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Alain Portavoce - One of the best experts on this subject based on the ideXlab platform.

  • lattice diffusion and Surface Segregation of b during growth of sige heterostructures by molecular beam epitaxy effect of ge concentration and biaxial stress
    Journal of Applied Physics, 2004
    Co-Authors: Alain Portavoce, P. Gas, Isabelle Berbezier, Antoine Ronda, J. S. Christensen, B G Svensson
    Abstract:

    Si1−xGex∕Si1−yGey∕Si(100) heterostructures grown by molecular beam epitaxy were used in order to study B Surface Segregation during growth and B lattice diffusion. Ge concentration and stress effects were separated. Analysis of B Segregation during growth shows that (i) for layers in epitaxy on (100)Si, B Segregation decreases with increasing Ge concentration, i.e., with increased compressive stress; (ii) for unstressed layers, B Segregation increases with Ge concentration; (iii) at constant Ge concentration, B Segregation increases for layers in tension and decreases for layers in compression. The contrasting behaviors observed as a function of Ge concentration in compressively stressed and unstressed layers can be explained by an increase of the equilibrium Segregation driving force induced by Ge additions and an increase of near-Surface diffusion in compressively stressed layers. Analysis of lattice diffusion shows that (i) in unstressed layers, B lattice diffusion coefficient decreases with increasing...

  • sb Surface Segregation during epitaxial growth of sige heterostructures the effects of ge composition and biaxial stress
    Physical Review B, 2004
    Co-Authors: Alain Portavoce, P. Gas, Isabelle Berbezier, Antoine Ronda
    Abstract:

    Antimony is the most widely used n-type dopant for Si molecular-beam epitaxy (MBE). However, because of Surface Segregation during growth, the control of doping profiles remains difficult. The case of Si/Si 1 - x Ge x heterostructures is complicated by the existence of stresses, which may affect both the thermodynamics and kinetics of Segregation. In this study, we analyze the Segregation of Sb resulting from the MBE growth of Si 1 - x Ge x /Si(100) heterostructures using secondary ion mass spectrometry as a function of (i) growth temperature (200°C≤T°≤550°C), (ii) germanium content (0≤x≤0.2), and (iii) stresses (compressively strained and relaxed layers). We show that Sb Segregation: (i) increases with temperature, (ii) increases with Ge content in biaxially compressed layers, (iii) decreases with Ge content in relaxed layers. The temperature variation indicates that Sb Surface Segregation during growth is kinetically controlled. The contrasting behaviors observed as a function of Ge content in stressed and relaxed layers can thus be explained by a decrease of the Segregation enthalpy induced by Ge addition and an increase of near-Surface diffusion in stressed layers.

  • Lattice diffusion and Surface Segregation of B during growth of SiGe heterostructures by molecular beam epitaxy: effect of Ge concentration and biaxial stress.
    Journal of Applied Physics, 2004
    Co-Authors: Alain Portavoce, P. Gas, Isabelle Berbezier, Antoine Ronda, J. S. Christensen, B. Svensson
    Abstract:

    Si1-xGex/Si1-yGey/Si(100) heterostructures grown by Molecular Beam Epitaxy (MBE) were used in order to study B Surface Segregation during growth and B lattice diffusion. Ge concentration and stress effects were separated. Analysis of B Segregation during growth shows that: i) for layers in epitaxy on (100)Si), B Segregation decreases with increasing Ge concentration, i.e. with increased compressive stress, ii) for unstressed layers, B Segregation increases with Ge concentration, iii) at constant Ge concentration, B Segregation increases for layers in tension and decreases for layers in compression. The contrasting behaviors observed as a function of Ge concentration in compressively stressed and unstressed layers can be explained by an increase of the equilibrium Segregation driving force induced by Ge additions and an increase of near-Surface diffusion in compressively stressed layers. Analysis of lattice diffusion shows that: i) in unstressed layers, B lattice diffusion coefficient decreases with increasing Ge concentration, ii) at constant Ge concentration, the diffusion coefficient of B decreases with compressive biaxial stress and increases with tensile biaxial stress, iii) the volume of activation of B diffusion ( ) is positive for biaxial stress while it is negative in the case of hydrostatic pressure. This confirms that under a biaxial stress the activation volume is reduced to the relaxation volume.

