. Albrekstsson, and J. Lindhe. "Bone formation in furcation defects." Journal of Clinical Periodontology 26, no. 10 (October 1999): 643–52. http://dx.doi.org/10.1034/j.1600-051x.1999.261003.x.

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30

Hsieh, Y. F., and B. Y. Tsui. "Design rule related defects formation." Microelectronics Reliability 38, no. 12 (December 1998): 1871–80. http://dx.doi.org/10.1016/s0026-2714(98)00067-5.

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BRANDENBERGER, ROBERT H. "TOPOLOGICAL DEFECTS AND STRUCTURE FORMATION." International Journal of Modern Physics A 09, no. 13 (May 20, 1994): 2117–89. http://dx.doi.org/10.1142/s0217751x9400090x.

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Topological defects are produced during phase transitions in the very early Universe. They arise in most unified theories of strong, weak and electromagnetic interactions. This article focuses on the role of topological defects in cosmology, with particular emphasis on the models of structure formation based on defects. The role of topological defects in baryogenesis is also reviewed.

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Vdovin, V. I., N. A. Sobolev, D. V. Denisov, and Elena I. Shek. "Defect Formation in MBE Er-Doped Si Light-Emitting Structures." Solid State Phenomena 108-109 (December 2005): 779–86. http://dx.doi.org/10.4028/www.scientific.net/ssp.108-109.779.

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Structural defects in Si:Er layers grown by molecular beam epitaxy have been studied by transmission electron microscopy. Two kinds of second phase precipitates are the main defects in the layers with Er concentration ≥ 2х1019 cm-3: ball-shaped precipitates (4-25 nm) of metallic Er localized at the layer-substrate interface and platelet precipitates of ErSi2 extending through the whole layer. We studied the effect of Er concentration (8х1018 - 4х1019 cm-3) and growth temperature (400 - 700°C) on the defect generation. The peculiarities of defect generation in MBE Si:Er layers implanted with B+ ions were also studied.

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Das, Debtanay, Swarup Bag, Sukhomay Pal, and Abhay Sharma. "Material Defects in Friction Stir Welding through Thermo–Mechanical Simulation: Dissimilar Materials with Tool Wear Consideration." Materials 16, no. 1 (December 28, 2022): 301. http://dx.doi.org/10.3390/ma16010301.

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Despite the remarkable capabilities of friction stir welding (FSW) in joining dissimilar materials, the numerical simulation of FSW is predominantly limited to the joining of similar materials. The material mixing and defects’ prediction in FSW of dissimilar materials through numerical simulation have not been thoroughly studied. The role of progressive tool wear is another aspect of practical importance that has not received due consideration in numerical simulation. As such, we contribute to the body of knowledge with a numerical study of FSW of dissimilar materials in the context of defect prediction and tool wear. We numerically simulated material mixing and defects (surface and subsurface tunnel, exit hole, and flash formation) using a coupled Eulerian–Lagrangian approach. The model predictions are validated with the experimental results on FSW of the candidate pair AA6061 and AZ31B. The influence of tool wear on tool dimensions is experimentally investigated for several sets of tool rotations and traverse speeds and incorporated in the numerical simulation to predict the weld defects. The developed model successfully predicted subsurface tunnel defects, surface tunnels, excessive flash formations, and exit holes with a maximum deviation of 1.2 mm. The simulation revealed the substantial impact of the plate position, on either the advancing or retreating side, on the defect formation; for instance, when AZ31B was placed on the AS, the surface tunnel reached about 50% of the workpiece thickness. The numerical model successfully captured defect formation due to the wear-induced changes in tool dimensions, e.g., the pin length decreased up to 30% after welding at higher tool rotations and traverse speeds, leading to surface tunnel defects.

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Jung, Martin, Steffen Breusch, Wolfgang Daecke, and Tobias Gotterbarm. "The effect of defect localization on spontaneous repair of osteochondral defects in a Göttingen minipig model: a retrospective analysis of the medial patellar groove versus the medial femoral condyle." Laboratory Animals 43, no. 2 (April 2009): 191–97. http://dx.doi.org/10.1258/la.2008.007149.

