Articles de journaux |
A. Montiel, T. Nguyen, C. Rountree, V. Geertsen, P. Guenoun, D. Bonamy Effect of architectural disorder on the elastic response in 2D microlattices Article de journal Forthcoming Physical Review B, Forthcoming. BibTeX @article{Montiel0000,
title = {Effect of architectural disorder on the elastic response in 2D microlattices},
author = {A. Montiel, T. Nguyen, C. Rountree, V. Geertsen, P. Guenoun, D. Bonamy},
editor = {American Physical Society},
year = {2021},
date = {2021-00-00},
journal = {Physical Review B},
keywords = {},
pubstate = {forthcoming},
tppubtype = {article}
}
|
T. Nguyen; D. Bonamy Size effects on the fracture energy of brittle materials Article de journal Forthcoming Forthcoming. BibTeX @article{Nguyen2021b,
title = {Size effects on the fracture energy of brittle materials},
author = {T. Nguyen and D. Bonamy},
year = {2021},
date = {2021-00-00},
keywords = {},
pubstate = {forthcoming},
tppubtype = {article}
}
|
T. Nguyen; D. Bonamy Role of the Crystal Lattice Structure in Predicting Fracture Toughness Article de journal Physical Review Letter, 123 , p. 205503, 2019. Résumé | Liens | BibTeX @article{Nguyen2019,
title = {Role of the Crystal Lattice Structure in Predicting Fracture Toughness},
author = {T. Nguyen and D. Bonamy},
editor = {American Physical Society},
url = {https://www.devinci.fr/physrevlett_19_nguyenbonamy-2/},
doi = {https://doi.org/10.1103/PhysRevLett.123.205503},
year = {2019},
date = {2019-11-15},
journal = {Physical Review Letter},
volume = {123},
pages = {205503},
abstract = {We examine the atomistic scale dependence of a material’s resistance to failure by numerical simulations and analytical analysis in electrical analogs of brittle crystals. We show that fracture toughness depends on the lattice geometry in a way incompatible with Griffith’s relationship between fracture and free surface energy. Its value finds its origin in the matching between the continuum displacement field at the engineering scale, and the discrete nature of solids at the atomic scale. The generic asymptotic form taken by this field near the crack tip provides a solution for this matching, and subsequently a way to predict toughness from the atomistic parameters with application to graphene.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We examine the atomistic scale dependence of a material’s resistance to failure by numerical simulations and analytical analysis in electrical analogs of brittle crystals. We show that fracture toughness depends on the lattice geometry in a way incompatible with Griffith’s relationship between fracture and free surface energy. Its value finds its origin in the matching between the continuum displacement field at the engineering scale, and the discrete nature of solids at the atomic scale. The generic asymptotic form taken by this field near the crack tip provides a solution for this matching, and subsequently a way to predict toughness from the atomistic parameters with application to graphene. |
T. Nguyen; D. Bonamy Supplementary Material for "Role of the crystal lattice structure in the selection of fracture toughness" Article de journal Physical Review Letter, 123 , 2019. Liens | BibTeX @article{Nguyen2019b,
title = {Supplementary Material for "Role of the crystal lattice structure in the selection of fracture toughness"},
author = {T. Nguyen and D. Bonamy},
editor = {American Physical Society},
url = {https://www.devinci.fr/prl-thuy-suppmat-v2/},
doi = {PhysRevLett.123.205503},
year = {2019},
date = {2019-11-15},
journal = {Physical Review Letter},
volume = {123},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
|
V.H. Nguyen; T. Nguyen Approximating the asymmetric profitable tour Article de journal International Journal of Mathematics in Operational Research, 4 (3), p. 294, 2012. Liens | BibTeX @article{Nguyen2012,
title = {Approximating the asymmetric profitable tour},
author = {V.H. Nguyen and T. Nguyen},
editor = {Inderscience},
url = {https://www.inderscience.com/info/inarticle.php?artid=46689},
doi = { DOI: 10.1504/IJMOR.2012.046689},
year = {2012},
date = {2012-05-02},
journal = {International Journal of Mathematics in Operational Research},
volume = {4},
number = {3},
pages = {294},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
|
V.H. Nguyen; T. Nguyen Approximating the asymmetric profitable tour Article de journal Electronic Notes in Discrete Mathematics, 36 , p. 907, 2010. Résumé | Liens | BibTeX @article{Nguyen2010b,
