Articoli di riviste: "Defect recombination"

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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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Kawakita, Shirou, Mitsuru Imaizumi, Shogo Ishizuka, Hajime Shibata, Shigeru Niki, Shuichi Okuda e 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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Gan, Yongjin, Guixin Qiu, Binyi Qin, Xueguang Bi, Yucheng Liu, Guochao Nie, Weilian Ning e Ruizhao Yang. "Numerical Analysis of Stable (FAPbI3)0.85(MAPbBr3)0.15-Based Perovskite Solar Cell with TiO2/ZnO Double Electron Layer". Nanomaterials 13, n. 8 (8 aprile 2023): 1313. http://dx.doi.org/10.3390/nano13081313.

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Although perovskite solar cells have achieved excellent photoelectric conversion efficiencies, there are still some shortcomings, such as defects inside and at the interface as well as energy level dislocation, which may lead to non-radiative recombination and reduce stability. Therefore, in this study, a double electron transport layer (ETL) structure of FTO/TiO2/ZnO/(FAPbI3)0.85(MAPbBr3)0.15/Spiro-OMeTAD is investigated and compared with single ETL structures of FTO/TiO2/(FAPbI3)0.85(MAPbBr3)0.15/Spiro-OMeTAD and FTO/ZnO/(FAPbI3)0.85(MAPbBr3)0.15/Spiro-OMeTAD using the SCAPS-1D simulation software, with special attention paid to the defect density in the perovskite active layer, defect density at the interface between the ETL and the perovskite active layer, and temperature. Simulation results reveal that the proposed double ETL structure could effectively reduce the energy level dislocation and inhibit the non-radiative recombination. The increases in the defect density in the perovskite active layer, the defect density at the interface between the ETL and the perovskite active layer, and the temperature all facilitate carrier recombination. Compared with the single ETL structure, the double ETL structure has a higher tolerance for defect density and temperature. The simulation outcomes also confirm the possibility of preparing a stable perovskite solar cell.

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Lien, Der-Hsien, Shiekh Zia Uddin, Matthew Yeh, Matin Amani, Hyungjin Kim, Joel W. Ager, Eli Yablonovitch e Ali Javey. "Electrical suppression of all nonradiative recombination pathways in monolayer semiconductors". Science 364, n. 6439 (2 maggio 2019): 468–71. http://dx.doi.org/10.1126/science.aaw8053.

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Defects in conventional semiconductors substantially lower the photoluminescence (PL) quantum yield (QY), a key metric of optoelectronic performance that directly dictates the maximum device efficiency. Two-dimensional transition-metal dichalcogenides (TMDCs), such as monolayer MoS2, often exhibit low PL QY for as-processed samples, which has typically been attributed to a large native defect density. We show that the PL QY of as-processed MoS2 and WS2 monolayers reaches near-unity when they are made intrinsic through electrostatic doping, without any chemical passivation. Surprisingly, neutral exciton recombination is entirely radiative even in the presence of a high native defect density. This finding enables TMDC monolayers for optoelectronic device applications as the stringent requirement of low defect density is eased.

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El Hageali, Sami A., Harvey Guthrey, Steven Johnston, Jake Soto, Bruce Odekirk, Brian P. Gorman e Mowafak Al-Jassim. "Nondestructive microstructural investigation of defects in 4H-SiC epilayers using a multiscale luminescence analysis approach". Journal of Applied Physics 131, n. 18 (14 maggio 2022): 185705. http://dx.doi.org/10.1063/5.0088313.

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The development of metal oxide semiconductor field effect transistors (MOSFETs) utilizing epitaxially grown 4H-SiC has accelerated in recent years due to their favorable properties, including a high breakdown field, high saturated electron drift velocity, and good thermal conductivity. However, extended defects in epitaxial 4H-SiC can affect both device yields and operational lifetime. In this work, we demonstrate the importance of a multiscale luminescence characterization approach to studying nondestructively extended defects in epitaxial 4H-SiC semiconducting materials. Multiscale luminescence analysis reveals different aspects of excess charge carrier recombination behavior based on the scale of a particular measurement. Combining measurements of the same extended defect area at different scales tells us more about the essential nature of that defect and its microstructure. Here, we use photoluminescence imaging and cathodoluminescence spectrum imaging to investigate the recombination behavior of several different types of extended defects, including stacking faults, inclusions, and basal plane dislocations. A detailed understanding of the optoelectronic properties of extended defects in epitaxial SiC helps elucidate the microstructure of extended defects and can provide pathways to mitigate detrimental changes during device operation related to their evolution, such as the recombination enhanced dislocation glide effect that affects SiC-based MOSFETs.

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Montenegro, D., V. Hortelano, O. Martínez, M. C. Martínez-Tomas, V. Sallet, V. Muñoz e J. Jiménez. "Non radiative recombination centers in ZnO nanorods". MRS Proceedings 1538 (2013): 317–22. http://dx.doi.org/10.1557/opl.2013.548.

