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R. Aaij - One of the best experts on this subject based on the ideXlab platform.
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Measurement of the B0s→μ+μ− branching fraction and Effective Lifetime and search for B0→μ+μ− decays
Physical Review Letters, 2017Co-Authors: R. Aaij, L. Beaucourt, Maximilien Chefdeville, Daniel Decamp, Nicolas Déléage, Philippe Ghez, J. F. Marchand, Marie-noelle Minard, Boleslaw Pietrzyk, Stephane T'jampensAbstract:A search for the rare decays B0s→μ+μ− and B0→μ+μ− is performed at the LHCb experiment using data collected in pp collisions corresponding to a total integrated luminosity of 4.4 fb−1. An excess of B0s→μ+μ− decays is observed with a significance of 7.8 standard deviations, representing the first observation of this decay in a single experiment. The branching fraction is measured to be B(B0s→μ+μ−)=(3.0±0.6+0.3−0.2)×10−9, where the first uncertainty is statistical and the second systematic. The first measurement of the B0s→μ+μ− Effective Lifetime, τ(B0s→μ+μ−)=2.04±0.44±0.05 ps, is reported. No significant excess of B0→μ+μ− decays is found and a 95 % confidence level upper limit, B(B0→μ+μ−)
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measurement of the bs0 μ μ branching fraction and Effective Lifetime and search for b0 μ μ decays
Physical Review Letters, 2017Co-Authors: R. Aaij, L. Beaucourt, Maximilien Chefdeville, Daniel Decamp, Nicolas Déléage, Philippe Ghez, J. F. Marchand, Marie-noelle Minard, Boleslaw Pietrzyk, S TjampensAbstract:A search for the rare decays B0s→μ+μ− and B0→μ+μ− is performed at the LHCb experiment using data collected in pp collisions corresponding to a total integrated luminosity of 4.4 fb−1. An excess of B0s→μ+μ− decays is observed with a significance of 7.8 standard deviations, representing the first observation of this decay in a single experiment. The branching fraction is measured to be B(B0s→μ+μ−)=(3.0±0.6+0.3−0.2)×10−9, where the first uncertainty is statistical and the second systematic. The first measurement of the B0s→μ+μ− Effective Lifetime, τ(B0s→μ+μ−)=2.04±0.44±0.05 ps, is reported. No significant excess of B0→μ+μ− decays is found and a 95 % confidence level upper limit, B(B0→μ+μ−)<3.4×10−10, is determined. All results are in agreement with the Standard Model expectations.
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measurement of the bs0 j ψη Lifetime
Physics Letters B, 2016Co-Authors: R. Aaij, L. Beaucourt, J. F. Marchand, M Chefdeville, D Decamp, N Deleage, P Ghez, J P Lees, M N Minard, B PietrzykAbstract:Using a data set corresponding to an integrated luminosity of 3fb−1, collected by the LHCb experiment in pp collisions at centre-of-mass energies of 7 and 8 TeV, the Effective Lifetime in the B0s→J/ψη decay mode, τeff, is measured to be τeff=1.479±0.034 (stat)±0.011 (syst) ps. Assuming CP conservation, τeff corresponds to the Lifetime of the light B0s mass eigenstate. This is the first measurement of the Effective Lifetime in this decay mode.
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Measurement of the B0s→J/ψη Lifetime
Physics Letters B, 2016Co-Authors: R. Aaij, L. Beaucourt, J. F. Marchand, M Chefdeville, D Decamp, N Deleage, P Ghez, J P Lees, M N Minard, B PietrzykAbstract:Using a data set corresponding to an integrated luminosity of 3fb−1, collected by the LHCb experiment in pp collisions at centre-of-mass energies of 7 and 8 TeV, the Effective Lifetime in the B0s→J/ψη decay mode, τeff, is measured to be τeff=1.479±0.034 (stat)±0.011 (syst) ps. Assuming CP conservation, τeff corresponds to the Lifetime of the light B0s mass eigenstate. This is the first measurement of the Effective Lifetime in this decay mode.
