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Letteratura scientifica selezionata sul tema "Defect recombination"

Autore: Grafiati

Pubblicato: 21 dicembre 2024

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Articoli di riviste sul tema "Defect recombination"

Saeed, Faisal, Muhammad Haseeb Khan, Haider Ali Tauqeer, Asfand Haroon, Asad Idrees, Syed Mzhar Shehrazi, Lukas Prokop, Vojtech Blazek, Stanislav Misak e Nasim Ullah. "Numerical Investigation of Photo-Generated Carrier Recombination Dynamics on the Device Characteristics for the Perovskite/Carbon Nitride Absorber-Layer Solar Cell". Nanomaterials 12, n. 22 (15 novembre 2022): 4012. http://dx.doi.org/10.3390/nano12224012.

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The nitrogenated holey two-dimensional carbon nitride (C2N) has been efficaciously utilized in the fabrication of transistors, sensors, and batteries in recent years, but lacks application in the photovoltaic industry. The C2N possesses favorable optoelectronic properties. To investigate its potential feasibility for solar cells (as either an absorber layer/interface layer), we foremost detailed the numerical modeling of the double-absorber-layer–methyl ammonium lead iodide (CH3NH3PbI3) –carbon nitride (C2N) layer solar cell and subsequently provided in-depth insight into the active-layer-associated recombination losses limiting the efficiency (η) of the solar cell. Under the recombination kinetics phenomena, we explored the influence of radiative recombination, Auger recombination, Shockley Read Hall recombination, the energy distribution of defects, Band Tail recombination (Hoping Model), Gaussian distribution, and metastable defect states, including single-donor (0/+), single-acceptor (−/0), double-donor (0/+/2+), double-acceptor (2/−/0−), and the interface-layer defects on the output characteristics of the solar cell. Setting the defect (or trap) density to 1015cm−3 with a uniform energy distribution of defects for all layers, we achieved an η of 24.16%. A considerable enhancement in power-conversion efficiency ( η~27%) was perceived as we reduced the trap density to 1014cm−3 for the absorber layers. Furthermore, it was observed that, for the absorber layer with double-donor defect states, the active layer should be carefully synthesized to reduce crystal-order defects to keep the total defect density as low as 1017cm−3 to achieve efficient device characteristics.

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Lausch, Dominik, Ronny Bakowskie, Michael Lorenz, S. Schweizer, Kai Petter e Christian Hagendorf. "Classification of Recombination-Active Defects in Multicrystalline Solar Cells Made from Upgraded Metallurgical Grade (UMG) Silicon". Solid State Phenomena 178-179 (agosto 2011): 88–93. http://dx.doi.org/10.4028/www.scientific.net/ssp.178-179.88.

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In this contribution a classification of recombination active defects in multicrystalline silicon solar cells made from electronic grade (eg) and upgraded metallurgical grade (umg) silicon feedstock is introduced. On a macroscopic scale the classification is performed by using forward and reversed biased electroluminescence imaging (EL / ReBEL) and imaging of sub-band defect luminescence (ELsub). The luminescence behavior due to structural defects already present in the wafer can be divided into two groups based on their recombination and prebreakdown behavior. As a first step towards a more detailed analysis of the cause for these differences, the classification was also performed on microscopic scale. For this ReBEL and ELsub was performed under an optical microscope (µReBEL/µELsub) and EL was replaced by Electron Beam Induced Current (EBIC). The defect types observed on a macroscopic scale could also be observed on a microscopic scale; however, a third defect type had to be introduced. Finally we propose a qualitative model for the different classified types of recombination active defect structures that can explain the observed recombination and prebreakdown behavior.

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Xu, Xin, Zhenyuan Wu, Zebin Zhao, Zhengli Lu, Yujia Gao, Xi Huang, Jiawei Huang et al. "First-principles study of detrimental iodine vacancy in lead halide perovskite under strain and electron injection". Applied Physics Letters 121, n. 9 (29 agosto 2022): 092106. http://dx.doi.org/10.1063/5.0107441.

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Vacancy defects are universally regarded to be the main defect that limits the photoelectric conversion efficiency of perovskite solar cells. In perovskite, iodine vacancy dominates the defect proportion due to its low formation energy. However, the defect property of iodine vacancy (VI) is still in dispute. Ideally, the VI defect is considered to be a shallow level defect near conduction band minimum, meaning that it does not act as a Shockley–Read–Hall (SRH) nonradiative recombination center. Herein, we find a direct correlation between compressive strain and VI defect behavior. The compressive strain along the lattice vector b/c direction will drive the VI defect from shallow level to deep level defect, which is related to the formation of Pb-dimer. In addition, the influence of extra electrons is also considered during the structural evolution of VI, which is often observed in the experiments. Therefore, we find that the elimination of compressive strain and extra electrons can be of great significance for improving the photoelectric performance of perovskite solar cells. Our work reveals the defect properties of VI from shallow level one to the SRH recombination center and the inherent physics mechanism of defect evolution under external factors, which provides a strategy to control device defects and eliminate recombination losses.

