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Your search keyword '"Khalil El Hajraoui"' showing total 10 results
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10 results on '"Khalil El Hajraoui"'

1. High-spatial resolution functional chemistry of nitrogen compounds in the observed UK meteorite fall Winchcombe

Author

Christian Vollmer, Demie Kepaptsoglou, Jan Leitner, Aleksander B. Mosberg, Khalil El Hajraoui, Ashley J. King, Charlotte L. Bays, Paul F. Schofield, Tohru Araki, and Quentin M. Ramasse

Subjects
Science
Abstract

Abstract Organic matter in extraterrestrial samples is a complex material that might have played an important role in the delivery of prebiotic molecules to the early Earth. We report here on the identification of nitrogen-containing compounds such as amino acids and N-heterocycles within the recent observed meteorite fall Winchcombe by high-spatial resolution spectroscopy techniques. Although nitrogen contents of Winchcombe organic matter are low (N/C ~ 1–3%), we were able to detect the presence of these compounds using a low-noise direct electron detector. These biologically relevant molecules have therefore been tentatively found within a fresh, minimally processed meteorite sample by high spatial resolution techniques conserving the overall petrographic context. Carbon functional chemistry investigations show that sizes of aromatic domains are small and that abundances of carboxylic functional groups are low. Our observations demonstrate that Winchcombe represents an important addition to the collection of carbonaceous chondrites and still preserves pristine extraterrestrial organic matter.

Published
2024
Full Text
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2. Tuning the 1T′/2H phases in WxMo1−xSe2 nanosheets

Author

Maria S. Sokolikova, Gang Cheng, Mauro Och, Pawel Palczynski, Khalil El Hajraoui, Quentin M. Ramasse, and Cecilia Mattevi

Subjects
General Materials Science
Abstract

Nanomaterial morphology, chemical composition and 1T′/2H crystal phase tuning is achieved in colloidal WxMo1−xSe2 nanosheets synthesised by a direct colloidal reaction.

Published
2023

3. Van Der Waals Heteroepitaxy of GaSe and InSe, Quantum Wells and Superlattices

Author

Marcel S. Claro, Juan P. Martínez‐Pastor, Alejandro Molina‐Sánchez, Khalil El Hajraoui, Justyna Grzonka, Hamid Pashaei Adl, David Fuertes Marrón, Paulo J. Ferreira, Oleksandr Bondarchuk, and Sascha Sadewasser

Subjects
Condensed Matter - Materials Science, Condensed Matter - Mesoscale and Nanoscale Physics, Materials Science (cond-mat.mtrl-sci), FOS: Physical sciences, Physics::Optics, Applied Physics (physics.app-ph), Physics - Applied Physics, Condensed Matter Physics, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, Electronic, Optical and Magnetic Materials, Biomaterials, Condensed Matter::Materials Science, Mesoscale and Nanoscale Physics (cond-mat.mes-hall), Electrochemistry
Abstract

Bandgap engineering and quantum confinement in semiconductor heterostructures provide the means to fine-tune material response to electromagnetic fields and light in a wide range of the spectrum. Nonetheless, forming semiconductor heterostructures on lattice-mismatched substrates has been a challenge for several decades, leading to restrictions for device integration and the lack of efficient devices in important wavelength bands. Here, we show that the van der Waals epitaxy of two-dimensional (2D) GaSe and InSe heterostructures occur on substrates with substantially different lattice parameters, namely silicon and sapphire. The GaSe/InSe heterostructures were applied in the growth of quantum wells and superlattices presenting photoluminescence and absorption related to interband transitions. Moreover, we demonstrate a self-powered photodetector based on this heterostructure on Si that works in the visible-NIR wavelength range. Fabricated at wafer-scale, these results pave the way for an easy integration of optoelectronics based on these layered 2D materials in current Si technology., 16 Pages, 5 figures. Supplementary Information included in the end (+10 pages, +10 Figures, + 2 Tables). Partially presented at 21st ICMBE - September 2021

Published
2022

5. Selectivity boost in partial hydrogenation of acetylene via atomic dispersion of platinum over ceria

Author

Francis Leonard Deepak, Emanuele Barborini, S. Vinati, Jutta Kröhnert, Khalil El Hajraoui, Loukya Boddapati, Annette Trunschke, Yury V. Kolen'ko, and Olumide Bolarinwa Ayodele

Subjects
Cerium oxide, Materials science, 010405 organic chemistry, chemistry.chemical_element, 010402 general chemistry, 01 natural sciences, Catalysis, 0104 chemical sciences, chemistry.chemical_compound, Adsorption, Chemical engineering, chemistry, Acetylene, Selectivity, Platinum, Dispersion (chemistry), Pyrolysis
Abstract

High-throughput flame spray pyrolysis directly affords a low-loading Pt catalyst supported on cerium oxide, which is an excellent material for selective semihydrogenation of C2H2 at 180 °C, exhibiting nearly complete conversion of C2H2 (98.2%) with high selectivity towards C2H4 (87.1%). Pt in this catalyst is atomically dispersed within cerium oxide, and this structural feature restricts C2H4 adsorption as π-bonded, known to promote C2H4 selectivity.