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ABSTRACTNowadays, the nature of the non radiative recombination centres in ZnO is a matter of controversy; they have been related to extended defects, zinc vacancy complexes, and surface defects, among other possible candidates. We present herein the optical characterization of catalyst free ZnO nanorods grown by atmospheric MOCVD by microRaman and cathodoluminescence spectroscopies. The correlation between the defect related Raman modes and the cathodoluminescence emission along the nanorods permits to establish a relation between the non radiative recombination centers and the defects responsible for the local Raman modes, which have been related to Zn interstitial complexes.

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Ogihara, Chisato, Yuta Shintoku, Kei Yamaguchi e Kazuo Morigaki. "Preparation condition and recombination rates at radiative defects in a-Si:H". Canadian Journal of Physics 92, n. 7/8 (luglio 2014): 561–64. http://dx.doi.org/10.1139/cjp-2013-0538.

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Recombination rates at radiative defects in the hydrogenated amorphous silicon films prepared at various preparation conditions, estimated from intensities and characteristic lifetimes of defect photoluminescence, have been investigated. The temperature variations of the radiative recombination rate are discussed in terms of a model in which the increase of the radiative recombination rate is attributed to the thermal excitation of the holes from deep and strongly localised tail states to shallow and more extended tail states. The temperature variations of nonradiative recombination rate are discussed in terms of a theory for the case of strong electron–phonon coupling.

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Fadda, Sarah, Antonio Mario Locci e Francesco Delogu. "Modeling of Point Defects Annihilation in Multilayered Cu/Nb Composites under Irradiation". Advances in Materials Science and Engineering 2016 (2016): 1–17. http://dx.doi.org/10.1155/2016/9435431.

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This work focuses on a mathematical modeling of the response to irradiation of a multilayer composite material. Nonstationary balance equations are utilized to account for production, recombination, transport, and annihilation, or removal, of vacancies and interstitials at interfaces. Although the model developed has general validity, Cu/Nb multilayers are used as case study. Layer thickness, temperature, radiation intensity, and surface recombination coefficients were varied systematically to investigate their effect on point defect annihilation processes at interfaces. It is shown that point defect annihilation at interfaces mostly depends on point defect diffusion. The ability of interfaces to remove point defects can be described by a simple map constructed using only two dimensionless parameters, which provides a general tool to estimate the efficiency of vacancy and interstitial removal in multilayer composite materials.

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Schillgalies, M., A. Laubsch, St Lutgen, A. Avramescu, G. Brüderl, D. Queren e U. Strauss. "Defect-related recombination in InGaN-lasers". physica status solidi (c) 5, n. 6 (maggio 2008): 2192–94. http://dx.doi.org/10.1002/pssc.200778537.

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Zakirov, M. I., e O. A. Korotchenkov. "Carrier recombination in sonochemically synthesized ZnO powders". Materials Science-Poland 35, n. 1 (23 aprile 2017): 211–16. http://dx.doi.org/10.1515/msp-2017-0016.

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AbstractZnO powders with particle size in the nm to μm range have been fabricated by sonochemical method, utilizing zinc acetate and sodium hydroxide as starting materials. Carrier recombination processes in the powders have been investigated using the photoluminescence, FT-IR and surface photovoltage techniques. It has been shown that the photoluminescence spectra exhibit a number of defect-related emission bands which are typically observed in ZnO lattice and which depend on the sonication time. It has been found that the increase of the stirring time results in a faster decay of the photovoltage transients for times shorter than approximately 5 ms. From the obtained data it has been concluded that the sonication modifies the complicated trapping dynamics from volume to surface defects, whereas the fabrication method itself offers a remarkably convenient means of modifying the relative content of the surface-to-volume defect ratio in powder grains and altering the dynamics of photoexcited carriers.

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Kaytor, M. D., e D. M. Livingston. "Saccharomyces cerevisiae RAD52 alleles temperature-sensitive for the repair of DNA double-strand breaks." Genetics 137, n. 4 (1 agosto 1994): 933–44. http://dx.doi.org/10.1093/genetics/137.4.933.

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Abstract We have screened for mutations of the Saccharomyces cerevisiae RAD52 gene which confer a temperature-sensitive (ts) phenotype with respect to either the repair of DNA lesions caused by methyl methanesulfonate (MMS) or the recombination of an intrachromosomal recombination reporter. We were readily able to isolate alleles ts for the repair of lesions caused by MMS but were unable to find alleles with a severe ts deficiency in intrachromosomal recombination. We extensively characterized four strains conferring ts growth on MMS agar. These strains also exhibit ts survival when exposed to gamma-radiation or when the HO endonuclease is constitutively expressed. Although none of the four alleles confers a severe ts defect in intrachromosomal recombination, two confer significant defects in tests of mitotic, interchromosomal recombination carried out in diploid strains. The mutant diploids sporulate, but the two strains with defects in interchromosomal recombination have reduced spore viability. Meiotic recombination is not depressed in the two diploids with reduced spore viability. Thus, in the two strains with reduced spore viability, defects in mitotic and meiotic recombination do not correlate. Sequence analysis revealed that in three of the four ts alleles the causative mutations are in the first one-third of the open reading frame while the fourth is in the C-terminal third.