title = {Approximating the asymmetric profitable tour},
author = {V.H. Nguyen and T. Nguyen},
editor = {Elsevier},
url = {https://www.devinci.fr/1-s2-0-s1571065310001162-main/},
doi = {https://doi.org/10.1016/j.endm.2010.05.115},
year = {2010},
date = {2010-08-01},
journal = {Electronic Notes in Discrete Mathematics},
volume = {36},
pages = {907},
abstract = {We study the version of the asymmetric prize collecting traveling salesman problem, where the objective is to find a directed tour that visits a subset of vertices such that the length of the tour plus the sum of penalties associated with vertices not in the tour is as small as possible. In [Dell'Amico, M., Maffioli, F. and Väbrand P.: On Prize-collecting Tours and the Asymmetric Travelling Salesman Problem, Int. Trans. Opl Res., Vol. 2, 297–308 (1995)], the authors defined it as the Profitable Tour Problem (PTP). We present an (1 + ⌈log(n)⌉)-approximation algorithm for the asymmetric PTP with n is the vertex number. The algorithm that is based on Frieze et al.'s heuristic for the asymmetric traveling salesman problem as well as a method to round fractional solutions of a linear programming relaxation to integers (feasible solution for the original problem), represents a directed version of the Bienstock et al.'s [Bienstock, D., Goemans, M.X., Simchi-Levi, D. and Williamson, D.P.: A note on the prize collecting traveling salesman problem, Math. Prog., Vol. 59, 413–420 (1993)] algorithm for the symmetric PTP.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We study the version of the asymmetric prize collecting traveling salesman problem, where the objective is to find a directed tour that visits a subset of vertices such that the length of the tour plus the sum of penalties associated with vertices not in the tour is as small as possible. In [Dell'Amico, M., Maffioli, F. and Väbrand P.: On Prize-collecting Tours and the Asymmetric Travelling Salesman Problem, Int. Trans. Opl Res., Vol. 2, 297–308 (1995)], the authors defined it as the Profitable Tour Problem (PTP). We present an (1 + ⌈log(n)⌉)-approximation algorithm for the asymmetric PTP with n is the vertex number. The algorithm that is based on Frieze et al.'s heuristic for the asymmetric traveling salesman problem as well as a method to round fractional solutions of a linear programming relaxation to integers (feasible solution for the original problem), represents a directed version of the Bienstock et al.'s [Bienstock, D., Goemans, M.X., Simchi-Levi, D. and Williamson, D.P.: A note on the prize collecting traveling salesman problem, Math. Prog., Vol. 59, 413–420 (1993)] algorithm for the symmetric PTP. |
T. Nguyen, D. Bonamy, L. Phan Van, J. Cousty; L. Barbier Scaling and universality in the kinetic smoothening of interfaces: Application to the analysis of the relaxation of rough vicinal steps of an oxide surface Article de journal Europhysics Letters, 89 (6), p. 60005, 2010. Résumé | Liens | BibTeX @article{Nguyen2010,
title = {Scaling and universality in the kinetic smoothening of interfaces: Application to the analysis of the relaxation of rough vicinal steps of an oxide surface},
author = {T. Nguyen, D. Bonamy, L. Phan Van, J. Cousty and L. Barbier},
editor = {EDP Sciences},
url = {https://www.devinci.fr/epl_10_thuynguyen-2/},
doi = { https://doi.org/10.1209/0295-5075/89/60005 },
year = {2010},
date = {2010-04-19},
journal = {Europhysics Letters},
volume = {89},
number = {6},
pages = {60005},
abstract = {Relaxation of initially out-of-equilibrium rough interfaces in the presence of thermal noise is investigated using Langevin formalism. During thermal equilibration towards the well-known roughening regime, three scaling regimes observed over three successive ranges of length-scales are evidenced: thermal roughening (late stage) at small scales, transient smoothening at intermediate scales and remnant of the initial conditions at large scales. A generalization of the Family-Vicsek scaling is found for the smoothening regime. This approach allows interpreting a series of AFM images of sapphire surfaces showing the thermal evolution of initially rough step edges.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Relaxation of initially out-of-equilibrium rough interfaces in the presence of thermal noise is investigated using Langevin formalism. During thermal equilibration towards the well-known roughening regime, three scaling regimes observed over three successive ranges of length-scales are evidenced: thermal roughening (late stage) at small scales, transient smoothening at intermediate scales and remnant of the initial conditions at large scales. A generalization of the Family-Vicsek scaling is found for the smoothening regime. This approach allows interpreting a series of AFM images of sapphire surfaces showing the thermal evolution of initially rough step edges. |