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Various animal models for experimental osteochondral defect healing have been used in orthopaedic research. Two main defect locations were chosen: the patellar groove or the central part of the medial femoral condyles (MFC). To date, it is not clear whether both locations display similar patterns in critical size osteochondral defect healing. We retrospectively analysed both locations in our minipig model hypothesizing that they show similar healing pattern. Thirty-five defects were analysed after three or 12 months. Osteochondral defects were 10 mm deep and 6.3 mm (MFC, n = 19) in diameter or 8 mm and 5.4 mm, respectively (trochlear groove [TG], n = 16). Semi-quantitative histological scoring and histomorphological evaluation were carried out. Both defect locations showed fillings of fibrous and fibrocartilage-like repair tissue. The osseous defect was closed by endochondral bone formation in the MFC. Semi-quantitative scoring did not show differences, whereas qualitative histomorphological analysis more frequently showed cartilaginous repair tissue in MFC defects. There was more frequent subchondral bone cyst formation in MFC location ( P = 0.05), TG defects resulted in lower postoperative pain. Both defect localizations are suitable for studies on osteochondral healing. Since regenerating with less hyaline-like repair tissue and less subchondral cyst formation, TG is more favourable for experimental osteochondral defect healing in this model.

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Kirste, Lutz, Karolina Grabianska, Robert Kucharski, Tomasz Sochacki, Boleslaw Lucznik, and Michal Bockowski. "Structural Analysis of Low Defect Ammonothermally Grown GaN Wafers by Borrmann Effect X-ray Topography." Materials 14, no. 19 (September 22, 2021): 5472. http://dx.doi.org/10.3390/ma14195472.

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X-ray topography defect analysis of entire 1.8-inch GaN substrates, using the Borrmann effect, is presented in this paper. The GaN wafers were grown by the ammonothermal method. Borrmann effect topography of anomalous transmission could be applied due to the low defect density of the substrates. It was possible to trace the process and growth history of the GaN crystals in detail from their defect pattern imaged. Microscopic defects such as threading dislocations, but also macroscopic defects, for example dislocation clusters due to preparation insufficiency, traces of facet formation, growth bands, dislocation walls and dislocation bundles, were detected. Influences of seed crystal preparation and process parameters of crystal growth on the formation of the defects are discussed.

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Hagimoto, Yoshiya, Hayato Iwamoto, Yosuke Kawabuchi, and Teruomi Minami. "Influence of Ammonia Gas Ambient in IPA Drying Process of the Single Wafer Cleaning System." Solid State Phenomena 195 (December 2012): 231–34. http://dx.doi.org/10.4028/www.scientific.net/ssp.195.231.

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High-performance drying techniques using IPA (isopropyl alcohol) are widely used in the silicon wafer cleaning process. IPA-based drying techniques help prevent the formation of watermarks because they effectively displace any water remaining on a wafer surface. They are thus frequently used in the single wafer cleaning system for advanced devices in which ultra-clean process performance is required. However, as devices are becoming physically smaller, the formation of extremely small defects during cleaning has become a serious problem. It is therefore important to elucidate the mechanism of the defect formation and to take measures to prevent it for future device technologies in which small-size defects can be killer defects during production. In this paper, we performed experiments focused on the process chamber atmosphere in IPA drying of the single wafer cleaning system and describe the mechanism of the defect formation.

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Havlucu, Uğur, Nilüfer Bölükbaşı, Sinem Yeniyol, Şule Çetin, and Tayfun Özdemir. "Effects of Light-Emitting Diode Photobiomodulation Therapy and BioOss as Single and Combined Treatment in an Experimental Model of Bone Defect Healing in Rats." Journal of Oral Implantology 41, no. 4 (August 1, 2015): e110-e117. http://dx.doi.org/10.1563/aaid-joi-d-13-00310.