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Effective Lifetime measurements in the b s 0 k k b 0 k pi and b s 0 pi k decays
Physics Letters B, 2014Co-Authors: R. Aaij, B Adeva, M Adinolfi, A Affolder, Z Ajaltouni, J Albrecht, F Alessio, Michael Alexander, S. AliAbstract:Measurements of the Effective Lifetimes in the B-s(0) -> K+K-, B-0 -> K+pi(-) and B-s(0) -> pi K-+(-) decays are presented using 1.0 fb(-1)of pp collision data collected at a centre-of-mass energy of 7 TeV by the LHCb experiment. The analysis uses a data-driven approach to correct for the decay time acceptance. The measured Effective Lifetimes are tau(Bs0 -> K+K-) = 1.407 +/- 0.016 (stat) +/- 0.007 (syst) ps, tau(Bs0 -> K+pi-) = 1.524 +/- 0.011 (stat) +/- 0.004 (syst) ps, tau(Bs0 ->pi+K-) = 1.60 +/- 0.06 (stat) +/- 0.01 (syst) ps. This is the most precise determination to date of the Effective Lifetime in the B-s(0) -> K+K- decay and provides constraints on contributions from physics beyond the Standard Model to the B-s(0) mixing phase and the width difference Delta Gamma(s). (C) 2014 The Authors. Published by Elsevier B.V.
Ziv Hameiri - One of the best experts on this subject based on the ideXlab platform.
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numerical simulations of two photon absorption time resolved photoluminescence to extract the bulk Lifetime of semiconductors under varying surface recombination velocities
Journal of Applied Physics, 2019Co-Authors: Robert Lee Chin, Thorsten Trupke, Michael E Pollard, Ziv HameiriAbstract:We investigate the limitations of two-photon absorption time-resolved photoluminescence to measure the low-injection bulk Lifetime of different semiconductor materials under varying surface recombination. The excitation source is assumed to be a sub-bandgap pulsed laser and the localized absorption and carrier generation was modeled using a focused TEM00 Gaussian beam under the assumption of diffraction-limited performance. The subsequent carrier kinetics were simulated by applying the finite-difference time-domain method to the continuity equation. Three typical semiconductor materials were modeled: direct bandgap low-mobility material (such as CZTS), direct bandgap high mobility (such as GaAs), and indirect bandgap high mobility (such as float-zone silicon). The extracted Effective Lifetime as a function of surface recombination velocity was compared to the bulk Lifetime and the Effective Lifetime calculated using an analytical 1D approximation. For the direct bandgap materials, focusing inside the material yields an Effective Lifetime within a few percent of the bulk Lifetime, regardless of the surface recombination velocity, while for excitation close to the surface it is up to 30% lower than the bulk Lifetime at high surface recombination velocities (>104 cm/s). For the indirect bandgap material, the Effective Lifetime is dominated by the surface, making the bulk Lifetime inaccessible, even at surface recombination velocities of 100 cm/s. Finally, we use the 1D approximation to find under what conditions the bulk Lifetime can be extracted by this method and determine that both the bulk diffusion length and the product of the bulk Lifetime and surface recombination velocity must be much less than twice the device thickness.We investigate the limitations of two-photon absorption time-resolved photoluminescence to measure the low-injection bulk Lifetime of different semiconductor materials under varying surface recombination. The excitation source is assumed to be a sub-bandgap pulsed laser and the localized absorption and carrier generation was modeled using a focused TEM00 Gaussian beam under the assumption of diffraction-limited performance. The subsequent carrier kinetics were simulated by applying the finite-difference time-domain method to the continuity equation. Three typical semiconductor materials were modeled: direct bandgap low-mobility material (such as CZTS), direct bandgap high mobility (such as GaAs), and indirect bandgap high mobility (such as float-zone silicon). The extracted Effective Lifetime as a function of surface recombination velocity was compared to the bulk Lifetime and the Effective Lifetime calculated using an analytical 1D approximation. For the direct bandgap materials, focusing inside the mate...