T. Nguyen, D. Bonamy, L. Phan Van, J. Cousty; L. Barbier Coarsening of two-dimensional Al2O3 islands on vicinal (1-102) sapphire surfaces Article de journal Surface Science, 602 (21), p. 3232-3238, 2008. Résumé | Liens | BibTeX @article{Nguyen2008,
title = {Coarsening of two-dimensional Al2O3 islands on vicinal (1-102) sapphire surfaces},
author = {T. Nguyen, D. Bonamy, L. Phan Van, J. Cousty and L. Barbier},
editor = {Elvier},
doi = {https://doi.org/10.1016/j.susc.2008.08.022},
year = {2008},
date = {2008-11-01},
journal = {Surface Science},
volume = {602},
number = {21},
pages = { 3232-3238},
abstract = {The evolution of two-dimensional (2D) islands which result from a chemo-mechanical polishing of vicinal (1, −1, 0, 2) sapphire surfaces was explored by atomic force microscopy (AFM) after annealing in air. The evolution of the surface morphology is followed after isothermal annealing (1173 K) for duration varying from 1 h to 53 h and isochronal annealing at temperatures between 1023 K < T < 1253 K. Statistical analysis of the AFM images gives evidence that an anisotropic Ostwald ripening governs the evolution of the 2D island distribution. The activation energy for mass transport on the terrace is found to be 1.3 ± 0.1 eV.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The evolution of two-dimensional (2D) islands which result from a chemo-mechanical polishing of vicinal (1, −1, 0, 2) sapphire surfaces was explored by atomic force microscopy (AFM) after annealing in air. The evolution of the surface morphology is followed after isothermal annealing (1173 K) for duration varying from 1 h to 53 h and isochronal annealing at temperatures between 1023 K < T < 1253 K. Statistical analysis of the AFM images gives evidence that an anisotropic Ostwald ripening governs the evolution of the 2D island distribution. The activation energy for mass transport on the terrace is found to be 1.3 ± 0.1 eV. |
Conférences |
T. Nguyen; D. Bonamy Lattice trapping and fracture toughness selection in brittle crystals 5500 - 5599 Conférence 25th International Congress of Theoretical and Applied Mechanics, Milan-Italy 2021. Résumé | BibTeX @conference{Nguyen2021,
title = {Lattice trapping and fracture toughness selection in brittle crystals },
author = {T. Nguyen and D. Bonamy},
editor = {25th International Congress of Theoretical and Applied Mechanics},
year = {2021},
date = {2021-08-22},
organization = {25th International Congress of Theoretical and Applied Mechanics, Milan-Italy},
abstract = {Predicting the resistance-to-failure from the solid structure at the atomistic scale remains unsolved, even in the simplest situations of perfectly brittle fracture. By examining numerically crack growth in electrical analogues of brittle crystals, we shed a new light on this question: Fracture toughness is found to be significantly higher than expected from Griffith’s relationship between fracture and specific surface energy. This discrepancy finds its origin in the matching between the continuum displacement field at the engineering scale and the discrete lattice of solids at the atomic scale. We will show how to use the specific asymptotic form taken by this field near crack tip to infer this matching, and subsequently to predict toughness from the atomistic parameters. The implications will be discussed. },
keywords = {},
pubstate = {published},
tppubtype = {conference}
}
Predicting the resistance-to-failure from the solid structure at the atomistic scale remains unsolved, even in the simplest situations of perfectly brittle fracture. By examining numerically crack growth in electrical analogues of brittle crystals, we shed a new light on this question: Fracture toughness is found to be significantly higher than expected from Griffith’s relationship between fracture and specific surface energy. This discrepancy finds its origin in the matching between the continuum displacement field at the engineering scale and the discrete lattice of solids at the atomic scale. We will show how to use the specific asymptotic form taken by this field near crack tip to infer this matching, and subsequently to predict toughness from the atomistic parameters. The implications will be discussed. |