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Chu, Weibin, Qijing Zheng, Oleg V. Prezhdo, Jin Zhao e Wissam A. Saidi. "Low-frequency lattice phonons in halide perovskites explain high defect tolerance toward electron-hole recombination". Science Advances 6, n. 7 (febbraio 2020): eaaw7453. http://dx.doi.org/10.1126/sciadv.aaw7453.

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Low-cost solution-based synthesis of metal halide perovskites (MHPs) invariably introduces defects in the system, which could form Shockley-Read-Hall (SRH) electron-hole recombination centers detrimental to solar conversion efficiency. Here, we investigate the nonradiative recombination processes due to native point defects in methylammonium lead halide (MAPbI3) perovskites using ab initio nonadiabatic molecular dynamics within surface-hopping framework. Regardless of whether the defects introduce a shallow or deep band state, we find that charge recombination in MAPbI3 is not enhanced, contrary to predictions from SRH theory. We demonstrate that this strong tolerance against defects, and hence the breakdown of SRH, arises because the photogenerated carriers are only coupled with low-frequency phonons and electron and hole states overlap weakly. Both factors appreciably decrease the nonadiabatic coupling. We argue that the soft nature of the inorganic lattice with small bulk modulus is key for defect tolerance, and hence, the findings are general to other MHPs.

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Saintigny, Yannick, Kate Makienko, Cristina Swanson, Mary J. Emond e Raymond J. Monnat,. "Homologous Recombination Resolution Defect in Werner Syndrome". Molecular and Cellular Biology 22, n. 20 (15 ottobre 2002): 6971–78. http://dx.doi.org/10.1128/mcb.22.20.6971-6978.2002.

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ABSTRACT Werner syndrome (WRN) is an uncommon autosomal recessive disease whose phenotype includes features of premature aging, genetic instability, and an elevated risk of cancer. We used three different experimental strategies to show that WRN cellular phenotypes of limited cell division potential, DNA damage hypersensitivity, and defective homologous recombination (HR) are interrelated. WRN cell survival and the generation of viable mitotic recombinant progeny could be rescued by expressing wild-type WRN protein or by expressing the bacterial resolvase protein RusA. The dependence of WRN cellular phenotypes on RAD51-dependent HR pathways was demonstrated by using a dominant-negative RAD51 protein to suppress mitotic recombination in WRN and control cells: the suppression of RAD51-dependent recombination led to significantly improved survival of WRN cells following DNA damage. These results define a physiological role for the WRN RecQ helicase protein in RAD51-dependent HR and identify a mechanistic link between defective recombination resolution and limited cell division potential, DNA damage hypersensitivity, and genetic instability in human somatic cells.

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Praepattarapisut, Warakorn, Weera Pengchan, Toempong Phetchakul e Amporn Poyai. "Defect Distribution and Yield Analysis Technique on Silicon Wafer". Advanced Materials Research 911 (marzo 2014): 271–75. http://dx.doi.org/10.4028/www.scientific.net/amr.911.271.

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This paper presents the defect distribution and yield analysis on silicon wafer. The generation and recombination lifetime were the key parameters and obtained from the currentvoltage and the capacitancevoltage of diode characteristics for forward bias. Then 3D contour maps were plotted as defect distribution and can be analyzed for the whole wafer which is useful for the yield analysis of the defects that were caused from fabrication process.

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Astakhov, O., V. Smirnov, R. Carius, B. E. Pieters, Yu Petrusenko, V. Borysenko e F. Finger. "Dependence of open circuit voltage in a-Si:H and μc-Si:H solar cells on defect density in absorber layer varied by 2 MeV electron bombardment". Canadian Journal of Physics 92, n. 7/8 (luglio 2014): 905–8. http://dx.doi.org/10.1139/cjp-2013-0610.

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Theoretically predicted values of the open circuit voltage (VOC) for a-Si:H or μc-Si:H based solar cells are substantially higher than the values achieved in of state-of-the-art devices. Fundamentally, open circuit voltage is determined by generation-recombination kinetics, where recombination is often controlled by the defect density in the absorber layer of a solar cell. The latter aspect is the focus of the paper. The relation between the VOC and the bulk recombination in the absorber layer is addressed in experiment by varying the defect density. The absorber layer defect density (spin density, NS, monitored with ESR) in a-Si:H and μc-Si:H solar cells was varied over two orders of magnitude using a 2 MeV electron bombardment and successive stepwise annealing. The results of the electron bombardment experiment are analyzed with respect to the illumination intensity dependency of the VOC, measured for the same set of a-Si:H and μc-Si:H solar cells. We find that the VOC of a-Si:H solar cells is not limited by defects in the bulk of the absorber layer, even at relatively high defect density up to 3–5 × 1016 cm−3 and, therefore, other limiting mechanisms have to be identified to improve voltage in these devices. In contrast, μc-Si:H solar cells show nearly classical VOC–NS relation. The bulk defect density in μc-Si:H absorber layer is thus likely the key limiting factor for VOC in these devices at present status of material quality (NS of 3–7 × 1015 cm−3). Further optimization of μc-Si:H in terms of bulk defect density is highly relevant for VOC improvement in solar cells.