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extracting metal contact recombination parameters from Effective Lifetime data
IEEE Journal of Photovoltaics, 2018Co-Authors: Robert Dumbrell, Mattias K Juhl, Thorsten Trupke, Ziv HameiriAbstract:The surface recombination at metallized surfaces of a solar cell is of significant interest for cell process development, considering the limiting effect such recombination has on cell efficiency. This recombination is difficult to measure accurately, because the enhanced recombination at the metal contacts causes an inhomogeneous minority carrier profile, which limits the viability of conventional photoconductance-based recombination measurements. In this study, a photoluminescence-based system is used to measure the injection-dependent Effective Lifetime of full area metallized samples. Several techniques to extract surface recombination parameters from these data are compared. A simulation-based approach is shown to be superior to the simplified analyses that are more commonly applied to data of this type, in the case where the depth profile of the minority carrier density is nonuniform.
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the impact of surface damage region and edge recombination on the Effective Lifetime of silicon wafers at low illumination conditions
Journal of Applied Physics, 2015Co-Authors: Ziv HameiriAbstract:The Effective minority carrier Lifetime of p-type silicon wafers passivated by silicon nitride and of n-type silicon wafers passivated by aluminium oxide often decreases significantly as the excess carrier concentration decreases. Several theories have been postulated to explain this effect. The main ones are asymmetric carrier Lifetimes, high recombination within a surface damage region, and edge recombination. As in some cases, the Effective Lifetime measurements can be fitted quite well by all these effects, it is challenging to determine the main cause for the suppressed performance at low illumination. This is partly due to the fact that no study has yet included a sufficiently large set of wafers and advanced modelling to examine all these theories. The aim of this study is to determine the most likely theory based on a set of undiffused p- and n-type wafers of different sizes, passivated with both silicon nitride and aluminium oxide. Quasi-steady-state photoluminescence measurements were used in order to investigate Effective Lifetime at very low carrier densities, without artifact effects that commonly limit photoconductance-based measurements. Advanced modelling using Sentaurus was used to investigate the impact of different parameters—such as the fixed charge within the dielectric—on the recombination at the edge and within the surface damage region. These models were then used to simulate the measurement results. It is shown that asymmetrical surface Lifetime cannot explain the observed reduction when the dielectric is highly charged (either positively or negatively). It is also shown that although edge recombination influences the Effective Lifetime at low excess carrier concentration, it alone cannot explain the Effective Lifetime reduction. It is therefore concluded that the presence of a surface damage region is the more likely explanation for the Effective Lifetime decrease of the studied wafers.
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Investigation of low injection effects using the local ideality factor obtained from Effective Lifetime measurements
2014 IEEE 40th Photovoltaic Specialist Conference (PVSC), 2014Co-Authors: Ziv Hameiri, Keith R McintoshAbstract:The Effective minority carrier Lifetime of p-type silicon wafers passivated by silicon nitride and of n-type silicon wafers passivated by aluminum oxide often decreases significantly as the excess carrier concentration decreases. Several theories have been postulated to explain this effect. The main ones are asymmetric carrier Lifetimes, high recombination within a surface damage region, and edge recombination. As in some cases the Effective Lifetime measurements can be fitted quite well by all these effects, it is challenging to determine which of them limits the low injection performance of a specific wafer. This study demonstrates that although these mechanisms affect the Lifetime in ways that are difficult to be distinguished, they have a significantly different influence on the resulting injection-dependent local ideality factor. It is therefore suggested that the injection dependent local ideality factor can be used to distinguish between these mechanisms.
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low injection effects using the local ideality factor obtained from Effective Lifetime measurements
2014Co-Authors: Ziv Hameiri, Keith R McintoshAbstract:The Effective minority carrier Lifetime of p-type silicon wafers passivated by silicon nitride and of n-type silicon wafers passivated by aluminum oxide often decreases significantly as the excess carrier concentration decreases. Several theories have been postulated to explain this effect. The main ones are asymmetric carrier Lifetimes, high recombination within a surface damage region, and edge recombination. As in some cases the Effective Lifetime measurements can be fitted quite well by all these effects, it is challenging to determine which of them limits the low injection performance of a specific wafer. This study demonstrates that although these mechanisms affect the Lifetime in ways that are difficult to be distinguished, they have a significantly different influence on the resulting injection dependent local ideality factor. It is therefore suggested that the injection dependent local ideality factor can be used to distinguish between these mechanisms.