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Voronkov, Vladimir V., e Robert Falster. "Light-Induced Boron-Oxygen Recombination Centres in Silicon: Understanding their Formation and Elimination". Solid State Phenomena 205-206 (ottobre 2013): 3–14. http://dx.doi.org/10.4028/www.scientific.net/ssp.205-206.3.

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Lifetime-degrading recombination centres those that emerge in the presence of excess carriers in boron and oxygen containing silicon - show a peculiar dependence on the concentrations of the relevant impurities, B and O, and on the hole concentrationp0(net doping) in materials that contain compensating donors (phosphorus or Thermal Donors) or added Ga acceptors. The data indicate involvement of both substitutional (Bs) and interstitial (Bi) boron atoms in the major recombination centres observed in p-Si. A suggested model ascribes degradation to the presence of a BiBsO latent defect inherited from the thermal history in a recombination-inactive atomic configuration. In the presence of excess electrons, this latent defect reconfigures into a recombination-active centre. The defect concentration dependence on the material parameters is reduced, in some special cases, to a proportionality top0[2or to [ [2. The essential feature is an involvement of a fast-diffusing species Biin the defect. This species can be removed to the boron nanoprecipitates thus eliminating the defects responsible for the degradation.

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Storasta, L., F. H. C. Carlsson, Peder Bergman e Erik Janzén. "Recombination Enhanced Defect Annealing in 4H-SiC". Materials Science Forum 483-485 (maggio 2005): 369–72. http://dx.doi.org/10.4028/www.scientific.net/msf.483-485.369.

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Recombination enhanced defect annealing of intrinsic defects in 4H-SiC, created by low energy electron irradiation, has been observed. A reduction the defect concentration at temperature lower than the normal annealing temperature of 400º C and 800°C is observed after either above bandgap laser excitation or forward biasing of a pin-diode. The presence of the defects has been studied both electrically and optically using capacitance transient spectroscopy and low temperature photoluminescence. Photoluminescence measurements show that several lines, normally detected after electron irradiation, have almost or entirely disappeared by recombination enhanced annealing at room temperature. From capacitance transient measurements, the annealing enhancement is found to be largest for the HS2 hole trap, while the EH1 and EH3 electron traps also anneal out by recombination enhanced reaction but at a lower rate.

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Klein, Paul B., Rachael L. Myers-Ward, Kok Keong Lew, Brenda L. VanMil, Charles R. Eddy, D. Kurt Gaskill, Amitesh Shrivastava e Tangali S. Sudarshan. "Temperature Dependence of the Carrier Lifetime in 4H-SiC Epilayers". Materials Science Forum 645-648 (aprile 2010): 203–6. http://dx.doi.org/10.4028/www.scientific.net/msf.645-648.203.

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The temperature dependence of the carrier lifetime was measured in n-type 4H-SiC epilayers of varying Z1/2 deep defect concentrations and layer thicknesses in order to investigate the recombination processes controlling the carrier lifetime in low- Z1/2 material. The results indicate that in more recently grown layers with lower deep defect concentrations, surface recombination tends to dominate over carrier capture by other bulk defects. Low-injection lifetime measurements were also found to provide a convenient method to assess the surface band bending and surface trap density in samples with a significant surface recombination rate.

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Пещерова, С. М., Е. Б. Якимов, А. И. Непомнящих, В. И. Орлов, О. В. Феклисова, Л. А. Павлова e Р. В. Пресняков. "Зависимость объемных электрофизических свойств мультикремния от параметров разориентации зерен". Физика и техника полупроводников 53, n. 1 (2019): 59. http://dx.doi.org/10.21883/ftp.2019.01.46988.8814.

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AbstractThe recombination activity of intragrain defects in multicrystalline silicon is investigated by the electron or laser beam induced current methods. The interrelation of the grain orientation with the character of the distribution of intragrain defects (dislocations and impurity inclusions) and their recombination activity is revealed. The defect grain structure is investigated using various etching procedures to reveal the defects. It is shown that the defect density and distribution in the grains depend on their orientation relative the growth axis. Therefore, it is intragrain defects and impurities that are to a large degree responsible for degradation of the nonequilibrium carrier lifetime when compared with grain boundaries.

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Grant, Nicholas E., Fiacre E. Rougieux e Daniel Macdonald. "Low Temperature Activation of Grown-In Defects Limiting the Lifetime of High Purity n-Type Float-Zone Silicon Wafers". Solid State Phenomena 242 (ottobre 2015): 120–25. http://dx.doi.org/10.4028/www.scientific.net/ssp.242.120.