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Holzäpfel, E., F. Phillipp e M. Wilkens. "On the interpretation of dislocation-loop growth during in-situ high-voltage Electron Microscopy". Proceedings, annual meeting, Electron Microscopy Society of America 48, n. 4 (agosto 1990): 532–33. http://dx.doi.org/10.1017/s042482010017579x.

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During in-situ radiation damage experiments aiming on the investigation of vacancy-migration properties interstitial-type dislocation loops are used as probes monitoring the development of the point defect concentrations. The temperature dependence of the loop-growth rate v is analyzed in terms of reaction-rate theory yielding information on the vacancy migration enthalpy. The relation between v and the point-defect production rate P provides a critical test of such a treatment since it is sensitive to the defect reactions which are dominant. If mutual recombination of vacancies and interstitials is the dominant reaction, vαP0.5 holds. If, however, annihilation of the defects at unsaturable sinks determines the concentrations, a linear relationship vαP is expected.Detailed studies in pure bcc-metals yielded vαPx with 0.7≾×≾1.0 showing that besides recombination of vacancies and interstitials annihilation at sinks plays an important role in the concentration development which has properly to be incorporated into the rate equations.

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26

Seibt, Michael, Philipp Saring, Philipp Hahne, Linda Stolze, M. A. Falkenberg, Carsten Rudolf, Doaa Abdelbarey e Henning Schuhmann. "Transmission Electron Microscopy Investigations of Metal-Impurity-Related Defects in Crystalline Silicon". Solid State Phenomena 178-179 (agosto 2011): 275–84. http://dx.doi.org/10.4028/www.scientific.net/ssp.178-179.275.

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This contribution summarizes recent efforts to apply transmission electron microscopy (TEM) techniques to recombination-active extended defects present in a low density. In order to locate individual defects, electron beam induced current (EBIC) is applied in situ in a focused ion beam (FIB) machine combined with a scanning electron microscope. Using this approach defect densities down to about 10cm-2 are accessible while a target accuracy of better than 50nm is achieved. First applications described here include metal impurity related defects in multicrystalline silicon, recombination and charge collection at NiSi2 platelets, internal gettering of copper by NiSi2 precipitates and site-determination of copper atoms in NiSi2.

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27

Pezoldt, Jörg, e Andrei Alexandrovich Kalnin. "Defects and Polytype Instabilities". Materials Science Forum 924 (giugno 2018): 147–50. http://dx.doi.org/10.4028/www.scientific.net/msf.924.147.

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A model based on the generation and recombination of defect was developed to describe the stability of stacking faults and basal plane dislocation loops in crystals with layered polytype structures. The stability of the defects configuration was analysed for stacking faults surrounded by Shockley and Frank partial dislocation as well as Shockley dislocation dipoles with long range elastic fields. This approach allows the qualitative prediction of defect subsystems in polytype structure in external fields.

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28

Chung, Gil Yong, Mark J. Loboda, Mike F. MacMillan, Jian Wei Wan e Darren M. Hansen. "Carrier Lifetime Analysis by Microwave Photoconductive Decay (μ-PCD) for 4H SiC Epitaxial Wafers". Materials Science Forum 556-557 (settembre 2007): 323–26. http://dx.doi.org/10.4028/www.scientific.net/msf.556-557.323.

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Excess carrier lifetimes in 4H SiC epitaxial wafers were characterized by microwave photoconductive decay (o/PCD). The measured decay compromised of surface and bulk recombination curves have fast and slow components. Measured lifetimes are not changed with various surface passivation techniques. High resolution lifetime maps show good correlation with stress birefringence images and lower lifetime around extended material defects like grainboundaries, defect clusters, edge defects and polytype switching bands. Chlorosilane based CVD epiwafers show higher bulk lifetime values than standard silane based CVD materials due to less bulk lifetime defect density.

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29

Tan, Shaun, Tianyi Huang e Yang Yang. "Defect passivation of perovskites in high efficiency solar cells". Journal of Physics: Energy 3, n. 4 (1 ottobre 2021): 042003. http://dx.doi.org/10.1088/2515-7655/ac2e13.

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Abstract Metal halide perovskite solar cells (PSCs) have enormous potential as the next-generation photovoltaic technology. Being solution-processed at relatively low temperatures, it is inevitable that crystallographic defects are formed in abundance during fabrication. Such defects may cause undesirable energy losses by non-radiative recombination to limit the performance of PSCs. More importantly, it has become apparent that defect activity is fundamentally responsible for the operational instability issues hindering the commercialization readiness of PSCs. It is therefore necessary to develop strategies to minimize defect formation and to passivate formed defects. Here, we discuss recent advances on such defect mitigation and passivation strategies. We especially emphasize on methodologies that are incorporated into state-of-the-art PSCs that have demonstrated world record efficiencies and long-term stability.