Miro Zeman - One of the best experts on this subject based on the ideXlab platform.
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understanding the thickness dependent Effective Lifetime of crystalline silicon passivated with a thin layer of intrinsic hydrogenated amorphous silicon using a nanometer accurate wet etching method
Journal of Applied Physics, 2016Co-Authors: Dimitrios Deligiannis, Vasileios Marioleas, Ravi Vasudevan, Cassan C G Visser, Rene A C M M Van Swaaij, Miro ZemanAbstract:This work studies the dependency of the Effective Lifetime on the a-Si:H layer thickness of c-Si substrates passivated with intrinsic a-Si:H. This is experimentally investigated by using a soft wet-etching method that enables accurate control of the a-Si:H layer thickness. In this way, variations in the Effective Lifetime down to thicknesses of a few nanometers are studied, while excluding effects originating from the deposition conditions of a-Si:H when samples of different thicknesses are fabricated. For thin passivation layers, results show a strong thickness dependency of the Effective Lifetime, which is mainly influenced by the recombination at the external a-Si:H surfaces. For thicker passivation layers, the Effective Lifetime is predominantly determined by the bulk a-Si:H and/or c-Si defect density. During the etching of the a-Si:H passivation layers, a gradient in the Cody gap for our samples is observed. This gradient is accompanied by a stronger decrease in the Effective Lifetime and is attribut...
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understanding the thickness dependent Effective Lifetime of crystalline silicon passivated with a thin layer of intrinsic hydrogenated amorphous silicon using a nanometer accurate wet etching method
Journal of Applied Physics, 2016Co-Authors: Dimitrios Deligiannis, Vasileios Marioleas, Ravi Vasudevan, Cassan C G Visser, Rene A C M M Van Swaaij, Miro ZemanAbstract:This work studies the dependency of the Effective Lifetime on the a-Si:H layer thickness of c-Si substrates passivated with intrinsic a-Si:H. This is experimentally investigated by using a soft wet-etching method that enables accurate control of the a-Si:H layer thickness. In this way, variations in the Effective Lifetime down to thicknesses of a few nanometers are studied, while excluding effects originating from the deposition conditions of a-Si:H when samples of different thicknesses are fabricated. For thin passivation layers, results show a strong thickness dependency of the Effective Lifetime, which is mainly influenced by the recombination at the external a-Si:H surfaces. For thicker passivation layers, the Effective Lifetime is predominantly determined by the bulk a-Si:H and/or c-Si defect density. During the etching of the a-Si:H passivation layers, a gradient in the Cody gap for our samples is observed. This gradient is accompanied by a stronger decrease in the Effective Lifetime and is attributed to a decrease in the a-Si:H band gap and valence band offset. The observed changes in Lifetime with a-Si:H layer thickness are supported with AFORS-HET simulations. When a gradient in the a-Si:H passivation layer band gap is used, simulations can reproduce the experimental results.
Ramon Alcubilla - One of the best experts on this subject based on the ideXlab platform.
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characterization of a si h c si interfaces by Effective Lifetime measurements
Journal of Applied Physics, 2005Co-Authors: M. Garín, Uwe Rau, W. Brendle, Isidro Martín, Ramon AlcubillaAbstract:This article studies theoretically and experimentally the recombination at the amorphous/crystalline silicon interface of a heterojunction with intrinsic thin layer (HIT) structure without metallization. We propose a physical model to calculate the interface recombination rate under illumination. This model calculates the Effective Lifetime τeff as a function of the average excess minority carrier concentration ⟨Δn⟩. In order to test the model, we prepared a set of HIT structures. The dependence of τeff vs ⟨Δn⟩ of the samples is measured using the quasi-steady-state photoconductance technique. By fitting our model to the experimental data, we determine the a-Si:H∕c-Si interface parameters and the doping density of the amorphous layer.