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We investigate the recombination activity of a bulk silicon defect limiting the lifetime of high qualityn-type float-zone (FZ) silicon wafers. By isochronal annealing between 200 and 1100 °C, a defect was found to become activated upon annealing at 450–700 °C, causing an order of magnitude reduction in the bulk lifetime. From photoluminescence imaging, it was evident that recombination active circular patterns were present in these low lifetime samples, suggesting the defect (s) originates from the growth conditions of the ingot. When the samples were passivated by SiNx:H films, a substantial improvement in the bulk lifetime resulted, which we postulate occurred due to hydrogenation of the bulk defects. In contrast, when the samples were annealed at high temperatures (800–1100 °C), the circular recombination active patterns were removed, and the bulk lifetime improved, with the highest lifetime achieved at an annealing temperature of 1100 °C. The experimental results suggest that the defect limiting the lifetime in this FZ material is related to a lattice-impurity defect, which can be permanently annihilated upon annealing at >1100 °C.

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Harada, Tomoki, Tetsuo Ikari e Atsuhiko Fukuyama. "Development of laser heterodyne photothermal displacement method for mapping carrier nonradiative recombination centers in semiconductors". Journal of Applied Physics 131, n. 19 (21 maggio 2022): 195701. http://dx.doi.org/10.1063/5.0085041.

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The laser heterodyne photothermal displacement (LH-PD) method was used to characterize the nonradiative recombination centers of semiconductors, such as defects and deep-lying electronic levels. When a semiconductor surface is irradiated with a modulated continuous wave laser, the irradiated area is periodically heated and expanded owing to the nonradiative recombination of the photoexcited carriers. The LH-PD can measure an absolute value of surface displacement and its time variation at various excitation beam frequencies [Formula: see text]. Si and GaAs substrate samples were used to confirm the usefulness of the proposed method. The obtained time variation of the surface displacement was well explained by theoretical calculations considering the carrier generation, diffusion, recombination, heat diffusion, and generated thermal strain. Because nonradiative carrier recombination generates local heat at defects in semiconductors, the LH-PD technique is useful for analyzing defect distributions. Additionally, measurements of intentional Fe-contaminated Si samples confirmed that this technique is suitable for defect mapping. Displacement mapping with changing [Formula: see text] suggests the potential to measure the distribution of nonradiative recombination centers in the sample depth direction.

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Hara, Tomohiko, e Yoshio Ohshita. "Analysis of recombination centers near an interface of a metal–SiO₂–Si structure by double carrier pulse deep-level transient spectroscopy". AIP Advances 12, n. 9 (1 settembre 2022): 095316. http://dx.doi.org/10.1063/5.0106319.

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This paper proposes a new double carrier pulse deep-level transient spectroscopy (DC-DLTS) method that is applicable for evaluating metal–insulator–semiconductor (MIS) structures and the recombination centers in carrier-selective contact solar cells. Specifically, this study evaluated recombination characteristics of defects induced in bulk Si near SiO2/Si interfaces by reactive plasma deposition (RPD). In this method, a pulse voltage was first applied to inject majority carriers. Subsequently, a second pulse voltage was applied, which allowed minority carriers to be injected into the MIS structure. With these two types of carrier injections, carriers were recombined in recombination-active defects, and the DC-DLTS spectrum changed. During the injection of minority carriers, some majority carriers were thermally emitted from the defects, resulting in a decrease in the signal intensity. The recombination activity was analyzed by considering the effect of thermal emission on the change in signal intensity. The number of induced defect types and defect properties were estimated using Bayesian optimization. According to the results, three types of electron traps were generated using the RPD process. Based on the DC-DLTS results, defects with energy level 0.57 eV below the conduction band and capture cross section of ∼10−15 cm2 act as recombination centers.

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Tesi sul tema "Defect recombination"

Puttisong, Yuttapoom. "Spin-dependent Recombination in GaNAs". Thesis, Linköping University, Linköping University, Department of Physics, Chemistry and Biology, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-19355.

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Spin filtering properties of novel GaNAs alloys are reported in this thesis. Spin-dependent recombination (SDR) in GaNAs via a deep paramagnetic defect center is intensively studied. By using the optical orientation photoluminescence (PL) technique, GaNAs is shown to be able to spin filter electrons injected from GaAs, which is a useful functional property for integratition with future electronic devices. The spin filtering ability is found to degrade in narrow GaNAs quantum well (QW) structures which is attributed to (i) acceleration of band-to-band recombination competing with the SDR process and to (ii) faster electron spin relaxation in the narrow QWs. Ga interstitial-related defect centers have been found to be responsible for the SDR process by using the optically detected magnetic resonance (ODMR) technique. The defects are found to be the dominant grown-in defects in GaNAs, commonly formed during both MBE and MOCVD growths. Methods to control the concentration of the Ga interstitials by varying doping, growth parameters and post-growth treatments are also examined.

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Thomas, Mélissa. "Origins of Cellular Lethality Resulting From a Defect in Homologous Recombination in Human Cells". Thesis, université Paris-Saclay, 2021. http://www.theses.fr/2021UPASL027.

