60 research outputs found
Absolute surface and interface energy analysis of III-V/Si and its consequences on wetting characteristics
No full textInternational audienceIntegration of III-V semiconductors on Si (001) substrates is of great interest for photonic, electronic, and energy harvesting devices. [1-3] In this study, we show how the atomic arrangement of the III-V/Si interface affects the system's wetting characteristics. Using density functional theory, we first demonstrate how it is possible to investigate the variations of the absolute interface energy with the chemical potential in heterogeneous materials systems. Especially, we show that charge compensated III-V/Si interfaces are remarkably stable over a large range of chemical potential in agreement with the Electron counting model. [4,5] Although it is anticipated that stable compensated III-V/Si interfaces would normally favor complete wetting conditions, it is found that this can be easily balanced by the substrate's initial passivation, which favors in turn partial wetting conditions. Finally, we highlight how surface passivation is crucial in wetting property investigations during heterogeneous epitaxy.This research was supported by the French National Research NUAGES Project (Grant no. ANR-21-CE24- 0006). DFT calculations were performed at FOTON Institute, and the work was granted access to the HPC resources of TGCC/CINES under the allocation A0120911434 and A0140911434 made by GENCI. [1] I. Lucci, S. Charbonnier, L. Pedesseau, M. Vallet, L. Cerutti, J.-B. Rodriguez, E. Tournié, R. Bernard, A. Létoublon, N. Bertru, A. Le Corre, S. Rennesson, F. Semond, G. Patriarche, L. Largeau, P. Turban, A. Ponchet, and C. Cornet, Phys. Rev. Materials 2(6), 060401 (2018)[2] I. Lucci, S. Charbonnier, M. Vallet, P. Turban, Y. Léger, T. Rohel, N. Bertru, A. Létoublon, J. Rodriguez, L. Cerutti, E. Tournié, A. Ponchet, G. Patriarche, L. Pedesseau, and C. Cornet, Adv Funct Materials 28(30), 1801585 (2018). [3] C. Cornet, S. Charbonnier, I. Lucci, L. Chen, A. Létoublon, A. Alvarez, K. Tavernier, T. Rohel, R. Bernard, J.-B. Rodriguez, L. Cerutti, E. Tournié, Y. Léger, M. Bahri, G. Patriarche, L. Largeau, A. Ponchet, P. Turban, and N. Bertru, Phys. Rev. Materials 4(5), 053401 (2020)[4] O. Supplie, S. Brückner, O. Romanyuk, H. Döscher, C. Höhn, M. M. May, P. Kleinschmidt, F. Grosse, and T. Hannappel, Phys. Rev. B 90, 235301 (2014). [5] S. Pallikkara Chandrasekharan, I. Lucci, D. Gupta, C. Cornet, and L. Pedesseau, Phys. Rev. B 108(7), 075305 (2023)
Heteroepitaxial growth of III-V on Si: a DFT perspective
No full textInternational audienceUnderstanding the physical properties of heterogeneous integration, such as the epitaxial growth of III-V on Si, is highly desirable for more advanced and futuristic optoelectronic and photoelectric applications of semiconductors [1, 2]. Using density functional theory, we first demonstrate how it is possible to investigate the absolute surface and interface energies with the variations of chemical potential for heterogeneous materials systems [3, 4]. Then, we show how to quantify the impact of Si surface passivation before III-V/Si hetero-epitaxy on the surface energy of the Si initial substrate, which plays an essential role in establishing its wetting characteristics on the specific case of GaP/Si [5]. In addition, we highlight that this inevitable passivation leads to a considerable reduction of the substrate surface energy, which in turn leads to a significant decrease in spreading parameters and evidence the heteroepitaxy in 3D Volmer-Weber type. Finally, we explore the possibilities to have a full ab initio description of Wulff-Kaishew equilibrium morphology prediction.[1] I. Lucci, S. Charbonnier, M. Vallet, P. Turban, Y. Léger, T. Rohel, N. Bertru, A. Létoublon, J. Rodriguez, L. Cerutti, E. Tournié, A. Ponchet, G. Patriarche, L. Pedesseau, and C. Cornet, Adv Funct Materials 28(30), 1801585 (2018). [2] C. Cornet, S. Charbonnier, I. Lucci, L. Chen, A. Létoublon, A. Alvarez, K. Tavernier, T. Rohel, R. Bernard, J.-B. Rodriguez, L. Cerutti, E. Tournié, Y. Léger, M. Bahri, G. Patriarche, L. Largeau, A. Ponchet, P. Turban, and N. Bertru, Phys. Rev. Materials 4(5), 053401 (2020). [3] I. Lucci, S. Charbonnier, L. Pedesseau, M. Vallet, L. Cerutti, J.-B. Rodriguez, E. Tournié, R. Bernard, A. Létoublon, N. Bertru, A. Le Corre, S. Rennesson, F. Semond, G. Patriarche, L. Largeau, P. Turban, A. Ponchet, and C. Cornet, Phys. Rev. Materials 2(6), 060401(R) (2018). [4] S. Pallikkara Chandrasekharan, I. Lucci, D. Gupta, C. Cornet, and L. Pedesseau, Phys. Rev. B 108(7), 075305 (2023). [5] S. Pallikkara Chandrasekharan, D. Gupta, C. Cornet, and L. Pedesseau, Phys. Rev. B 109(4), 045304 (2024)