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Characterization of a-Si:H∕c-Si interfaces by Effective-Lifetime measurements
Journal of Applied Physics, 2005Co-Authors: M. Garín, Uwe Rau, W. Brendle, Isidro Martín, Ramon AlcubillaAbstract:This article studies theoretically and experimentally the recombination at the amorphous/crystalline silicon interface of a heterojunction with intrinsic thin layer (HIT) structure without metallization. We propose a physical model to calculate the interface recombination rate under illumination. This model calculates the Effective Lifetime τeff as a function of the average excess minority carrier concentration ⟨Δn⟩. In order to test the model, we prepared a set of HIT structures. The dependence of τeff vs ⟨Δn⟩ of the samples is measured using the quasi-steady-state photoconductance technique. By fitting our model to the experimental data, we determine the a-Si:H∕c-Si interface parameters and the doping density of the amorphous layer.
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Effective Lifetime measurements on phosphorus emitters prepared with planar diffusion sources
Conference on Electron Devices 2005 Spanish, 2005Co-Authors: Pedro A. Ortega, Michael Vetter, I. Torres, Sandra Bermejo, Ramon AlcubillaAbstract:In this work we present a study of phosphorus doped emitters using solid diffusion sources. This doping technique has a special interest in high efficiency solar cell fabrication because it can reach good uniformity and repeatability between samples, allowing uniform low doping emitter profiles (sheet resistance Rsh/100Omegasq). Pre-deposition in the temperature range from 815degC to 900degC yields emitter sheet resistance from 30 to 900 Omega/sq with a in-wafer deviation of about 6% on 4" wafers. We determine the reverse saturation current density, Joe, of our emitters by measuring the injection level dependence of Effective Lifetime using the quasi steady-state photoconductance (QSS-PC) method. Joe in phosphorus glass passivated emitters after the pre-deposition step is in the range of 160 to 400 fA/cm2. From data fitting of dependence of Joe with sheet resistance using PC-ID, the empiric fundamental surface recombination velocity is determined to be So= 175 cm/s for the phosphorus glass passivated emitter surface
P. Robbe - One of the best experts on this subject based on the ideXlab platform.
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Measurement of the $\bar{B}_s^0\to D_s^-D_s^+$ and $\bar{B}_s^0\to D^-D_s^+$ Effective Lifetimes
Physical Review Letters, 2014Co-Authors: R. Aaij, S. Barsuk, O. Callot, J. Lefrançois, F. Machefert, A. Martin Sanchez, M. Nicol, Y. Amhis, O. Kochebina, P. RobbeAbstract:The first measurement of the Effective Lifetime of the $\bar{B}_s^0$ meson in the decay $\bar{B}_s^0\to D_s^-D_s^+$ is reported using a proton-proton collision dataset, corresponding to an integrated luminosity of 3 fb$^{-1}$, collected by the LHCb experiment. The measured value of the $\bar{B}_s^0\to D_s^-D_s^+$ Effective Lifetime is $1.379\pm0.026\pm0.017$ ps, where the uncertainties are statistical and systematic, respectively. This Lifetime translates into a measurement of the decay width of the light $\bar{B}_s^0$ mass eigenstate of \Gamma_L$=0.725\pm0.014\pm0.009$ ps$^{-1}$. The $\bar{B}_s^0$ Lifetime is also measured using the flavor-specific $\bar{B}_s^0\to D^-D_s^+$ decay to be $1.52\pm0.15\pm0.01 {\rm ps}$.
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Measurement of the Bs Effective Lifetime in the J/psi fo(980) final state
Physical Review Letters, 2012Co-Authors: R. Aaij, S. Barsuk, O. Callot, B. Jean-marie, J. Lefrançois, F. Machefert, A. Martin Sanchez, M. Nicol, P. Robbe, M.-h. SchuneAbstract:The Effective Lifetime of the Bs meson in the decay mode Bs->J/\psi fo(980) is measured using 1.0/fb of data collected in pp collisions at sqrt(s) = 7 TeV with the LHCb detector. The result is 1.700 +/- 0.040 +/- 0.026 ps where the first uncertainty is statistical and the second systematic. As the final state is CP-odd, and CP violation in this mode is measured to be small, the Lifetime measurement can be translated into a measurement of the decay width of the heavy Bs mass eigenstate, \Gamma_H = (0.588 +/- 0.014 +/- 0.009)/ps.