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La recombinaison homologue (RH) est impliquée dans la réparation des cassures double brin à l'ADN, et dans la gestion des fourches de réplication bloquées. Rad51 et BRCA2 en sont deux protéines pivots.J'ai montré que l'inhibition de la RH ainsi que la surexpression de Rad51 sont létales dans les cellules humaines, mais qu'un faible nombre de cellules arrivent à survivre. De plus, dans plusieurs cancers, les gènes de la RH sont mutés (BRCA1/2 dans les cancers du sein et de l'ovaire) ou la surexpression d'un gène de la RH est observée. Mon projet a pour but d'identifier les mécanismes et les causes de la létalité induite par une dérégulation de la RH dans les cellules humaines, ainsi que de comprendre comment certaines cellules arrivent à y survivre. L’analyse du cycle cellulaire et du marquage Histone H3 phosphorylée a révélé que les cellules humaines inactivées pour la RH ou surexprimant RAD51 s’accumulent à la transition G2/M. Parallèlement la vidéomicroscopie a suggéré que les cellules mourraient par apoptose, ce qui a été corroboré par des expériences utilisant l'Annexin-V comme marqueur d’apoptose et par des Western-Blot. Les Western Blots montrent que le checkpoint G2/M est activé, via l'analyse de la cyclineB1 et de cdk1, et que l'apoptose est déclenchée, via l'analyse du clivage de PARP. Mon hypothèse principale de travail étant que la surexpression d'un dominant négatif de Rad51 et possiblement la surexpression du Rad51 WT, entraîne des défauts de réplication dont l'accumulation entraînerait une activation du checkpoint. Des expériences d'incorporation de BrdU et de peignage moléculaire sont venus confirmer mon hypothèse : dans les cellules ayant une dérégulation de la RH, la vitesse de réplication est diminuée et il y a plus de fourches bloquées. Des analyses in-silico ont révélées que les cancers mutés dans la RH sont fréquemment co-mutés dans des gènes impliqués dans le checkpoint G2/M ou dans le redémarrage des fourches. Une liste de gènes candidats, enrichie de résultats de séquençages de fibroblastes de patients FANCD1, a été testée, confirmant l'analyse in-silico
Homologous recombination (HR) is involved in repairing DNA double strand breaks, and in protecting and restarting stalled or collapsed replication forks. Rad51 and BRCA2 are two key proteins of HR. I have showed that inhibiting HR, as well as over expressing Rad51, is lethal in human cells, although a very few cells still survive the inhibition. Moreover, many cancers carry mutations in an HR gene (BRCA1/2 in breast and ovary cancers) or over express an HR gene. My project aims to identify the mechanisms and the causes behind the lethality triggered by a dysregulation of HR, and to understand how a few cells manage to survive it. I have determined, through FACS and phosphorylated histone H3 labeling (IF), that HR deficient human cells, or those over expressing Rad51, accumulate at the G2/M checkpoint.At the same time, time-lapse microscopy experiments seemed to indicate that the cells died from apoptosis, which was confirmed by data from experiments using Annexin-V as an apoptosis marker and from Western-Blots. Western-Blots showed that the G2/M checkpoint is activated, through analysis of CyclinB1 and of cdk1, and that apoptosis is triggered, through analysis of PARP cleavage. My main working hypothesis was that overexpressing a dominant negative form of Rad51, and possibly also overexpressing Rad51 WT, would lead to replication defects, whose accumulation would in turn lead to an activation of the checkpoint. BrdU incorporation experients and use of the molecular combing technique confirmed this hypothesis : in HR-dysregulated cells, replication speed is slowed down and there are more stalled forks. In-silico analyses have showed that HR-mutated cancers often carry a second mutation in another gene, involved in either the G2/M checkpoint or in restarting stalled replication forks. Based on these analyses and on results from RNAseq experiments performed on FANCD1 patients' fibroblasts, candidate genes have already been listed, confirming the in-silico analysis

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Turcu, Mircea Cassian. "Defect energies, band alignments, and charge carrier recombination in polycrystalline Cu(In,Ga)(Se,S)2 alloys". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2004. http://nbn-resolving.de/urn:nbn:de:swb:14-1086247686828-95497.