A. Montiel, T. Nguyen, M Perchelet, V. Geertsen, C. Rountree, P. Guenoun; D. Bonamy Mechanical and fracture behaviour of microlattice-based metamaterial with disordered architecture 5500 - 5599 Conférence 25th International Congress of Theoretical and Applied Mechanics, Milan - Italy 2021. Résumé | BibTeX @conference{Montiel2021,
title = {Mechanical and fracture behaviour of microlattice-based metamaterial with disordered architecture},
author = {A. Montiel, T. Nguyen, M Perchelet, V. Geertsen, C. Rountree, P. Guenoun and D. Bonamy
},
editor = {25th International Congress of Theoretical and Applied Mechanics (25th ICTAM)},
year = {2021},
date = {2021-08-21},
organization = {25th International Congress of Theoretical and Applied Mechanics, Milan - Italy},
abstract = {Microlattice based metamaterials made of periodically arranged hollow microtubes appear as highly promising materials; they
both combine ultra-low density and sufficient stiffness and mechanical strength to envisage their use as structure material, in the aeronautical
industry for instance. Still, until now, most studies have considered periodically ordered architectures. Here, we explored amorphous
architectures and analysed how the disorder amount plays on the mechanical and failure properties. The presented study relies on both
numerical simulations using Timoshenko beam model and experiments performed on 3D-printed samples, the architecture of which mimics
that of the simulated samples.},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}
Microlattice based metamaterials made of periodically arranged hollow microtubes appear as highly promising materials; they
both combine ultra-low density and sufficient stiffness and mechanical strength to envisage their use as structure material, in the aeronautical
industry for instance. Still, until now, most studies have considered periodically ordered architectures. Here, we explored amorphous
architectures and analysed how the disorder amount plays on the mechanical and failure properties. The presented study relies on both
numerical simulations using Timoshenko beam model and experiments performed on 3D-printed samples, the architecture of which mimics
that of the simulated samples. |
V.H. Nguyen; T. Nguyen Approximating the asymmetric profitable tour 5500 - 5599 Conférence International Symposium on Combinatorial Optimization, Hammamet - Tunisia 2010. BibTeX @conference{Nguyen2010c,
title = {Approximating the asymmetric profitable tour},
author = {V.H. Nguyen and T. Nguyen},
editor = {International Symposium on Combinatorial Optimization},
year = {2010},
date = {2010-03-08},
organization = {International Symposium on Combinatorial Optimization, Hammamet - Tunisia},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}
|
T. Nguyen, D. Bonamy, L. Pham Van, L. Barbier; J. Cousty. Evolution morphologique d’ilots bidimensionnels d’alumine sur une surface vicinale de saphir proche de (1,-1,0, 2) lors de recuits à l’air: une étude par AFM, 5500 - 5599 Conférence Forum de microscopes à sondes locales, La Londe les Maures 2008. Résumé | BibTeX @conference{Nguyen2008b,
title = {Evolution morphologique d’ilots bidimensionnels d’alumine sur une surface vicinale de saphir proche de (1,-1,0, 2) lors de recuits à l’air: une étude par AFM,},
author = {T. Nguyen, D. Bonamy, L. Pham Van, L. Barbier and J. Cousty.},
editor = {Forum de microscopes à sondes locales, La Londe les Maures },
year = {2008},
date = {2008-03-17},
organization = {Forum de microscopes à sondes locales, La Londe les Maures },
abstract = {La Londe les Maures - Forum de microscopes à sondes locales - Evolution
morphologique d’ilots bidimensionnels d’alumine sur une surface vicinale de saphir proche de
(1,-1,0, 2) lors de recuits à l’air: une étude par AFM, T. Nguyen, D. Bonamy, L. Pham Van, L.
Barbier, J. Cousty.},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}
La Londe les Maures - Forum de microscopes à sondes locales - Evolution
morphologique d’ilots bidimensionnels d’alumine sur une surface vicinale de saphir proche de
(1,-1,0, 2) lors de recuits à l’air: une étude par AFM, T. Nguyen, D. Bonamy, L. Pham Van, L.