Impact of initial surface passivation on wetting properties analysis during III-V/Si epitaxy
No full textInternational audienceThe co-integration of III-V semiconductors on Si (001) substrates is highly desirable for energy harvesting, electronics, and photonic applications. [1-3] Understanding surface passivation prior to any heterogeneous integration of materials through epitaxy is a cornerstone to establish the wetting characteristics in a material system. [4] Using DFT simulations, we highlight how to quantitatively determine the impact of Si surface passivation prior to III-V/Si hetero-epitaxy on the surface energy of the Si initial substrate. Then, we explore its consequences for the description of wetting properties on the specific case of GaP/Si heterogeneous growth. [5] We show that this inevitable passivation on Si prior to GaP/Si heteroepitaxy leads to a large decrease of the substrate surface energy. This, in turn, leads to a significant decrease in the spreading parameter for the studied system. In addition, we demonstrate that the stabilization of the initial Si surface through passivation is a driving force for 3D Volmer-Weber crystal growth. Finally, it is established that a complete wetting situation would become possible if the passivated Si surface could be destabilized by at least 15 meV/Ų or if the III-V (001) surface could be stabilized by the same amount.This research was supported by the French National Research NUAGES Project (Grant no. ANR-21-CE24-0006). DFT calculations were performed at FOTON Institute, and the work was granted access to the HPC resources of TGCC/CINES under the allocation A0120911434 and A0140911434 made by GENCI.[1] I. Lucci, S. Charbonnier, L. Pedesseau, M. Vallet, L. Cerutti, J.-B. Rodriguez, E. Tournié, R. Bernard, A. Létoublon, N. Bertru, A. Le Corre, S. Rennesson, F. Semond, G. Patriarche, L. Largeau, P. Turban, A. Ponchet, and C. Cornet, Phys. Rev. Materials 2(6), 060401 (2018).[2] I. Lucci, S. Charbonnier, M. Vallet, P. Turban, Y. Léger, T. Rohel, N. Bertru, A. Létoublon, J. Rodriguez, L. Cerutti, E. Tournié, A. Ponchet, G. Patriarche, L. Pedesseau, and C. Cornet, Adv Funct Materials 28(30), 1801585 (2018).[3] C. Cornet, S. Charbonnier, I. Lucci, L. Chen, A. Létoublon, A. Alvarez, K. Tavernier, T. Rohel, R. Bernard, J.-B. Rodriguez, L. Cerutti, E. Tournié, Y. Léger, M. Bahri, G. Patriarche, L. Largeau, A. Ponchet, P. Turban, and N. Bertru, Phys. Rev. Materials 4(5), 053401 (2020).[4] S. Pallikkara Chandrasekharan, I. Lucci, D. Gupta, C. Cornet, and L. Pedesseau, Phys. Rev. B 108(7), 075305 (2023).[5] S. Pallikkara Chandrasekharan, D. Gupta, C. Cornet, and L. Pedesseau, Phys. Rev. B 109(4), 045304 (2024)
Mineralogical characterization and dissolution experiments in Gamble's solution of tremolitic amphibole from Passo di Caldenno (Sondrio, Italy)
No full textIn nature, asbestos is often associated with minerals and other non-asbestiform morphologies thought to be harmless, but not much is known about the potential toxic effects of these phases. Therefore, the characterization of natural assemblages should not be limited to asbestos fibers only. This paper combines a multi-analytical characterization of asbestos from Valmalenco (Italy) with data from dissolution experiments conducted in a simulated interstitial lung fluid (Gamble’s solution), and a detailed dimensional study that compares the particle population before and after this interaction. The sample is identified as a tremolitic amphibole, exhibiting a predominance of fiber and prismatic habits at lower magnification, but a bladed habit at higher magnification. The results show that at different magnification, the dimensional and habit distributions are notably different. After the dissolution experiments, the sample showed rounded edges and pyramid-shaped dissolution pits. Chemical analyses suggested that a nearly stoichiometric logarithmic loss of Si and Mg occurred associated with a relatively intense release of Ca in the first 24 h, whereas Fe was probably redeposited on the fiber surfaces. A rearrangement of the more frequent habits and dimensions was recorded after the dissolution experiment, with a peculiar increase of the proportion of elongated mineral particles