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This work investigates the defect energies, band alignments, and charge carrier recombination in polycrystalline Cu(In1-xGax)(Se1-ySy)2 chalcopyrite thin films and the interrelationship with the alloy composition. Photoluminescence spectroscopy of investigated Cu-poor Cu(In,Ga)(Se,S)2 layers generally shows broad emission lines with the corresponding maxima shifting towards higher energies under decreasing temperature or under increasing excitation power. Admittance spectroscopy of Cu-poor ZnO/CdS/Cu(In,Ga)(Se,S)2 chalcopyrite devices shows that the activation energies of the dominant defect distributions involving donors at the CdS/absorber interface and deep acceptors in the chalcopyrite bulk, increase upon alloying CuInSe2 with S. The band alignments within the Cu(In1-xGax)(Se1-ySy)2 system are determined using the energy position of the bulk acceptor state as a reference. The band gap enlargement under Ga alloying is accommodated almost exclusively in the rise of the conduction band edge, whereas the increase of band gap upon alloying with S is shared between comparable valence and conduction band offsets. The extrapolated band discontinuities [delta]EV(CuInSe2/CuInS2) = -0.23 eV, [delta]EC(CuInSe2/CuInS2) = 0.21 eV, [delta]EV(CuInSe2/CuGaSe2) = 0.036 eV, and [delta]EC(CuInSe2/CuGaSe2) = 0.7 eV are in good agreement with theoretical predictions. Current-voltage analysis of Cu-poor ZnO/CdS/Cu(In,Ga)(Se,S)2 devices reveals recombination barriers which follow the band gap energy of the absorber irrespective of alloy composition, as expected for dominant recombination in the chalcopyrite bulk. In turn, the recombination at the active junction interface prevails in Cu-rich devices which display substantially smaller barriers when compared to the band gap energy of the absorber. The result indicates that the Cu-stoichiometry is the driving compositional parameter for the charge carrier recombination in the chalcopyrite heterojunctions under investigations.

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Turcu, Mircea Cassian. "Defect energies, band alignments, and charge carrier recombination in polycrystalline Cu(In,Ga)(Se,S)2 alloys". Doctoral thesis, Technische Universität Dresden, 2003. https://tud.qucosa.de/id/qucosa%3A24342.

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Santos, Samantha Fonseca dos. "Theoretical and computational studies of dissociative recombination of H₃⁺ with low kinetic energy electrons time-independent and time-dependent approach /". Orlando, Fla. : University of Central Florida, 2009. http://purl.fcla.edu/fcla/etd/CFE0002668.

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PATRIZI, LAURA. "ANALYSIS OF B LYMPHOCYTES IN MOUSE MODEL LIGASE IV WITH HYPOMORPHIC MUTATION IN VDJ RECOMBINATION ASSOCIATED WITH GROWTH DEFECT". Doctoral thesis, Università degli Studi di Milano, 2010. http://hdl.handle.net/2434/150193.

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The major mechanism for the repair of DNA doublestrand breaks (DSBs) in mammalian cells is non-homologous end-joining (NHEJ), a process that involves the DNA-dependent protein kinase , XRCC4 and DNA ligase IV. Rodent cells and mice defective in these components are radiation-sensitive and defective in V(D)J-recombination, showing that NHEJ also functions to rejoin DSBs introduced during lymphocyte development. We have generated a knock-in mouse model with a homozygous Lig4 arginine to histidine (R278H) mutation that corresponds to the mutation identified in the first LIG4-deficient patient, who developed T cell leukemia associated with increased cellular radiosensitivity. The clinical presentation of the syndrome is complex and heterogeneous and may include varying degrees of lymphopenia, growth retardation and microcephaly. The phenotypic effects of the impaired repair of non programmed DNA damage are more diverse and difficult to study. Although such defects in cell survival and proliferation are likely to have an impact on the immune system, their contribution to the immunodeficiency of the LigIV syndrome remains unknown.

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Lam, N. D., S. Kim, J. J. Lee, K. R. Choi, M. H. Doan e H. Lim. "Enhanced Luminescence of InGaN / GaN Vertical Light Emitting Diodes with an InGaN Protection Layer". Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35210.

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We have investigated the effectiveness of a thin n-In0.2Ga0.8N layer inserted in the bottom n-GaN layer of InGaN/GaN blue light emitting diodes (LEDs) for the protection of multiple quantum wells during the laser lift-off process for vertical LED fabrication. The photoluminescence properties of the InGaN/GaN lateral LEDs are nearly identical irrespective of the existence of the n-In0.2Ga0.8N insertion layer in the bottom n-GaN layer. However, such an insertion is found to effectively increase the photoluminescence intensity of the multiple quantum well and the carrier lifetime of the vertical LEDs. These improvements are attributed to the reduced defect generations in the vertical LEDs during the laser lift-off process due to the presence of the protection layer. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35210

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Turcu, Mircea C. [Verfasser]. "Defect energies, band alignments, and charge carrier recombination in polycrystalline Cu(In,Ga)(Se,S)2 alloys / Mircea C Turcu". Aachen : Shaker, 2004. http://d-nb.info/1170529550/34.

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Steingrube, Silke [Verfasser]. "Recombination models for defects in silicon solar cells / Silke Steingrube". Hannover : Technische Informationsbibliothek und Universitätsbibliothek Hannover (TIB), 2011. http://d-nb.info/1015460577/34.

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RUCCI, FRANCESCA. "Murine models of hypomorphic defects of v(d)j recombination". Doctoral thesis, Università degli Studi di Milano, 2009. http://hdl.handle.net/2434/155853.