Published
2020

6. Micro-sized thin-film solar cells via area-selective electrochemical deposition for concentrator photovoltaics application

Author

Finn Babbe, Khalil El Hajraoui, Phillip J. Dale, Pedro Anacleto, Francis Leonard Deepak, S. Tombolato, Kamal Abderrafi, Sascha Sadewasser, Max Hilaire Wolter, Alberto Lomuscio, and Daniel Siopa

Subjects
Materials science, Annealing (metallurgy), Energy science and technology, lcsh:Medicine, 02 engineering and technology, Electrochemistry, 01 natural sciences, Article, Metal, 0103 physical sciences, lcsh:Science, 010302 applied physics, Multidisciplinary, business.industry, Photovoltaic system, Energy conversion efficiency, lcsh:R, 021001 nanoscience & nanotechnology, Microelectrode, Chemistry, Semiconductor, visual_art, visual_art.visual_art_medium, Optoelectronics, lcsh:Q, 0210 nano-technology, business, Voltage
Abstract

Micro-concentrator solar cells enable higher power conversion efficiencies and material savings when compared to large-area non-concentrated solar cells. In this study, we use materials-efficient area-selective electrodeposition of the metallic elements, coupled with selenium reactive annealing, to form Cu(In,Ga)Se2 semiconductor absorber layers in patterned microelectrode arrays. This process achieves significant material savings of the low-abundance elements. The resulting copper-poor micro-absorber layers’ composition and homogeneity depend on the deposition charge, where higher charge leads to greater inhomogeneity in the Cu/In ratio and to a patchy presence of a CuIn5Se8 OVC phase. Photovoltaic devices show open-circuit voltages of up to 525 mV under a concentration factor of 18 ×, which is larger than other reported Cu(In,Ga)Se2 micro-solar cells fabricated by materials-efficient methods. Furthermore, a single micro-solar cell device, measured under light concentration, displayed a power conversion efficiency of 5% under a concentration factor of 33 ×. These results show the potential of the presented method to assemble micro-concentrator photovoltaic devices, which operate at higher efficiencies while using light concentration.

Published
2020

7. In Situ Transmission Electron Microscopy Analysis of Copper–Germanium Nanowire Solid-State Reaction

Author

Khalil El hajraoui, Eric Robin, Clemens Zeiner, Alois Lugstein, Stéphanie Kodjikian, Jean-Luc Rouvière, Martien Den Hertog, Matériaux, Rayonnements, Structure (MRS), Institut Néel (NEEL), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Institute of Solid State Physics, Technical University of Vienna (TUW), Vienna University of Technology (TU Wien), Optique et microscopies (POM), Laboratoire d'Etude des Matériaux par Microscopie Avancée (LEMMA ), Modélisation et Exploration des Matériaux (MEM), Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), ANR-12-JS10-0002,COSMOS,Correlation du microscopie électronique en transmission avec des mesures optique et électrique effectués sur le même nanofils unique(2012), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF), Institut de Physique de Rennes (IPR), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), Technical University of Vienna [Vienna] (TU WIEN), Optique et microscopies (POM ), Laboratoire d'Etude des Matériaux par Microscopie Avancée (LEMMA), Université Grenoble Alpes (UGA)-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes (UGA)-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Matériaux, Rayonnements, Structure (NEEL - MRS), Institut Nanosciences et Cryogénie (INAC), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Optique & Microscopies (NEEL - POM), and Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG)

Subjects
010302 applied physics, [PHYS]Physics [physics], Mechanical Engineering, In-situ Transmission Electron Microscopy, Surface Diffusion, Ge nanowires, Bioengineering, 02 engineering and technology, General Chemistry, [CHIM.INOR]Chemical Sciences/Inorganic chemistry, 021001 nanoscience & nanotechnology, Condensed Matter Physics, 01 natural sciences, Energy Dispersive X-ray Spectroscopy, 0103 physical sciences, General Materials Science, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], [SPI.NANO]Engineering Sciences [physics]/Micro and nanotechnologies/Microelectronics, 0210 nano-technology, ComputingMilieux_MISCELLANEOUS, Solid-state reaction
Abstract