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30

Weber, William J., Fei Gao, Ram Devanathan, Weilin Jiang e Y. Zhang. "Defects and Ion-Solid Interactions in Silicon Carbide". Materials Science Forum 475-479 (gennaio 2005): 1345–50. http://dx.doi.org/10.4028/www.scientific.net/msf.475-479.1345.

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Atomic-level simulations are used to determine defect production, cascade-overlap effects, and defect migration energies in SiC. Energetic C and Si collision cascades primarily produce single interstitials, mono-vacancies, antisite defects, and small defect clusters, while amorphous clusters are produced within 25% of Au cascades. Cascade overlap results in defect stimulated cluster growth that drives the amorphization process. The good agreement of disordering behavior and changes in volume and elastic modulus obtained computationally and experimentally provides atomic-level interpretation of experimentally observed features. Simulations indicate that close-pair recombination activation energies range from 0.24 to 0.38 eV, and long-range migration energies for interstitials and vacancies are determined.

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31

Yassievich, I. N., V. N. Abakumov e A. A. Pakhomov. "Recombination-Induced Defect Heating and Related Phenomena". Materials Science Forum 83-87 (gennaio 1992): 511–16. http://dx.doi.org/10.4028/www.scientific.net/msf.83-87.511.

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32

Law, M. E. "Parameters for point-defect diffusion and recombination". IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems 10, n. 9 (1991): 1125–31. http://dx.doi.org/10.1109/43.85758.

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33

Verner, I. V., e J. W. Corbett. "Instabilities and nonlinearities in defect recombination processes". Radiation Effects and Defects in Solids 112, n. 3 (gennaio 1990): 85–87. http://dx.doi.org/10.1080/10420159008213034.

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34

Shu, Yinan, B. Scott Fales e Benjamin G. Levine. "Defect-Induced Conical Intersections Promote Nonradiative Recombination". Nano Letters 15, n. 9 (24 agosto 2015): 6247–53. http://dx.doi.org/10.1021/acs.nanolett.5b02848.

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35

Shimoi, Hitoshi, Yuta Hanazumi, Natsuki Kawamura, Miwa Yamada, Shohei Shimizu, Taro Suzuki, Daisuke Watanabe e Takeshi Akao. "Meiotic chromosomal recombination defect in sake yeasts". Journal of Bioscience and Bioengineering 127, n. 2 (febbraio 2019): 190–96. http://dx.doi.org/10.1016/j.jbiosc.2018.07.027.

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36

Yassievich, I. N. "Recombination-induced defect heating and related phenomena". Semiconductor Science and Technology 9, n. 8 (1 agosto 1994): 1433–53. http://dx.doi.org/10.1088/0268-1242/9/8/001.

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37

SHIMOI, Hitoshi. "Meiotic Chromosomal Recombination Defect in Sake Yeast". JOURNAL OF THE BREWING SOCIETY OF JAPAN 116, n. 7 (2021): 464–72. http://dx.doi.org/10.6013/jbrewsocjapan.116.464.

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38

Sakowski, Konrad, Pawel Strak, Pawel Kempisty, Jacek Piechota, Izabella Grzegory, Piotr Perlin, Eva Monroy, Agata Kaminska e Stanislaw Krukowski. "Coulomb Contribution to Shockley–Read–Hall Recombination". Materials 17, n. 18 (18 settembre 2024): 4581. http://dx.doi.org/10.3390/ma17184581.

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A nonradiative recombination channel is proposed, which does not vanish at low temperatures. Defect-mediated nonradiative recombination, known as Shockley–Read–Hall (SRH) recombination, is reformulated to accommodate Coulomb attraction between the charged deep defect and the approaching free carrier. It is demonstrated that this effect may cause a considerable increase in the carrier velocity approaching the recombination center. The effect considerably increases the carrier capture rates. It is demonstrated that, in a typical semiconductor device or semiconductor medium, the SRH recombination rate at low temperatures is much higher and cannot be neglected. This effect renders invalid the standard procedure of estimating the radiative recombination rate by measuring the light output in cryogenic temperatures, as a significant nonradiative recombination channel is still present. We also show that SRH is more effective in the case of low-doped semiconductors, as effective screening by mobile carrier density could reduce the effect.

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39

Poteete, Anthony R., e Anita C. Fenton. "Genetic Requirements of Phage λ Red-Mediated Gene Replacement in Escherichia coli K-12". Journal of Bacteriology 182, n. 8 (15 aprile 2000): 2336–40. http://dx.doi.org/10.1128/jb.182.8.2336-2340.2000.

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ABSTRACT Recombination between short linear double-stranded DNA molecules and Escherichia coli chromosomes bearing thered genes of bacteriophage λ in place ofrecBCD was tested in strains bearing mutations in genes known to affect recombination in other cellular pathways. The linear DNA was a 4-kb fragment containing the cat gene, with flanking lac sequences, released from an infecting phage chromosome by restriction enzyme cleavage in the cell; formation of Lac− chloramphenicol-resistant bacterial progeny was measured. Recombinant formation was found to be reduced inruvAB and recQ strains. In this genetic background, mutations in recF, recO, andrecR had large effects on both cell viability and on recombination. In these cases, deletion of the sulA gene improved viability and strain stability, without improving recombination ability. Expression of a gene(s) from the ninregion of phage λ partially complemented both the viability and recombination defects of the recF, recO, andrecR mutants and the recombination defect ofruvC but not of ruvAB or recQmutants.