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The present study assesses histopathologically and histomorphometrically the effects of light-emitting diode (LED) photobiomodulation therapy (LPT) on bone healing in BioOss-filled femoral defects of rats. It has been reported that LPT modulates cellular metabolic processes, leading to an enhanced regenerative potential for biological tissues. Thirty-six male Wistar rats with femoral bone defects were divided into 4 groups: defect group (empty bone defect, without application of LPT), graft group (bone defect filled with BioOss, without application of LPT), (defect+LPT) group (empty bone defect, with application of LPT), and (graft+LPT) group (bone defect filled with BioOss, with application of LPT). An OsseoPulse LED device (wavelength: 618 nm; output power: 20 mW/cm2) was initiated 24 hours postsurgery and performed every 24 hours for 7, 14, and 21 days. The LPT-applied and BioOss-filled defects presented a higher amount of new bone formation with trabeculae formation. These defects showed statistically significant lower values of inflammation severity, and fewer remnants of biomaterial were present. Within the limitations of this study, LPT has positive effects on bone healing histopathologically and histomorphometrically for the defects filled with BioOss 3 weeks after the rats' femora injury.

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Shrivastava, Amitesh, Peter G. Muzykov, B. Pearman, S. Michael Angel, and Tangali S. Sudarshan. "Investigation of Triangular Defects in 4H-SiC 4° Off Cut (0001) Si Face Epilayers Grown by CVD." Materials Science Forum 600-603 (September 2008): 139–42. http://dx.doi.org/10.4028/www.scientific.net/msf.600-603.139.

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Triangular defects and inverted pyramid type defects formed during homoepitaxial growth on 4H-SiC Si face, 4° off-cut towards [11-20] direction have been investigated. Growth parameters responsible for triangular defect formation were identified and optimized for its reduction in this study. It was found that although the high temperature reduces the density of inverted pyramid type defects, it is not the only remedy for reducing their density and cleanliness of susceptor along with the initial growth condition plays a major role in the formation of these defects.

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Huang, Dan, and Yuanming Pan. "First-principles calculations of intrinsic defects in the p-type semiconductor CuAlO2." Canadian Journal of Physics 88, no. 12 (December 2010): 927–32. http://dx.doi.org/10.1139/p10-095.

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Intrinsic defects, including vacancies at the Cu and Al sites (VCu and VAl), substitutional Cu at the Al site (CuAl), and interstitial O (Oi), have been proposed to be responsible for the p-type conductivity in CuAlO2. We have investigated the formation energies of these and other intrinsic defects in CuAlO2 using GGA+U calculations. Our results support previous studies that the potential alignment and image charge correction are required in the calculation of defect formation energies by using the supercell approach. In CuAlO2, these p-type defects (VCu, VAl, CuAl, and Oi) invariably have lower formation energies than their n-type counterparts. Particularly, VCu and CuAl have the lowest formation energies among intrinsic defects, and therefore are most likely responsible for the p-type conductivity. However, the transition levels of the VCu and CuAl defects are deep, which are responsible for the poor p-type conductivity in CuAlO2.

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Kawakita, Shirou, Mitsuru Imaizumi, Shogo Ishizuka, Hajime Shibata, Shigeru Niki, Shuichi Okuda, and Hiroaki Kusawake. "Characterization of Electron-Induced Defects in Cu (In, Ga) Se2 Thin Films by Photoluminescence." MRS Proceedings 1771 (2015): 157–61. http://dx.doi.org/10.1557/opl.2015.405.

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ABSTRACTCIGS thin films were irradiated with 100 or 250 keV electrons to reveal the radiation defect by analyzing PL measurement. The PL intensity decreased due to non-radiative recombination defects induced by electron irradiation. Furthermore, the intensity 0.8 eV peak of the PL spectrum was observed from CIGS films irradiated with 250 eV electrons and is said to correspond to In-antisite defects in CIGS materials. The defects can usually change into InCu-VCu complex defects combined with VCu, since the formation energy of the complex defect is lower than that of each defect. Cu interstitial defects induced by 250 keV electron irradiation would diffuse to VCu of the complex defect, whereupon the complex defect might become an In-antisite defect due to 250 keV electron irradiation.

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Prabhakar, Arun, Michail Papanikolaou, Konstantinos Salonitis, and Mark Jolly. "Minimising Defect Formation in Sand Casting of Sheet Lead: A DoE Approach." Metals 10, no. 2 (February 13, 2020): 252. http://dx.doi.org/10.3390/met10020252.