Barbier, J. Cousty. |
T. Nguyen, D. Bonamy, L. Pham Van, J. Cousty; L. Barbier Thermal smoothing of monoatomic step edges of a (1-102) vicinal surface of sapphire 5500 - 5599 Conférence 13th International Conference on Surface Science (ICSS-13) & International Conference on Nano Science and Technology (ICN+T), Stockholm-Sweden 2007. BibTeX @conference{,
title = {Thermal smoothing of monoatomic step edges of a (1-102) vicinal surface of sapphire},
author = {T. Nguyen, D. Bonamy, L. Pham Van, J. Cousty and L. Barbier
},
year = {2007},
date = {2007-07-02},
journal = {Physical Review B},
organization = {13th International Conference on Surface Science (ICSS-13) & International Conference on Nano Science and Technology (ICN+T), Stockholm-Sweden},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}
|
T. Nguyen, L. Pham Van; J.Cousty. NC-AFM: Bruits de phase d’AFM et imagerie d’isolants 5500 - 5599 Conférence Forum de microscopes à sondes locales, Autrans 2006. BibTeX @conference{Nguyen2006,
title = {NC-AFM: Bruits de phase d’AFM et imagerie d’isolants},
author = { T. Nguyen, L. Pham Van and J.Cousty.},
year = {2006},
date = {2006-03-27},
organization = {Forum de microscopes à sondes locales, Autrans },
keywords = {},
pubstate = {published},
tppubtype = {conference}
}
|
L. Pham Van, T. Nguyen, L. Manzon, C. Lubin; J. Cousty Charge sur isolants : deux approches complémentaires 5500 - 5599 Conférence Forum de microscopes à sondes locales, Anglet 2005. Résumé | BibTeX @conference{Van2005,
title = {Charge sur isolants : deux approches complémentaires},
author = { L. Pham Van, T. Nguyen, L. Manzon, C. Lubin and J. Cousty},
year = {2005},
date = {2005-03-28},
organization = {Forum de microscopes à sondes locales, Anglet},
abstract = {Anglet 2005 - Affiche - Forum de microscopes à sondes locales, Charge sur isolants : deux
approches complémentaires, L. Pham Van, T. Nguyen, L. Manzon, C. Lubin, J. Cousty.},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}
Anglet 2005 - Affiche - Forum de microscopes à sondes locales, Charge sur isolants : deux
approches complémentaires, L. Pham Van, T. Nguyen, L. Manzon, C. Lubin, J. Cousty. |
inproceedings |
T. Nguyen; D. Bonamy Lattice trapping and fracture toughness selection in brittle crystals Inproceedings ICTAM 22-27 August 2021, Milano Italy (Ed.): 2021. Liens | BibTeX @inproceedings{ICTAM2021,
title = {Lattice trapping and fracture toughness selection in brittle crystals},
author = {T. Nguyen and D. Bonamy},
editor = {ICTAM, 22-27 August 2021, Milano, Italy},
url = {https://www.devinci.fr/ictam2020_bonamynguyen/},
year = {2021},
date = {2021-08-22},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
|
En ligne |
T. Nguyen; D. Bonamy Breaking news : les solides fragiles le sont moins que prévu ! En ligne Faits Marquants du SPEC, CEA (Ed.): 2019. Liens | BibTeX @online{Nguyen2019c,
title = {Breaking news : les solides fragiles le sont moins que prévu !},
author = {T. Nguyen and D. Bonamy},
editor = {Faits Marquants du SPEC, CEA },
url = {http://iramis.cea.fr/spec/Phocea/Vie_des_labos/Ast/ast.php?t=fait_marquant&id_ast=3180
},
year = {2019},
date = {2019-12-13},
keywords = {},
pubstate = {published},
tppubtype = {online}
}
|
Thèses |
T. Nguyen Structure et cinétique de mise à l’équilibre d’une surface vicinale (1 -1 0 2) de saphir : étude par Microscope à Force Atomique Thèse de doctorat Université Paris Saclay , 2008. Résumé | Liens | BibTeX @phdthesis{Nguyen2008c,
title = {Structure et cinétique de mise à l’équilibre d’une surface vicinale (1 -1 0 2) de saphir : étude par Microscope à Force Atomique},
author = {T. Nguyen},
editor = {Université Paris Saclay},
url = {https://www.theses.fr/2008PA112346
},
year = {2008},
date = {2008-11-13},
school = {Université Paris Saclay },