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40

Smith, J., e R. Rothstein. "A mutation in the gene encoding the Saccharomyces cerevisiae single-stranded DNA-binding protein Rfa1 stimulates a RAD52-independent pathway for direct-repeat recombination." Molecular and Cellular Biology 15, n. 3 (marzo 1995): 1632–41. http://dx.doi.org/10.1128/mcb.15.3.1632.

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In the yeast Saccharomyces cerevisiae, recombination between direct repeats is synergistically reduced in rad1 rad52 double mutants, suggesting that the two genes define alternate recombination pathways. Using a classical genetic approach, we searched for suppressors of the recombination defect in the double mutant. One mutation that restores wild-type levels of recombination was isolated. Cloning by complementation and subsequent physical and genetic analysis revealed that it maps to RAF1. This locus encodes the large subunit of the single-stranded DNA-binding protein complex, RP-A, which is conserved from S. cerevisiae to humans. The rfa1 mutation on its own causes a 15-fold increase in direct-repeat recombination. However, unlike most other hyperrecombination mutations, the elevated levels in rfa1 mutants occur independently of RAD52 function. Additionally, rfa1 mutant strains grow slowly, are UV sensitive, and exhibit decreased levels of heteroallelic recombination. DNA sequence analysis of rfa1 revealed a missense mutation that alters a conserved residue of the protein (aspartic acid 228 to tyrosine [D228Y]). Biochemical analysis suggests that this defect results in decreased levels of RP-A in mutant strains. Overexpression of the mutant subunit completely suppresses the UV sensitivity and partially suppresses the recombination phenotype. We propose that the defective complex fails to interact properly with components of the repair, replication, and recombination machinery. Further, this may permit the bypass of the recombination defect of rad1 rad52 mutants by activating an alternative single-stranded DNA degradation pathway.

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41

GRÜNEIS, FERDINAND. "1/f NOISE IN EXTRINSIC SEMICONDUCTOR MATERIALS INTERPRETED AS MODULATED GENERATION-RECOMBINATION NOISE". Fluctuation and Noise Letters 09, n. 02 (giugno 2010): 229–43. http://dx.doi.org/10.1142/s0219477510000137.

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We investigate fixed dopants in the presence of mobile point defects. A defect entering the first Bohr radius RB of a dopant will modulate the generation-recombination (g-r) process. The times a defect walks inside and outside of RB are found to be power-law distributed; correspondingly, the modulated g-r process exhibits 1/fb noise. The predicted Hooge coefficient depends on RB, on the normalized fluctuations of charge carriers, the number of lattice sites and on the modulation depth of the g-r process.

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42

Huertas, Pablo, María L. García-Rubio, Ralf E. Wellinger, Rosa Luna e Andrés Aguilera. "An hpr1 Point Mutation That Impairs Transcription and mRNP Biogenesis without Increasing Recombination". Molecular and Cellular Biology 26, n. 20 (14 agosto 2006): 7451–65. http://dx.doi.org/10.1128/mcb.00684-06.

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ABSTRACT THO/TREX, a conserved eukaryotic protein complex, is a key player at the interface between transcription and mRNP metabolism. The lack of a functional THO complex impairs transcription, leads to transcription-dependent hyperrecombination, causes mRNA export defects and fast mRNA decay, and retards replication fork progression in a transcription-dependent manner. To get more insight into the interconnection between mRNP biogenesis and genomic instability, we searched for HPR1 mutations that differentially affect gene expression and recombination. We isolated mutants that were barely affected in gene expression but exhibited a hyperrecombination phenotype. In addition, we isolated a mutant, hpr1-101, with a strong defect in transcription, as observed for lacZ, and a general defect in mRNA export that did not display a relevant hyperrecombination phenotype. In THO single-null mutants, but not in the hpr1 point mutants studied, THO and its subunits were unstable. Interestingly, in contrast to hyperrecombinant null mutants, hpr1-101 did not cause retardation of replication fork progression. Transcription and mRNP biogenesis can therefore be impaired by THO/TREX dysfunction without increasing recombination, suggesting that it is possible to separate the mechanism(s) responsible for mRNA biogenesis defects from the further step of triggering transcription-dependent recombination.

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43

Meftah, Afek, Noureddine Sengouga e Amjad Meftah. "Prediction of the performance degradation of GaAs solar cells by electron irradiation". Journal of Renewable Energies 11, n. 4 (31 dicembre 2008): 603–10. http://dx.doi.org/10.54966/jreen.v11i4.110.