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Sand casting of lead sheet is a traditional manufacturing process used up to the present due to the special features of sand cast sheet such as their attractive sheen. Similarly to any casting process, sand casting of lead sheet suffers from the presence of surface defects. In this study, a surface defect type, hereby referred to as ‘grooves’, has been investigated. The focus has been laid on the identification of the main factors affecting defect formation in this process. Based on a set of screening experiments performed using Scanning Electron Microscopy (SEM) as well as the existing literature, a number of factors affecting the formation of such defects was identified and their corresponding significance was estimated using the Analysis of Variance (ANOVA) technique. The obtained results suggest that the most significant factor affecting defect formation in sand casting of lead sheet is the composition of the moulding mixture. Defect formation was also proven to be dependent on the sand grain fineness, the quality of the melt and some of the interactions between the aforementioned process parameters. Finally, an optimal set of process parameters leading to the minimisation of surface defects was identified.

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42

Wu, Yifeng, Kelsey J. Mirrielees, and Douglas L. Irving. "On native point defects in ZnSe." Applied Physics Letters 120, no. 23 (June 6, 2022): 232102. http://dx.doi.org/10.1063/5.0092736.

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Aiming at a fundamental understanding of the defect chemistry of pure ZnSe for optical and quantum applications, systematic density functional theory calculations with hybrid exchange-correlation functionals were performed to build an accurate database of native defects in ZnSe, including isolated defects and first nearest-neighbor defect–defect complexes. From the defect formation energies, zinc vacancy is found to be the most prevalent defect as the Fermi level approaches the conduction band edge, while zinc interstitial in the selenium tetrahedron and selenium vacancy become the most prevalent defects as the Fermi level approaches the valence band maximum. The divacancy complex, consisting of first nearest-neighboring zinc and selenium vacancies, is also found to have a favorable binding energy across the entire bandgap. Its formation energy is, however, always higher than either the isolated zinc or selenium vacancy, meaning it will never be the predominant defect in equilibrium. Finally, a point defect with extended spin coherence in Fluorine-implanted ZnSe was recently discovered, and it was found to exhibit a broad emission peak centered at 2.28 eV. The identity of this defect was determined to be either zinc vacancy or its associated complex according to the electron paramagnetic resonance measurements. Explicit simulations of the optical signatures of all zinc vacancy-related native defects were conducted here, showing that both zinc vacancy and divacancy are the most likely native defect contributors to that peak.

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Hossain, Faruque M., Graeme E. Murch, L. Sheppard, and Janusz Nowotny. "The Effect of Defect Disorder on the Electronic Structure of Rutile TiO_2-x." Defect and Diffusion Forum 251-252 (March 2006): 1–12. http://dx.doi.org/10.4028/www.scientific.net/ddf.251-252.1.

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The purpose of this work is to study the effect of bulk point defects on the electronic structure of rutile TiO2. The paper is focused on the effect of oxygen nonstoichiometry in the form of oxygen vacancies, Ti interstitials and Ti vacancies and related defect disorder on the band gap width and on the local energy levels inside the band gap. Ab initio density functional theory is used to calculate the formation energies of such intrinsic defects and to detect the positions of these defect induced energy levels in order to visualize the tendency of forming local mid-gap bands. Apart from the formation energy of the Ti vacancies (where experimental data do not exist) our calculated results of the defect formation energies are in fair agreement with the experimental results and the defect energy levels consistently support the experimental observations. The calculated results indicate that the exact position of defect energy levels depends on the estimated band gap and also the charge state of the point defects of TiO2.

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Ovsiannikova, L. I., G. V. Lashkarev, V. V. Kartuzov, D. V. Myroniuk, M. V. Dranchuk, and A. I. Ievtushenko. "The study of the behavior of Al impurity in ZnO lattice by a fullerene like model." Physics and Chemistry of Solid State 22, no. 2 (April 20, 2021): 204–8. http://dx.doi.org/10.15330/pcss.22.2.204-208.

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The fullerene like Zn32Al4O36 clusters were investigated and the oxygen interstitial Oi acceptor intrinsic defect formation energy as well as Al ionization energy were calculated. The effect of lattice packing defects on the electroactivity of Al impurity was investigated. Analysis of the defects formation energies shows the smaller formation energy of interstitial Oi in a comparison with a formation of Zn vacancy. This allows us to formulate recommendations of technological conditions for films deposition, with improved electroactivity of Al donor.