Antoine Ronda - One of the best experts on this subject based on the ideXlab platform.

  • lattice diffusion and Surface Segregation of b during growth of sige heterostructures by molecular beam epitaxy effect of ge concentration and biaxial stress
    Journal of Applied Physics, 2004
    Co-Authors: Alain Portavoce, P. Gas, Isabelle Berbezier, Antoine Ronda, J. S. Christensen, B G Svensson
    Abstract:

    Si1−xGex∕Si1−yGey∕Si(100) heterostructures grown by molecular beam epitaxy were used in order to study B Surface Segregation during growth and B lattice diffusion. Ge concentration and stress effects were separated. Analysis of B Segregation during growth shows that (i) for layers in epitaxy on (100)Si, B Segregation decreases with increasing Ge concentration, i.e., with increased compressive stress; (ii) for unstressed layers, B Segregation increases with Ge concentration; (iii) at constant Ge concentration, B Segregation increases for layers in tension and decreases for layers in compression. The contrasting behaviors observed as a function of Ge concentration in compressively stressed and unstressed layers can be explained by an increase of the equilibrium Segregation driving force induced by Ge additions and an increase of near-Surface diffusion in compressively stressed layers. Analysis of lattice diffusion shows that (i) in unstressed layers, B lattice diffusion coefficient decreases with increasing...

  • sb Surface Segregation during epitaxial growth of sige heterostructures the effects of ge composition and biaxial stress
    Physical Review B, 2004
    Co-Authors: Alain Portavoce, P. Gas, Isabelle Berbezier, Antoine Ronda
    Abstract:

    Antimony is the most widely used n-type dopant for Si molecular-beam epitaxy (MBE). However, because of Surface Segregation during growth, the control of doping profiles remains difficult. The case of Si/Si 1 - x Ge x heterostructures is complicated by the existence of stresses, which may affect both the thermodynamics and kinetics of Segregation. In this study, we analyze the Segregation of Sb resulting from the MBE growth of Si 1 - x Ge x /Si(100) heterostructures using secondary ion mass spectrometry as a function of (i) growth temperature (200°C≤T°≤550°C), (ii) germanium content (0≤x≤0.2), and (iii) stresses (compressively strained and relaxed layers). We show that Sb Segregation: (i) increases with temperature, (ii) increases with Ge content in biaxially compressed layers, (iii) decreases with Ge content in relaxed layers. The temperature variation indicates that Sb Surface Segregation during growth is kinetically controlled. The contrasting behaviors observed as a function of Ge content in stressed and relaxed layers can thus be explained by a decrease of the Segregation enthalpy induced by Ge addition and an increase of near-Surface diffusion in stressed layers.

  • Lattice diffusion and Surface Segregation of B during growth of SiGe heterostructures by molecular beam epitaxy: effect of Ge concentration and biaxial stress.
    Journal of Applied Physics, 2004
    Co-Authors: Alain Portavoce, P. Gas, Isabelle Berbezier, Antoine Ronda, J. S. Christensen, B. Svensson
    Abstract:

    Si1-xGex/Si1-yGey/Si(100) heterostructures grown by Molecular Beam Epitaxy (MBE) were used in order to study B Surface Segregation during growth and B lattice diffusion. Ge concentration and stress effects were separated. Analysis of B Segregation during growth shows that: i) for layers in epitaxy on (100)Si), B Segregation decreases with increasing Ge concentration, i.e. with increased compressive stress, ii) for unstressed layers, B Segregation increases with Ge concentration, iii) at constant Ge concentration, B Segregation increases for layers in tension and decreases for layers in compression. The contrasting behaviors observed as a function of Ge concentration in compressively stressed and unstressed layers can be explained by an increase of the equilibrium Segregation driving force induced by Ge additions and an increase of near-Surface diffusion in compressively stressed layers. Analysis of lattice diffusion shows that: i) in unstressed layers, B lattice diffusion coefficient decreases with increasing Ge concentration, ii) at constant Ge concentration, the diffusion coefficient of B decreases with compressive biaxial stress and increases with tensile biaxial stress, iii) the volume of activation of B diffusion ( ) is positive for biaxial stress while it is negative in the case of hydrostatic pressure. This confirms that under a biaxial stress the activation volume is reduced to the relaxation volume.