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Solar cells exposed to irradiation undergo severe degradation in their performance due to induced structural defects. To predict this effect, the current-voltage characteristics under AM0 illumination for a constant dose of electron irradiation are numerically calculated. From these characteristics the solar cell output parameters: the short circuit current density Jsc, the open circuit voltage Voc, the fill factor FF and the conversion efficiency are extracted. The irradiation induced defects introduce in the energy gap either recombination centres or traps. The irradiation induced degradation is widely attributed to the first type of defects. We have adopted a strategy to find out which defects are responsible for the degradation. This consists of simulating the effect of each defect separately on the output parameters. The simulation results show that traps are mainly responsible for the degradation of Jsc while recombination centres are responsible the degradation of Voc. The other parameters (FF and ) are degraded by the combination of the traps and recombination centres.

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44

Zahradka, Davor, Ksenija Zahradka, Mirjana Petranović, Damir Đermić e Krunoslav Brčić-Kostić. "The RuvABC Resolvase Is Indispensable for Recombinational Repair in sbcB15 Mutants of Escherichia coli". Journal of Bacteriology 184, n. 15 (1 agosto 2002): 4141–47. http://dx.doi.org/10.1128/jb.184.15.4141-4147.2002.

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ABSTRACT The RuvABC proteins of Escherichia coli play an important role in the processing of Holliday junctions during homologous recombination and recombinational repair. Mutations in the ruv genes have a moderate effect on recombination and repair in wild-type strains but confer pronounced recombination deficiency and extreme sensitivity to DNA-damaging agents in a recBC sbcBC background. Genetic analysis presented in this work revealed that the ΔruvABC mutation causes an identical DNA repair defect in UV-irradiated recBC sbcBC, sbcBC, and sbcB strains, indicating that the sbcB mutation alone is responsible for the extreme UV sensitivity of recBC sbcBC ruv derivatives. In experiments with gamma irradiation and in conjugational crosses, however, sbcBC ΔruvABC and sbcB ΔruvABC mutants displayed higher recombination proficiency than the recBC sbcBC ΔruvABC strain. The frequency of conjugational recombination observed with the sbcB ΔruvABC strain was quite similar to that of the ΔruvABC single mutant, indicating that the sbcB mutation does not increase the requirement for RuvABC in a recombinational process starting from preexisting DNA ends. The differences between the results obtained in three experimental systems used suggest that in UV-irradiated cells, the RuvABC complex might act in an early stage of recombinational repair. The results of this work are discussed in the context of recent recombination models which propose the participation of RuvABC proteins in the processing of Holliday junctions made from stalled replication forks. We suggest that the mutant SbcB protein stabilizes these junctions and makes their processing highly dependent on RuvABC resolvase.

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45

Das, Basita, Zhifa Liu, Irene Aguilera, Uwe Rau e Thomas Kirchartz. "Defect tolerant device geometries for lead-halide perovskites". Materials Advances 2, n. 11 (2021): 3655–70. http://dx.doi.org/10.1039/d0ma00902d.

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46

Bailis, A. M., e R. Rothstein. "A defect in mismatch repair in Saccharomyces cerevisiae stimulates ectopic recombination between homeologous genes by an excision repair dependent process." Genetics 126, n. 3 (1 novembre 1990): 535–47. http://dx.doi.org/10.1093/genetics/126.3.535.

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Abstract Null mutations in three recombination and DNA repair genes were studied to determine their effects on mitotic recombination between the duplicate AdoMet (S-adenosylmethionine) synthetase genes (SAM1 and SAM2) in Saccharomyces cerevisiae. SAM1 and SAM2, located on chromosomes XII and IV, respectively, encode functionally equivalent although differentially regulated AdoMet synthetases. These similar but not identical (homeologous) genes are 83% homologous at the nucleotide level and this identity is limited solely to the coding regions of the genes. Single frameshift mutations were introduced into the 5' end of SAM1 and the 3' end of SAM2 by restriction site ablation. The sequences surrounding these mutations differ significantly in their degree of homology to the corresponding area of the other gene. Mitotic ectopic recombination between the mutant sam genes occurs at a rate of 8.4 x 10(-9) in a wild-type genetic background. Gene conversion of the marker within the region of greater sequence homology occurs 20-fold more frequently than conversion of the marker within the region of relative sequence diversity. The relative orientation of the two genes prevents the recovery of translocations. Mitotic recombination between the sam genes is completely dependent on the DNA repair and recombination gene RAD52. A mutation in PMS1, a mismatch repair gene, causes a 4.5-fold increase in the rate of ectopic recombination. RAD1, an excision repair gene, is required to observe this increased rate of ectopic conversion. In addition, RAD1 is involved in modulating the pattern of coconversion during recombination between the homeologous sam genes. These results suggest that interactions between mismatch repair, excision repair and recombinational repair functions are involved in determining the ectopic gene conversion frequency between the sam genes.

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47

Mahadik, Nadeemullah A., Robert E. Stahlbush, Syed B. Qadri, Orest J. Glembocki, Dimitri A. Alexson, Rachael L. Myers-Ward, Joseph L. Tedesco, Charles R. Eddy e D. Kurt Gaskill. "Structure of Inclusions in 4° Offcut 4H-SiC Epitaxy". Materials Science Forum 645-648 (aprile 2010): 315–18. http://dx.doi.org/10.4028/www.scientific.net/msf.645-648.315.