Atomic scale description of III-V/Si (001) heteroepitaxial crystals
No full textInternational audienceHeteroepitaxy, such as the co-integration of III-V semiconductors on Si (001) substrates, is poised to meet tomorrow’s energy harvesting and opto-electronic applications needs [1-3]. A fundamental understanding of in-situ hetero-epitaxial growth requires a deep knowledge of nucleation at the atomistic level. Using density functional theory, we established the methodology to obtain the absolute surface and interface energies, allowing us to quantitatively determine the wetting behavior of the system [4,5]. In this work, we show how a freshly-prepared Si substrate, is naturally passivated when inserted in an epitaxial chamber, by either a group-III or a group-V monoatomic coverage, resulting in large stabilization of its surface energy [6]. Especially, we show its drastic impact on the wetting properties of GaP on Si, promoting 3D Volmer-Weber growth mode. With these findings, a synthetic description of surface and interface energies ranges expected during III-V/Si epitaxy can be given. Finally, we demonstrate how the knowledge of surface and interface energies in the system allows to give a full ab initio prediction of the Wulff-Kaishew equilibrium morphology of III-V/Si islands at the equilibrium.This research was supported by the French National Research NUAGES Project (Grant no. ANR-21-CE24-0006). DFT calculations were performed at FOTON Institute, and the work was granted access to the HPC resources of TGCC/CINES under the allocation A0160911434 and A0140911434 made by GENCI.[1] I. Lucci, S. Charbonnier, M. Vallet, P. Turban, Y. Léger, T. Rohel, N. Bertru, A. Létoublon, J. Rodriguez, L. Cerutti, E. Tournié, A. Ponchet, G. Patriarche, L. Pedesseau, and C. Cornet, Adv Funct Materials 28(30), 1801585 (2018).[2] M. Feifel, J. Ohlmann, J. Benick, M. Hermle, J. Belz, A. Beyer, K. Volz, T. Hannappel, A. W. Bett, D. Lackner et al., IEEE J. Photovolt. 8, 1590 (2018).[3] M. Piriyev, G. Loget, Y. Léger, L. Chen, A. Létoublon, T. Rohel, C. Levallois, J. Le Pouliquen, B. Fabre, N. Bertru et al., Sol. Energy Mater. Sol. Cells 251, 112138 (2023).[4] I. Lucci, S. Charbonnier, L. Pedesseau, M. Vallet, L. Cerutti, J.-B. Rodriguez, E. Tournié, R. Bernard, A. Lé-toublon, N. Bertru, A. Le Corre, S. Rennesson, F. Semond, G. Patriarche, L. Largeau, P. Turban, A. Ponchet, and C. Cornet, Phys. Rev. Materials 2(6), 060401(R) (2018).[5] S. Pallikkara Chandrasekharan, I. Lucci, D. Gupta, C. Cornet, and L. Pedesseau, Phys. Rev. B 108(7), 075305 (2023).[6] S. Pallikkara Chandrasekharan, D. Gupta, C. Cornet, and L. Pedesseau, Phys. Rev. B 109(4), 045304 (2024)
Risk factors for respiratory failure among hospitalized patients with Guillain–Barré syndrome
No full textBackground: Guillain–Barré syndrome (GBS) is an acute inflammatory polyneuropathy that can lead to respiratory failure. In this study, we evaluate early clinical risk factors for respiratory failure at the time of hospital admission. Methods: We studied a retrospective cohort of patients with GBS admitted to a tertiary care center. The potential risk factors studied were sociodemographic characteristics, GBS symptoms, overall and cervical muscle weakness (Medical Research Council [MRC] scores), electromyography findings, and cerebrospinal fluid analysis findings. Unadjusted odds ratios (OR) were calculated and exact logistic regression analysis (adjusted OR) performed to assess the association between baseline risk factors and respiratory failure. Results: Overall, 13 of 113 (12%) patients included in the study developed respiratory failure. Unadjusted analyses showed that involvement of any cranial nerve (OR: 14.7; 95% CI, 1.8–117.1), facial palsy (OR: 17.3; 95% CI, 2.2–138.0), and bulbar weakness (OR: 10.7; 95% CI, 2.3–50.0) were associated with increased risk of respiratory failure. Lower MRC sum scores (for scores 3) were independently associated with