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V(D)J recombination is the process by which the subgenic elements of T and B cell receptors are assembled. The Rag1 and Rag2 proteins initiate this process by cleaving the DNA, whereas the Non Homologous End-Joining pathway (that includes Ku70/80, XRCC4, LigIV, DNA-PKcs and Cernunnos)mediates DNA joining. Rag1 and Rag2 null mutations cause SCID with complete lack of T and B lymphocytes in humans. Hypomorphic mutations that reduce, but do not abrogate, V(D)J recombination activity, may lead to Omenn syndrome (OS) or to “leaky SCID”, both of which are characterized by activated, anergic and autologous T cells, whereas severe erythroderma and cholitis are typical of OS only. Hypomorphic LigIV mutations in humans are associated with increased cellular radiosensitivity, microcephaly, facial dysmorphisms, growth retardation, developmental delay, and a variable degree of immunodeficiency. These disorders define the LIGIV syndrome. The work presented in this thesis focused on the characterization of two murine models with hypomorphic mutations in Rag1 (rag1S723C/S723C) and LigIV (ligIVR278H/R278H) that recapitulate leaky SCID. A minority of rag1S723C/S723C mice (but none of ligIVR278H/R278H mice) showed features of OS without phenotypic features of OS. Both mouse models show a severe, but incomplete, block in T and B cell development, with residual generation of single-positive thymocytes. However, peripheral T cells are present and show an activated and anergic phenotype, with a restricted repertoire, reminiscent of human leaky SCID. The impaired in vitro proliferation in response to anti-CD3 is mostly due to increased apoptosis, and can be only partially rescued by addition of costimulatory factors such as anti-CD28 or by exogenous IL-2. Despite a severe block at the pro to pre-B stage of B cell differentiation and of profound B cell lymphopenia, IgG, IgM, IgA and IgE serum levels are maintained, and a high proportion of immunoglobulin-secreting cells was observed in the spleen of both rag1S723C/S723C and ligIVR278H/R278H mice. Antibody responses to T-dependent and T-independent antigens are impaired, however both hypomorphic mouse models spontaneously produce high amounts of low-affinity antibodies that include self-reactive specificities. The Rag1 and LigIV hypomorphic mouse models show attempts to organize the thymic medulla and are able, to various degrees, to generate nTregs. However, the expression of aire and of tissue-rectricted antigens, required for the maintenance of the central tolerance, is reduced. Taken together, these data indicate that the stochastic generation of an autoreactive B cell repertoire, associated with defects in central and peripheral T cell tolerance, are an important component of the immunopathology of immunodeficiencies associated with hypomorphic mutation in the V(D)J recombination process. Therefore using these mouse models, it is now possible to elucidate the mechanisms underlying the phenotypic variability between OS and leaky SCID in humans.

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Più fonti

Libri sul tema "Defect recombination"

Orton, J. W. The electrical characterization of semiconductors: Measurement of minority carrier properties. London: Academic Press, 1990.

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Davidson, J. A. Minority carrier processes and recombination at point and extended defects in silicon. Manchester: UMIST, 1996.

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Multiphonon Recombination at Defects in Semiconductors. University of Cambridge ESOL Examinations, 2002.

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Orton, J. W., e P. Blood. The Electrical Characterization of Semiconductors: Measurement of Minority Carrier Properties (Techniques of Physics). Academic Press, 1992.

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Voll, Reinhard E., e Barbara M. Bröker. Innate vs acquired immunity. Oxford University Press, 2013. http://dx.doi.org/10.1093/med/9780199642489.003.0048.

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The innate and the adaptive immune system efficiently cooperate to protect us from infections. The ancient innate immune system, dating back to the first multicellular organisms, utilizes phagocytic cells, soluble antimicrobial peptides, and the complement system for an immediate line of defence against pathogens. Using a limited number of germline-encoded pattern recognition receptors including the Toll-like, RIG-1-like, and NOD-like receptors, the innate immune system recognizes so-called pathogen-associated molecular patterns (PAMPs). PAMPs are specific for groups of related microorganisms and represent highly conserved, mostly non-protein molecules essential for the pathogens' life cycles. Hence, escape mutants strongly reduce the pathogen's fitness. An important task of the innate immune system is to distinguish between harmless antigens and potentially dangerous pathogens. Ideally, innate immune cells should activate the adaptive immune cells only in the case of invading pathogens. The evolutionarily rather new adaptive immune system, which can be found in jawed fish and higher vertebrates, needs several days to mount an efficient response upon its first encounter with a certain pathogen. As soon as antigen-specific lymphocyte clones have been expanded, they powerfully fight the pathogen. Importantly, memory lymphocytes can often protect us from reinfections. During the development of T and B lymphocytes, many millions of different receptors are generated by somatic recombination and hypermutation of gene segments making up the antigen receptors. This process carries the inherent risk of autoimmunity, causing most inflammatory rheumatic diseases. In contrast, inadequate activation of the innate immune system, especially activation of the inflammasomes, may cause autoinflammatory syndromes.