Zhongyi Jiang - One of the best experts on this subject based on the ideXlab platform.

  • incorporating dual defense mechanism with functionalized graphene oxide and perfluorosulfonic acid for anti fouling membranes
    Separation and Purification Technology, 2020
    Co-Authors: Yufeng Hao, Linjie Zhou, Zhongyi Jiang
    Abstract:

    Abstract Surface Segregation method based on the collaborative self-assembly principle was proposed to construct anti-fouling membranes with fouling-resistant and fouling-release mechanisms (dual-defense mechanism). Graphene oxides (GO) functionalized with polyethyleneimine (PEI) and perfluorosulfonic acid (PFSA) were added simultaneously into the casting solution to prepare PVDF/PFSA/PEI-GO hybrid membranes through Surface Segregation along with phase inversion process. The PEI-GO of hydrophilicity and the PFSA of low Surface energy were utilized as additives to incorporate dual-defense mechanism for anti-fouling membranes. Furthermore, the synergistic effect of PEI immobilized on GO and sulfonic acid groups on PFSA generated electrostatic interaction, improving the long-term stability of membranes in aqueous environment. In the oil/water separation performance experiments, PVDF/PFSA/PEI-GO-1% membranes exhibited the highest pure water permeability of 406.7 ± 15.6 L m−2 h−1 bar−1, with flux decay rate (DRt) of 8.6%, and flux recovery rate (FRR) of 98.6%.

  • achieving persistent high flux membranes via kinetic and thermodynamic synergistic manipulation of Surface Segregation process
    Journal of Membrane Science, 2017
    Co-Authors: Runnan Zhang, Yanan Liu, Lin Fan, Qi Zhang, Zhongyi Jiang
    Abstract:

    Abstract Persistent high-flux membranes were fabricated via kinetic and thermodynamic synergistic manipulation of Surface Segregation process. Poly (ether sulfone) (PES) was utilized as the bulk membrane material, poly (N-vinyl pyrrolidone-alt-maleic anhydride)-b-poly(styrene) (P(NVP-alt-MAH)-b-PS) with polyethylene glycol (PEG) was utilized as the precursor of Surface Segregation modifiers (SSMs). In casting solutions, the SSMs were in-situ synthesized through the alcoholysis reaction between the anhydride groups in P(NVP-alt-MAH)-b-PS and the hydroxyl groups in PEG, and then the membranes were fabricated with the non-solvent induced phase separation of PES and the Surface Segregation of the SSMs. The high mole ratio of hydrophilic/hydrophobic segments and adjustable crosslinking degree of the SSMs afforded the sufficient Surface enrichment of the hydrophilic segments in the SSMs, as a result, the coverage of PEG segments on the membrane Surfaces reached as high as 40.0 at%. Meanwhile, the strong interactions between the SSMs and PES and the high molecular weight of the SSMs afforded the durable Surface enrichment of the SSMs, as a result, the water contact angle and the O/C ratio of the membrane Surfaces were nearly unchanged after scoured by water for 30 days. Moreover, the crosslinked SSMs interfered and delayed the solidification of PES, endowing the membranes with higher porosity and bigger pore sizes. Accordingly, the membranes displayed persistent high-flux of 230 Lm−2h−1bar−1 in ternary-circle ultrafiltration experiment.