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The structure of various inclusions in SiC epitaxial layers grown on 4o offcut substrates was investigated using three advanced techniques. Using micro-Raman spectroscopy, the observed inclusions exhibited a complex structure having either different SiC polytypes like 3C or 6H or they were misoriented 4H-SiC inclusions. The UVPL images showed dislocations and other extended defects around the inclusion-related defects, and strain fields were observed in the x-ray topographs near the defect sites. Spectral UVPL imaging shows features with varying luminescence inside the inclusion related defects which propagate and may cause deformation in the crystalline structure and lead to non-radiative recombination centers within the defect.

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48

Fang, Yu, Jianping Wang, Fangyuan Shi, Zhengguo Xiao, Xingzhi Wu, Junyi Yang, Yongqiang Chen, Quanying Wu e Yinglin Song. "Native defect-related broadband ultrafast photocarrier dynamics in n-type β-Ga₂O₃". Applied Physics Letters 121, n. 11 (12 settembre 2022): 112103. http://dx.doi.org/10.1063/5.0100190.

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We report two-photon excited ultrafast carrier trapping and recombination in n-type β-Ga2O3 crystals by using femtosecond transient absorption spectroscopy. The broadband absorption spectra arising from the defect are polarization dependent, especially, two absorption peaks can be observed by subtracting the absorption transients under two probe polarizations. We attribute these observed defect-related absorption features to optical transitions from the valence band to different charge states of a native defect (such as gallium vacancies). A model for carrier capture by multilevel of a single defect is proposed to interpret the data, wherein holes are captured more efficiently than electrons by the defects, and the absorption cross sections for the defects are at least ten times larger than that for free carriers. Our results reveal the potential applications of β-Ga2O3 in ultrafast and broadband optoelectronic devices.

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49

Tian, Ming, Reiko Shinkura, Nobuhiko Shinkura e Frederick W. Alt. "Growth Retardation, Early Death, and DNA Repair Defects in Mice Deficient for the Nucleotide Excision Repair Enzyme XPF". Molecular and Cellular Biology 24, n. 3 (1 febbraio 2004): 1200–1205. http://dx.doi.org/10.1128/mcb.24.3.1200-1205.2004.

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ABSTRACT Xeroderma pigmentosum (XP) is a human genetic disease which is caused by defects in nucleotide excision repair. Since this repair pathway is responsible for removing UV irradiation-induced damage to DNA, XP patients are hypersensitive to sunlight and are prone to develop skin cancer. Based on the underlying genetic defect, the disease can be divided into the seven complementation groups XPA through XPG. XPF, in association with ERCC1, constitutes a structure-specific endonuclease that makes an incision 5′ to the photodamage. XPF-ERCC1 has also been implicated in both removal of interstrand DNA cross-links and homology-mediated recombination and in immunoglobulin class switch recombination (CSR). To study the function of XPF in vivo, we inactivated the XPF gene in mice. XPF-deficient mice showed a severe postnatal growth defect and died approximately 3 weeks after birth. Histological examination revealed that the liver of mutant animals contained abnormal cells with enlarged nuclei. Furthermore, embryonic fibroblasts defective in XPF are hypersensitive to UV irradiation and mitomycin C treatment. No defect in CSR was detected, suggesting that the nuclease is dispensable for this recombination process. These phenotypes are identical to those exhibited by the ERCC1-deficient mice, consistent with the functional association of the two proteins. The complex phenotype suggests that XPF-ERCC1 is involved in multiple DNA repair processes.

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50

Webster, P. T., R. A. Carrasco, A. T. Newell, J. V. Logan, P. C. Grant, D. Maestas e C. P. Morath. "Utility of Shockley–Read–Hall analysis to extract defect properties from semiconductor minority carrier lifetime data". Journal of Applied Physics 133, n. 12 (28 marzo 2023): 125704. http://dx.doi.org/10.1063/5.0147482.

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The semiconductor minority carrier lifetime contains information about several important material properties, including Shockley–Read–Hall defect levels/concentrations and radiative/Auger recombination rates, and the complex relationships between these parameters produce a non-trivial temperature-dependence of the measured lifetime. It is tempting to fit temperature-dependent lifetime data to extract the properties of the Shockley–Read–Hall recombination centers; however, without a priori knowledge of the distribution of the Shockley–Read–Hall states across the bandgap, this fit problem is under-constrained in most circumstances. Shockley–Read–Hall lifetime data are not well-suited for the extraction of Shockley–Read–Hall defect levels but can be used effectively to extract minority carrier recombination lifetimes. The minority carrier recombination lifetime is observed at temperatures below 100 K in a Si-doped n-type InGaAs/InAsSb superlattice, and deviation from its expected temperature-dependence indicates that the capture cross section of the defect associated with Si-doping has an activation energy of 1.5 meV or a characteristic temperature of 17 K. This lower temperature regime is also preferrable for the analysis of the physics of defect introduction with displacement-damage-generating particle irradiation.

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