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Capitoli di libri sul tema "Defect recombination"

Storasta, L., F. H. C. Carlsson, J. Peder Bergman e Erik Janzén. "Recombination Enhanced Defect Annealing in 4H-SiC". In Materials Science Forum, 369–72. Stafa: Trans Tech Publications Ltd., 2005. http://dx.doi.org/10.4028/0-87849-963-6.369.

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Redfield, David. "Recombination-Enhanced Defect Formation and Annealing in a-Si:H". In Disordered Semiconductors, 635–40. Boston, MA: Springer US, 1987. http://dx.doi.org/10.1007/978-1-4613-1841-5_67.

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Takagi, Hidekazu. "Extension of the Quantum Defect Theory and Its Application to Electron and Molecular Ion Collisions". In Dissociative Recombination of Molecular Ions with Electrons, 177–86. Boston, MA: Springer US, 2003. http://dx.doi.org/10.1007/978-1-4615-0083-4_17.

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Marino, F., S. Gialanella e R. Delorenzo. "Defect Recombination Phenomena in Melt-Spun Ordered Alloys of the Fe-Al System". In Ordering and Disordering in Alloys, 155–63. Dordrecht: Springer Netherlands, 1992. http://dx.doi.org/10.1007/978-94-011-2886-5_16.

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van der Burg, Mirjam, Andrew R. Gennery e Qiang Pan-Hammarström. "Class-Switch Recombination Defects". In Humoral Primary Immunodeficiencies, 179–99. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-91785-6_15.

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Durandy, A., e Sven Kracker. "Immunoglobulin Class Switch Recombination Defects". In Encyclopedia of Medical Immunology, 385–92. New York, NY: Springer New York, 2020. http://dx.doi.org/10.1007/978-1-4614-8678-7_34.

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Durandy, A., e S. Kracker. "Immunoglobulin Class Switch Recombination Defects". In Encyclopedia of Medical Immunology, 1–7. New York, NY: Springer New York, 2019. http://dx.doi.org/10.1007/978-1-4614-9209-2_34-1.

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Bryant, Helen E., e Sydney Shall. "Synthetic Lethality with Homologous Recombination Repair Defects". In Cancer Drug Discovery and Development, 315–44. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-14151-0_13.

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Kracker, Sven, Pauline Gardës e Anne Durandy. "Inherited Defects of Immunoglobulin Class Switch Recombination". In Advances in Experimental Medicine and Biology, 166–74. New York, NY: Springer New York, 2010. http://dx.doi.org/10.1007/978-1-4419-6448-9_15.

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Wilshaw, P. R., T. S. Fell e G. R. Booker. "Recombination at Dislocations in Silicon and Gallium Arsenide". In Point and Extended Defects in Semiconductors, 243–56. Boston, MA: Springer US, 1989. http://dx.doi.org/10.1007/978-1-4684-5709-4_18.

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Atti di convegni sul tema "Defect recombination"

Benchiheb, Nedjoua, Asma Benchiheb, Yasmina Saidi e Hamza Lidjici. "Emitter Thickness and Solar Cell Efficiency: The Role of Deep-Level Defects and Auger Recombination". In 2024 3rd International Conference on Advanced Electrical Engineering (ICAEE), 1–7. IEEE, 2024. https://doi.org/10.1109/icaee61760.2024.10783184.

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Seghier, D., T. M. Arinbjarnason e H. P. Gislason. "Deep-defect related generation-recombination noise in GaAs". In 2004 13th International Conference on Semiconducting and Insulating Materials. IEEE, 2004. http://dx.doi.org/10.1109/sim.2005.1511426.

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Lee, Jin Hee, e Je-Hyung Kim. "Point and planar defect complex in SiC nanowires for high-performance quantum emitters". In Integrated Photonics Research, Silicon and Nanophotonics. Washington, D.C.: Optica Publishing Group, 2022. http://dx.doi.org/10.1364/iprsn.2022.iw2b.5.

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We investigate SiC nanowires that host point defects coupled to a few-layered stacking fault. These point-planar defect complexes exhibit outstanding optical properties of high brightness, fast recombination time, and a high Debye-Waller factor.

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Khaital, Yu L., Joseph Salzman e R. Beserman. "Kinetics of gradual degradation in semiconductor lasers". In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1988. http://dx.doi.org/10.1364/oam.1988.mj7.