  • antifouling high flux membranes via Surface Segregation and phase separation controlled by the synergy of hydrophobic and hydrogen bond interactions
    Journal of Membrane Science, 2016
    Co-Authors: Xiaochen Fan, Runnan Zhang, Yanan Liu, Lin Fan, Qi Zhang, Zhen Yang, Zhongyi Jiang
    Abstract:

    Abstract Poly (ether sulfone)/Polyvinyl formal ultrafiltration membranes (PES/PVFM membranes) were fabricated via the synergy of Surface Segregation and non-solvent induced phase separation (NIPS). PES was utilized as bulk membrane materials and PVFM was utilized as Surface Segregation modifiers (SSM). The phase separation of PES and the Surface Segregation behavior of PVFM were controlled by the hydrophobic and hydrogen bond interactions between PES and PVFM. On one hand, the strong interactions delayed the phase separation of PES and promoted the development of membrane pores, increasing the membrane fluxes remarkably. On the other hand, the strong interactions anchored hydrophilic PVFM on the membrane Surfaces, endowing the membranes durable antifouling performance. The hydrophobic interaction was estimated by Guerout-Elford-Ferry equation and the hydrogen bond interaction was confirmed by Fourier transform infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC). The structures of PES/PVFM membranes were characterized by scanning electron microscopy (SEM) and the gravimetric method. The Surface Segregation of PVFM was explored by X-ray photoelectron spectroscopy (XPS). The PES/PVFM membranes exhibited high water fluxes (up to 1000 Lm −2  h −1  bar −1 ), high flux recovery ratio (up to 98%) and stable hydrophilicity (unchanged after incubated in deionized water for 30 days).

  • manipulating the Segregation behavior of polyethylene glycol by hydrogen bonding interaction to endow ultrafiltration membranes with enhanced antifouling performance
    Journal of Membrane Science, 2016
    Co-Authors: Xiaochen Fan, Runnan Zhang, Yanan Liu, Xueting Zhao, Zhongyi Jiang
    Abstract:

    Surface grafting and Surface Segregation are two dominant methods for antifouling membrane fabrication. Polyethylene glycol (PEG) has been demonstrated as the most popular Surface modifier in Surface grafting method, but has been less utilized in Surface Segregation method. In this study, antifouling ultrafiltration membranes were prepared via the non-solvent induced phase separation (NIPS), using polyethersulfone (PES) as membrane matrix, PEG as both Surface modifier and pore forming agent, and m-trihydroxybenzene (MTB) as hydrogen bond donor, respectively. The hydrogen bonding interaction between PES and PEG mediated by MTB was verified by Raman spectra and FT-IR spectra analysis, and the Surface Segregation behavior of PEG manipulated by hydrogen bonding interaction was explored by water contact angle and X-ray photoelectron spectroscopy (XPS) analysis. The enhanced antifouling performance of PES/PEG–MTB ultrafiltration membranes was verified by the increased flux recovery ratio in fouling resistance experiment. Moreover, the residence stability of PEG on membrane Surface was confirmed by a long-term test of incubating membranes in deionized water. This study provided a novel and generic approach to fabricate antifouling ultrafiltration membranes by Surface Segregation method.

  • coordination enabled synergistic Surface Segregation for fabrication of multi defense mechanism membranes
    Journal of Materials Chemistry, 2015
    Co-Authors: Xueting Zhao, Runnan Zhang, Heng Dai, Zhongyi Jiang
    Abstract:

    The antifouling mechanism lies at the heart of a number of Surface-governed applications ranging from biomedical implants and devices, marine coatings, to membrane separations. However, the multi-defense mechanism has not been ingeniously employed to design and fabricate high-performance antifouling membranes. In this study, a coordination chemistry-enabled approach is explored to manipulate the synergistic Surface Segregation of amphiphilic copolymers and hydrophilic inorganic nanoparticles during the membrane formation process, thus constructing membrane Surfaces with an optimally integrated fouling-resistant mechanism and fouling-release mechanism. Moreover, the metal–organic coordination interaction ensures the stable coexistence of copolymers and inorganic nanoparticles on the membrane Surface, as well as the high mechanical strength of membranes. Consequently, the membranes display superior antifouling properties and long-term stability in oil/water emulsion separation.

Yasuhiro Shiraki - One of the best experts on this subject based on the ideXlab platform.

K Muraki - One of the best experts on this subject based on the ideXlab platform.