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45

Ma, Jun, Ying Xu, Jun Tang, and Chunni Wang. "Defects formation and wave emitting from defects in excitable media." Communications in Nonlinear Science and Numerical Simulation 34 (May 2016): 55–65. http://dx.doi.org/10.1016/j.cnsns.2015.10.013.

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Ishikawa, Yukari, Koji Sato, Yoshihiro Okamoto, Noritaka Hayashi, Yong Zhao Yao, and Yoshihiro Sugawara. "Dislocation Formation in Epitaxial Film by Propagation of Shallow Dislocations on 4H-SiC Substrate." Materials Science Forum 717-720 (May 2012): 383–86. http://dx.doi.org/10.4028/www.scientific.net/msf.717-720.383.

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Shallow defects, which were induced by mechanical treatment, on 4H-SiC wafers were investigated. The density and the distribution in depth of shallow defects on the wafers were depended on wafer venders. Most of serious defects such as dislocation array (DA), triangular stacking fault (TRSF) and triangular defect (TRD) in epitaxial film were demonstrated to be caused by shallow dislocations on the surface of the wafers. Revised mechanical polish can reduce the densities of DA, TRSF and TRD in epitaxial film.

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Lebedev, Alexander A., Klavdya S. Davydovskaya, Vitalii V. Kozlovski, Oleg Korolkov, Natalja Sleptsuk, and Jana Toompuu. "Dependence of the Carrier Removal Rate in 4H-SiC PN Structures on the Irradiation Temperature." Materials Science Forum 963 (July 2019): 730–33. http://dx.doi.org/10.4028/www.scientific.net/msf.963.730.

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The influence of 15 MeV proton irradiation temperatures (room temperature (RT) - 700 ° C) on the processes of defect formation in commercially available 4H-SiC JBS structures has been studied. It has been shown that the carrier removal rate does not depend on the irradiation temperature. At the same time, the irradiation temperature affected on the spectrum of introduced radiation defects. The conclusion about the possible influence of SiC crystal lattice structural defects on the processes of radiation defect formation has been made.

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Tiller, W. A., M. Friedman, R. Shaw, N. Cuendet, and T. Halicioglu. "Grown-in point defects and microscopic defect formation in CZ silicon." Journal of Crystal Growth 186, no. 1-2 (March 1998): 113–27. http://dx.doi.org/10.1016/s0022-0248(97)00467-3.

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GONZÁLEZ-VIÑAS, W., S. CASADO, J. BURGUETE, H. MANCINI, and S. BOCCALETTI. "DEFECT DYNAMICS DURING A QUENCH IN A BÉNARD–MARANGONI CONVECTION SYSTEM." International Journal of Bifurcation and Chaos 11, no. 11 (November 2001): 2887–94. http://dx.doi.org/10.1142/s0218127401003930.

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We report experimental evidence of defect formation and dynamics in a symmetry breaking transition for a conduction–convection Bénard–Marangoni system. As opposite to the behavior of perfect patterns, defects appear to interact in a spatial region, responsible for the formation of bounded states that survive much longer than the characteristic time scales. The analysis of the transient defect dynamics allows to define this defect interaction region in the space, giving rise to penta–hepta-like defects on top of the hexagonal pattern. Other defect configurations are shown to disappear rapidly either through dislocations moving toward the boundaries or through dislocation–dislocation annihilation. This evidence suggests that the scaling law of defects in the final structure versus quench time might be investigated by analyzing the probability of two or more dislocations to appear in the same interaction region.

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Oba, Fumiyasu, Hirohiko Adachi, and Isao Tanaka. "Energetics and electronic structure of point defects associated with oxygen excess at a tilt boundary of ZnO." Journal of Materials Research 15, no. 10 (October 2000): 2167–75. http://dx.doi.org/10.1557/jmr.2000.0312.

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The formation energies and electronic structure of zinc vacancies and oxygen interstitials at a tilt boundary of ZnO were investigated by a combination of static lattice and first-principles molecular orbital methods. For both of the defect species, the formation energies were lower than those of the bulk defects at certain sites in the grain boundary. The defects with low formation energies formed electronic states close to the top of the valence band. The interfacial electronic states observed experimentally in ZnO varistors cannot be explained solely by the point defects associated with the oxygen excess: the effects of impurities should be significant for the states.

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Journal articles on the topic 'Defects formation'

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