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Gradual degradation in semiconductor lasers is caused by the creation and migration of point defects which require jumping of atoms from their initial position to disordered ones (with activation energy E a of a few electron volts). The injection of a nonequilibrium electron-hole plasma may increase the probability of structural changes and reduce their activation energy by δE ≃ F c − F v through nonradiative recombination1 (F c and F v are the quasi-Fermi levels). Such enhancement is possible only if the recombination is synchronized with the atom jump event, and the released energy δE is localized around this atom. In the present model, such synchronization is inherent: the fluctuating atom forms a transient point defect which behaves as a nonradiative recombination center of lifetime δ τ ≃ 10−13 − 10−12s. Free carriers are trapped at these centers leading to synchronous release of localized energy δE. This model is based on the kinetic many-body theory of short-lived large energy fluctuations of atoms.2,3 The laser degradation rate K is given by K = K o exp[−(E a − δE)/kT] with K o and δE expressed in terms of the laser parameters (carrier concentration, energy gap, defect concentration, etc.) Calculated laser lifetimes are in good agreement with experimental data.

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Bonfiglió, A., M. Vanzi, M. B. Casu, F. Magistrali, M. Maini e G. Salmini. "Interpretation of Sudden Failures in Pump Laser Diodes". In ISTFA 1997. ASM International, 1997. http://dx.doi.org/10.31399/asm.cp.istfa1997p0189.

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Abstract The occurrence of sudden failures has been reported for 980 nm SL SQW InGaAs pump lasers. The post-mortem analysis reveals failure modes that are consistent with the formation of defects at the active area. The problem calls for two separate efforts: monitoring the degradation at suitable time resolution and structural characterization of defects. This article reports about the optical power and overall voltage monitoring results during a constant current lifetest, in which "sudden failures" switched off the lasers in a few hours, after 1500 hours of regular life, and about their interpretation based on TEM cross-sectional images across an EBIC-detected high recombination site. The hypothesis that Recombination Enhanced Defect Reaction (REDR) is a suitable mechanism for defect growth in forward biased GaAs-based diodes is proposed and discussed that REDR is the origin of the observed sudden failures, starting from native defects located in "cool" regions.

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Lee, Jin Hee, e Je-Hyung Kim. "Strong Zero-Phonon Transition from Defects in SiC Nanowires with Stacking Faults". In Quantum 2.0. Washington, D.C.: Optica Publishing Group, 2023. http://dx.doi.org/10.1364/quantum.2023.qw2a.27.

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We study SiC nanowires that host point defects coupled to a few-layered stacking fault. These point-planar defect complexes exhibit outstanding optical properties of high brightness, fast recombination time, and a high Debye-Waller factor.

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Askari, Syed Sadique Anwer, Manoj Kumar e Mukul Kumar Das. "Effects of Interface defect on the performance of ZnO/p-Si heterojunction solar cell". In JSAP-OSA Joint Symposia. Washington, D.C.: Optica Publishing Group, 2017. http://dx.doi.org/10.1364/jsap.2017.6p_a410_12.

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The study and optimization of emitter zinc oxide/crystalline silicon heterointerface with a focus on recombination has been identified as the most important issue to fully utilize the potential of ZnO/Si heterojunction solar cell [1]. ZnO/Si interface properties are very crucial to the performance of solar cell due to the fact that the interface is located inside the space charge region. Front surface recombination of Si or the interface recombination velocity of ZnO/Si interface is the most important parameter in this simulation that dictates the efficiency of solar cell. It is known that the open circuit voltage (Voc) of the cell with the negative band offset at the absorber/emitter interface may be limited by interface recombination [2].

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Verezub, N., e A. Prostomolotov. "DEFECT FORMATION IN DISLOCATION-FREE SILICON SINGLE CRYSTALS". In Mathematical modeling in materials science of electronic component. LCC MAKS Press, 2022. http://dx.doi.org/10.29003/m3091.mmmsec-2022/132-135.

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The physical concepts of defect formation processes in dislocation-free silicon single crystals are discussed. Mathematical models of these processes are considered for various temperature ranges realized during their growth. Near the crystallization temperature, the processes of fast recombination and transfer of intrinsic point defects (vacancies and interstitial silicon atoms) are considered in detail, the calculation results of which are verified by the experimental data of the carrier lifetime map in a silicon single crystal 150 mm in diameter grown by Czochralski method

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Racko, J., R. Granzner, P. Benko, M. Mikolasek, L. Harmatha, M. Kittler, F. Schwierz e J. Breza. "Model of coupled defect level recombination with participation of multiphonons". In 2014 10th International Conference on Advanced Semiconductor Devices & Microsystems (ASDAM). IEEE, 2014. http://dx.doi.org/10.1109/asdam.2014.6998674.

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Gfroerer, T. H., P. R. Simov, B. A. West e M. W. Wanlass. "Defect-related trapping and recombination in metamorphic GaAs0.72P0.28 grown on GaAs". In 2008 33rd IEEE Photovolatic Specialists Conference (PVSC). IEEE, 2008. http://dx.doi.org/10.1109/pvsc.2008.4922904.

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Rapporti di organizzazioni sul tema "Defect recombination"

Schild, David, e Claudia Wiese. Overexpressed of RAD51 suppresses recombination defects: a possible mechanism to reverse genomic instability. Office of Scientific and Technical Information (OSTI), ottobre 2009. http://dx.doi.org/10.2172/983266.

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