respiratory failure. Conclusions: Bulbar and neck muscle weakness at admission are clinical predictors of increased risk of respiratory failure in patients with GBS. These findings could guide the adequate management of high-risk patients. Resumen: Introducción: El síndrome de Guillain-Barré es una polineuropatía inflamatoria aguda que puede causar insuficiencia respiratoria. Evaluamos los factores de riesgo clínicos en el momento de la hospitalización. Métodos: Realizamos un estudio de una cohorte retrospectiva de pacientes con síndrome de Guillain-Barré hospitalizados en un centro de tercer nivel. Analizamos las características sociodemográficas, síntomas de la enfermedad, fuerza muscular general y cervical (escala del Medical Research Council [MRC]), hallazgos electromiográficos, y resultados del análisis del líquido cefalorraquídeo. Calculamos el odds ratio (OR) sin ajustar y realizamos una regresión logística exacta (OR ajustada) para evaluar la asociación entre los factores de riesgo y la insuficiencia respiratoria. Resultados: Trece de los 113 pacientes incluidos (12%) presentó insuficiencia respiratoria. Los análisis no ajustados mostraron una asociación entre mayor riesgo de insuficiencia respiratoria y la afectación de cualquier par craneal (OR: 14,7; IC 95%, 1,8-117,1), parálisis facial (OR: 17,3; IC 95%, 2,2-138,0) y debilidad bulbar (OR: 10,7; IC 95%, 2,3-50,0). Unas puntuaciones más bajas en la MRC-total (puntuaciones 3) se asociaron de forma independiente con la insuficiencia respiratoria. Conclusiones: La presencia de debilidad bulbar y cervical en el momento de la hospitalización es un factor de riesgo de insuficiencia respiratoria en pacientes con síndrome de Guillain-Barré. Estos hallazgos pueden servir de guía para el manejo de los pacientes con mayor riesgo de presentar dicha complicación
Pentraxin-3 as a Marker of Advanced Atherosclerosis Results from the Bruneck, ARMY and ARFY Studies
No full textPubMed ID: 22319633This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Left atrial appendage occlusion with Amplatzer Cardio Plug is an acceptable therapeutic option for prevention of stroke recurrence in patients with non-valvular atrial fibrillation and contraindication or failure of oral anticoagulation with acenocumarol
No full textABSTRACT Left atrial appendage occlusion (LAAO) appears as a therapeutic option for some atrial fibrillation patients not suitable for oral anticoagulation because an increased hemorrhagic risk or recurrent ischemic events despite anticoagulant treatment. Methods Report of consecutive atrial fibrillation patients treated with LAAO with Amplatzer Cardio Plug because contraindication or failure of oral anticoagulation with acenocumarol. CHA2DS2VASC, HAS-BLED, NIHSS, mRS, procedural complications and outcome were assessed. Seven patients (73 ± 6 year-old) were treated after intracerebral (n = 5) and gastrointestinal (n = 1) hemorrhages or ischemic stroke recurrence while on acenocumarol (n = 1). Results Mean follow up was 18 months. Baseline CHA2DS2Vasc y HAS-BLED scores were 5.6 ± 0.7 and 4.1 ± 0.3 respectively. There were no strokes or deaths. There was only one non-serious adverse event. Conclusion LAAO with ACP appears as a feasible therapeutic option for stroke prevention in patients with atrial fibrillation and failure or contraindication to acenocumarol
Author Correction: The spread of steppe and Iranian-related ancestry in the islands of the western Mediterranean
No full textCorrection to: Nature Ecology & Evolution https://doi.org/10.1038/s41559-020-1102-0, published online 24 February 2020.D.M.F. was supported by an Irish Research Council grant GOIPG/2013/36. Radiocarbon work was supported in part by the NSF Archaeometry program BCS-1460369 (to D.J.K. and B.J.C). C.L.-F. was supported by Obra Social La Caixa and by FEDER-MINECO (BFU2015-64699-P and PGC2018-095931-B-100). D.C. was supported by grant 20177PJ9XF MIUR PRIN 2017. D.Reich is an Investigator of the Howard Hughes Medical Institute, and his ancient-DNA laboratory work was supported by National Science Foundation HOMINID grant BCS-1032255, a National Institutes of Health grant GM100233, an Allen Discovery Center grant, and grant no. 61220 from the John Templeton Foundation
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