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Urea-assisted morphological engineering of MFI nanosheets with tunable b-thickness

Nano Research 2023年第10期16卷 12196-12206页

作者： Qiudi Yue Chaowei Liu Hongjuan Zhao Honghai Liu pierre ruterana Jiaqi Zhao Zhengxing Qin Svetlana Mintova Laboratoire Catalyse et Spectrochimie ENSICAENUNICAENCNRSCaen 14050France Petrochemical Research Institute PetroChina Company LimitedBeijing 100195China Centre de Recherche sur les Ions les Matériaux et la PhotoniqueCIMAP-ENSICAENCNRS UMR 6252Caen 14050France State Key Laboratory of Heavy Oil Processing College of Chemical EngineeringChina University of Petroleum(East China)Qingdao 266580China

Engineering of crystal morphology affects the catalytic and adsorption properties of zeolitic *** the anisotropic diffusion of molecules derived from its topological features,MFI zeolite nanosheets with short b-axis thickness are highly desired materials to reduce diffusion ***,the design and development of eco-friendly synthesis protocols with reasonable cost and high efficiency remain ***,we reported a systematic study on the synthesis of MFI nanosheets using urea as an *** silicalite-1 and ZSM-5 zeolites(MFI type framework structure)with controllable b-thicknesses ranging from 50–200 nm were achieved by optimizing the synthetic parameters including water content,urea and SDA *** concentration of hydroxide anions was found to dominate the crystallization kinetics compared with the counterpart tetrapropylammonium cations(TPA^(+)).To facilitate the crystal growth of MFI zeolites in the presence of urea,the ratio OH−/SiO_(2)has to be higher than 0.2,independent of the TPA+*** role of urea in the assistance of plate-like crystal formation through the inhibition of(010)facet growth was revealed by electron microscopy and infrared(IR)spectroscopy *** developed strategy for morphological engineering is not limited to the MFI-type zeolite and can be applied to other frameworks depending on the intrinsic properties of additive molecules and the interactions between them.

关键词： MFI zeolite synthesis nanosheets additives crystal morphology

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Research on fabrication and properties of nanoporous GaN epilayers

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Rare Metals 2006年第Z2期25卷 5-10页

作者： NOUET Gérard ruterana pierre Laboratoire Structures des Interfaces et Fonctionnalité des Couches Minces UMR CNRS 6176 ENSICAEN6 Boulevard du Maréchal Juin 14050 Caen Cedex France

Gallium nitride (GaN) epilayers with nanopore arrays were fabricated by inductive coupled plasma (ICP) etching using anodic aluminum oxide (AAO) as mask. Nanoporous AAO templates were formed by anodizing the Al films deposited on GaN epilayers. The diameter of the perforations in the AAO masks could be easily controlled by tuning the technique parameters of AAO fabrication process. Cl2/Ar and Cl2/He were employed as etching gas. Scanning electron microscopy (SEM) analysis shows that vertical nanoporous arrays with uniform distribution can directly be transferred from AAO masks to GaN films in some proper conditions. Photoluminescence (PL) spectra, X-ray diffraction (XRD) and Raman spectroscopy were applied to assess properties of the nanoporous GaN films with different average pore diameters and interpore distances.

关键词： nanoporous GaN ICP etching

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Growth of high-quality thick GaN using a tungsten interlayer

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Rare Metals 2006年第Z2期25卷 11-14页

作者： NOUET Gérard ruterana pierre Laboratoire Structures des Interfaces et Fonctionnalité des Couches Minces UMR CNRS 6176 ENSICAEN 6 Boulevard du Maréchal Juin 14050 Caen Cedex France

A high-quality GaN film was (W-GaN) grown by hydride vapor phase epitaxy (HVPE) on metalorganic chemical vapor deposition (MOCVD) GaN templates with a tungsten (W) interlayer. A sample without interlayer was also grown at the same time for comparison. Significant reductions of dislocation density in W-GaN film is confirmed by the result of high-resolution X-ray diffraction and transmission electron microscope (TEM) observation. The improvement of optical properties of the W-GaN is confirmed by photoluminescence (PL) result. A shift of PL peak suggests that the strain is lower in the W-GaN than the film without W interlayer. This technique offers a potential path to obtain high-quality GaN film as free-standing substrate.

关键词： GaN tungsten interlayer HVPE HRXRD

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Effect of AlN intermediate layer on growing GaN film by hydride vapor phase epitaxy

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Rare Metals 2006年第Z2期25卷 15-19页

作者： NOUET Gérard2 ruterana pierre Laboratoire Structures des Interfaces et Fonctionnalité des Couches Minces UMR CNRS 6176 ENSICAEN6 Boulevard du Maréchal Juin 14050 Caen Cedex France

Thick GaN layer deposited by hydride vapor phase epitaxy (HVPE) on a metalorganic chemical vapor deposition (MOCVD) GaN template with a thin low temperature (LT) AlN intermediate layer was investigated. High resolution X-ray resolution diffraction (HRXRD) shows that the crystalline quality of thick GaN layer was improved compared with the template. As confirmed by atomic force microscopy (AFM) observations, the surface morphology of AlN intermediate layer helps to improve the nucleation of GaN epilayer. Photoluminescence (PL) spectra measurement shows its high optical quality and low compressive stress, and micro Raman measurement confirms the latter result. Thus, the deposition of the LT-AlN interlayer has promoted the growth of an HVPE-GaN layer with an excellent crystalline quality.

关键词： GaN AlN intermediate layer HVPE HRXRD AFM photoluminescence

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Atomic core structure of 90°c■bent screw threading dislocations in wurtzite GaN

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Rare Metals 2006年第S2期25卷 1-4页

作者： BELABBAS Imad ruterana pierre NOUET Gérard Laboratoire Structure des Interfaces et Fonctionnalité des Couches Minces UMR CNRS 6176 Ecole Nationale Supérieure d′Ingénieurs de Caen 6 Bld du Maréchal Juin 14050 Caen cedex France

The atomic and electronic structures of the c threading dislocations with an edge or screw character were compared using a tight binding formalism which takes into account charge transfer. The two dislocations do not exhibit dangling bonds. While the screw dislocation contains only constrained Ga-N bonds, the edge dislocation contains Ga-Ga and N-N wrong bonds. Both dislocations are found to induce shallow and deep gap states.

关键词： GaN dislocations SCC-DFTB

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