abstract = {Les oxydes métalliques sont couramment mis en œuvre dans des secteurs innovants comme les nanotechnologies, la microélectronique, la catalyse hétérogène et le stockage longue durée de déchets nucléaires. Pour toutes ces applications, la présence de défauts superficiels peut affecter certaines propriétés physico-chimiques de la surface de ces oxydes. La cinétique de mise à l'équilibre de surfaces vicinales proches du plan (1-102) d’un cristal de saphir initialement rugueuses a été étudiée par microscopie à force atomique (AFM). Cette rugosité, due à la préparation de l’échantillon, se traduit par une grande densité de défauts. Lors de recuits à l’air, qui conservent la stœchiométrie superficielle, ces défauts forment des ilots bidimensionnels au voisinage des bords de marche monoatomique. L’évolution morphologique des ilots et des bords de marche est analysée après recuits à l'air à différents temps et températures. Deux régimes de cinétique sont identifiés. Le premier, associé à des recuits isochrones (une heure) pour des températures allant de 973 K à 1173 K ou à des recuits isothermes (1173 K) pour des durées allant jusqu’à 53 heures, correspond au processus de mûrissement d'Ostwald des ilots contrôlé par une diffusion anisotrope sur les terrasses avec une énergie d'activation de 1. 3 ± 0. 1 eV. Le second régime, étudié après la disparition des îlots, concerne la gamme de température supérieure (1273 K < T < 1473 K) ou à plus longue durée de recuit. Un bon accord entre les résultats expérimentaux, un modèle théorique basé sur l'équation de Langevin et des simulations numériques montre que le lissage du profil des marches est gouverné par l'émission d'atomes à partir du bord de marche. Les atomes issus de la marche diffusent sur la terrasse voisine pour se piéger sur une des marches qui la bordent. Les paramètres atomistiques, comme l’énergie d’activation, peuvent également être déduits. Cette étude statistique originale de l'évolution morphologique d'une surface hors d'équilibre démontre qu'il est possible d'accéder, à partir d’images AFM de dimensions micrométriques, au processus de transport de matières et aux paramètres atomistiques associés. Enfin, la méthodologie développée est généralisable à l'analyse non seulement des marches stables de toutes surfaces cristallines quelle qu’en soit la rugosité initiale mais elle peut être utilisée pour l'analyse du profil d'une interface quelconque. },
keywords = {},
pubstate = {published},
tppubtype = {phdthesis}
}
Les oxydes métalliques sont couramment mis en œuvre dans des secteurs innovants comme les nanotechnologies, la microélectronique, la catalyse hétérogène et le stockage longue durée de déchets nucléaires. Pour toutes ces applications, la présence de défauts superficiels peut affecter certaines propriétés physico-chimiques de la surface de ces oxydes. La cinétique de mise à l'équilibre de surfaces vicinales proches du plan (1-102) d’un cristal de saphir initialement rugueuses a été étudiée par microscopie à force atomique (AFM). Cette rugosité, due à la préparation de l’échantillon, se traduit par une grande densité de défauts. Lors de recuits à l’air, qui conservent la stœchiométrie superficielle, ces défauts forment des ilots bidimensionnels au voisinage des bords de marche monoatomique. L’évolution morphologique des ilots et des bords de marche est analysée après recuits à l'air à différents temps et températures. Deux régimes de cinétique sont identifiés. Le premier, associé à des recuits isochrones (une heure) pour des températures allant de 973 K à 1173 K ou à des recuits isothermes (1173 K) pour des durées allant jusqu’à 53 heures, correspond au processus de mûrissement d'Ostwald des ilots contrôlé par une diffusion anisotrope sur les terrasses avec une énergie d'activation de 1. 3 ± 0. 1 eV. Le second régime, étudié après la disparition des îlots, concerne la gamme de température supérieure (1273 K < T < 1473 K) ou à plus longue durée de recuit. Un bon accord entre les résultats expérimentaux, un modèle théorique basé sur l'équation de Langevin et des simulations numériques montre que le lissage du profil des marches est gouverné par l'émission d'atomes à partir du bord de marche. Les atomes issus de la marche diffusent sur la terrasse voisine pour se piéger sur une des marches qui la bordent. Les paramètres atomistiques, comme l’énergie d’activation, peuvent également être déduits. Cette étude statistique originale de l'évolution morphologique d'une surface hors d'équilibre démontre qu'il est possible d'accéder, à partir d’images AFM de dimensions micrométriques, au processus de transport de matières et aux paramètres atomistiques associés. Enfin, la méthodologie développée est généralisable à l'analyse non seulement des marches stables de toutes surfaces cristallines quelle qu’en soit la rugosité initiale mais elle peut être utilisée pour l'analyse du profil d'une interface quelconque. |