International audience; A promising approach of making high quality contacts on semiconductors is a silicidation (for silicon) or germanidation (for germanium) annealing process, where the metal enters the semiconductor and creates a low resistance intermetallic phase. In a nanowire, this process allows one to fabricate axial heterostructures with dimensions depending only on the control and understanding of the thermally induced solid-state reaction. In this work, we present the first observation of both germanium and copper diffusion in opposite directions during the solid-state reaction of Cu contacts on Ge nanowires using in situ Joule heating in a transmission electron microscope. The in situ observations allow us to follow the reaction in real time with nanometer spatial resolution. We follow the advancement of the reaction interface over time, which gives precious information on the kinetics of this reaction. We combine the kinetic study with ex situ characterization using model-based energy dispersive X-ray spectroscopy (EDX) indicating that both Ge and Cu diffuse at the surface of the created Cu3Ge segment and the reaction rate is limited by Ge surface diffusion at temperatures between 360 and 600 °C. During the reaction, germanide crystals typically protrude from the reacted NW part. However, their formation can be avoided using a shell around the initial Ge NW. Ha direct Joule heating experiments show slower reaction speeds indicating that the reaction can be initiated at lower temperatures. Moreover, they allow combining electrical measurements and heating in a single contacting scheme, rendering the Cu–Ge NW system promising for applications where very abrupt contacts and a perfectly controlled size of the semiconducting region is required. Clearly, in situ TEM is a powerful technique to better understand the reaction kinetics and mechanism of metal–semiconductor phase formation.

Published
2019

8. In Situ Transmission Electron Microscopy Analysis of Aluminum–Germanium Nanowire Solid-State Reaction

Author

C. Zeiner, Martien Den Hertog, Khalil El Hajraoui, Eric Robin, Alois Lugstein, Jean-Luc Rouvière, Stéphanie Kodjikian, Matériaux, Rayonnements, Structure (NEEL - MRS), Institut Néel (NEEL), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Laboratoire d'Etude des Matériaux par Microscopie Avancée (LEMMA ), Modélisation et Exploration des Matériaux (MEM), Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Vienna University of Technology (TU Wien), Silicon Nanoelectronics Photonics and Structures (SiNaps), PHotonique, ELectronique et Ingénierie QuantiqueS (PHELIQS), Matériaux, Rayonnements, Structure [?-2015] (MRS [?-2015]), Institut Néel [2007-2015] (NEEL [2007-2015]), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology [2007-2019] (Grenoble INP [2007-2019])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology [2007-2019] (Grenoble INP [2007-2019])-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Etude des Matériaux par Microscopie Avancée [?-2019] (LEMMA [?-2019]), Institute of Solid State Physics, Technical University of Vienna (TUW), Technical University of Vienna [Vienna] (TU WIEN), Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Matériaux, Rayonnements, Structure (MRS), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])

Subjects
Ge nanowire, Materials science, Analytical chemistry, Energy-dispersive X-ray spectroscopy, Nanowire, chemistry.chemical_element, Bioengineering, Germanium, 02 engineering and technology, [CHIM.INOR]Chemical Sciences/Inorganic chemistry, aluminum contact, Reaction rate, energy dispersive X-ray spectroscopy, General Materials Science, Diffusion (business), ComputingMilieux_MISCELLANEOUS, in situ transmission electron microscopy, Surface diffusion, solid state reaction, Mechanical Engineering, diffusion, General Chemistry, [CHIM.MATE]Chemical Sciences/Material chemistry, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Electrical contacts, chemistry, Electron diffraction, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], 0210 nano-technology
Abstract

International audience; To fully exploit the potential of semiconduct-ing nanowires for devices, high quality electrical contacts are of paramount importance. This work presents a detailed in situ transmission electron microscopy (TEM) study of a very promising type of NW contact where aluminum metal enters the germanium semiconducting nanowire to form an extremely abrupt and clean axial metal−semiconductor interface. We study this solid-state reaction between the aluminum contact and germanium nanowire in situ in the TEM using two different local heating methods. Following the reaction interface of the intrusion of Al in the Ge nanowire shows that at temperatures between 250 and 330°C the position of the interface as a function of time is well fitted by a square root function, indicating that the reaction rate is limited by a diffusion process. Combining both chemical analysis and electron diffraction we find that the Ge of the nanowire core is completely exchanged by the entering Al atoms that form a monocrystalline nanowire with the usual face-centered cubic structure of Al, where the nanowire dimensions are inherited from the initial Ge nanowire. Model-based chemical mapping by energy dispersive X-ray spectroscopy (EDX) characterization reveals the three-dimensional chemical cross-section of the transformed nanowire with an Al core, surrounded by a thin pure Ge (∼2 nm), Al 2 O 3 (∼3 nm), and Ge containing Al 2 O 3 (∼1 nm) layer, respectively. The presence of Ge containing shells around the Al core indicates that Ge diffuses back into the metal reservoir by surface diffusion, which was confirmed by the detection of Ge atoms in the Al metal line by EDX analysis. Fitting a diffusion equation to the kinetic data allows the extraction of the diffusion coefficient at two different temperatures, which shows a good agreement with diffusion coefficients from literature for self-diffusion of Al.

Published
2019

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