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Papers by Haik Jamgotchian

Research paper thumbnail of High anisotropic inserted dendritic growth during first stage of Zn monolayer deposition on Ag(111) substrate

Research paper thumbnail of Array Disorder, Pattern Selection and Local Dendritic Transition in Cellular Directional Solidification

Research paper thumbnail of Growth of Silicon Nano-ribbons on Ag(110): State of the Art

Springer Series in Materials Science, 2016

Research paper thumbnail of Organisation des réseaux bidimensionnels de cellules de solidification dirigée

Research paper thumbnail of Erratum to: Pattern selection during directional solidification

Journal of Crystal Growth

ABSTRACT

Research paper thumbnail of In-Situ &REALTIME Observation by Optical Methods of Cellular Directional Solidification of a Transparent Alloy in a Cylinder

Research paper thumbnail of A comprehensive analysis of the (R13xR13)R13.9{\deg} type II structure of silicene on Ag(111)

Research paper thumbnail of Dynamics of the Interfacial Shape during the Directional Solidification of a Succinonitrile-0.2 wt % Acetone Alloy in a Cylinder

Research paper thumbnail of In situ Characterisation of the Effect of Thermal and Thermosolutal Convection on Directional Solidification of Succinonitrile-Acetone Alloy

Research paper thumbnail of A comprehensive study of the (2R3x2R3)R30 structure of silicene on Ag(111)

The deposition of one silicon monolayer on Ag (111) provides a set of superstructures depending o... more The deposition of one silicon monolayer on Ag (111) provides a set of superstructures depending on growth experimental conditions. These superstructures are correlated to the epitaxy between the honeycomb structure of silicon (so called silicene) and the silver substrate. In this paper, we bring new experimental results, obtained by Scanning Tunneling Microscopy and by Low Energy Electron Diffraction, on the (2R3x2R3) R30 structure which is the most controversial one. A detailed analysis of these results allows us to propose a new atomic model of the silicene layer based on periodic arrangements of perfect areas of (2R3x2R3)R30 surrounded by defect areas. A generalization of this model explains the main controversies of this structure: deviation of the average direction, Moir\'e patterns, and apparent global disorder.

Research paper thumbnail of Effect of experimental procedure on pattern formation and array disorder in cellular solidification

Cellular arrays in Bridgman directional solidification of Pb-Tl are investigated. By using two di... more Cellular arrays in Bridgman directional solidification of Pb-Tl are investigated. By using two different experimental procedures, the response of the planar interface to a sudden change in pulling velocity is examined. It is shown that the final pattern characteristics (average wavelength, level of disorder) are independent of experimental conditions even if the system reaches its steady state by different transients.

Research paper thumbnail of Cellular structures in three-dimensional directional solidification: Simulation and analysis

Physical Review E, 1998

Page 1. Cellular structures in three-dimensional directional solidification: Simulation and analy... more Page 1. Cellular structures in three-dimensional directional solidification: Simulation and analysis K. Kassner,1 J.-M. Debierre,2 B. Billia,2 N. Noël,2 and H. Jamgotchian2 1Institut für Theoretische Physik, Otto-von-Guericke-Universität ...

Research paper thumbnail of Nonlinear Dynamics in Cellular Solidification in Presence of Defects

Interactive Dynamics of Convection and Solidification, 1992

Research paper thumbnail of Silicene on Ag(111) : domains and local defects of the observed superstructures

Journal of Physics: Conference Series, 2014

On Ag(111) substrate, the growth of a silicene layer (the equivalent of graphene for silicon) giv... more On Ag(111) substrate, the growth of a silicene layer (the equivalent of graphene for silicon) gives rise to four main superstructures due to the epitaxy between the silicene layer (honeycomb structure) and the Ag(111) substrate. Depending on both the substrate temperature and the deposition rate, the following superstructures were observed: (4 × 4),

Research paper thumbnail of Free growth and instability morphologies in directional melting of alloys

Physical review. E, Statistical, nonlinear, and soft matter physics, 2002

The dynamics of melting morphologies, namely, liquid droplets in the bulk solid and liquid dendri... more The dynamics of melting morphologies, namely, liquid droplets in the bulk solid and liquid dendrites due to morphological instability of the phase boundary, is observed in situ and in real time during directional melting of transparent succinonitrile-acetone alloys in a cylinder. Specific patterns are associated to grain boundaries. A model based on free growth but with time-dependent superheating is proposed for the lateral growth of the liquid inclusions. Contrary to what is largely believed, it is shown that free melting is not the mere reversal of free crystal growth, basically because solute diffusion is much lower in the solid, which imposes a boundary layer approach.

Research paper thumbnail of Localized microstructures induced by fluid flow in directional solidification

Physical review letters, Jan 15, 2001

The dynamical process of microstructure localization by multiscale interaction between instabilit... more The dynamical process of microstructure localization by multiscale interaction between instabilities is uncovered in directional solidification of transparent alloy. As predicted by Chen and Davis, morphological instability of the interface is observed at inward flow-stagnation regions of the cellular convective field. Depending on the driving force of fluid flow, focus-type and honeycomb-type localized patterns form in the initial transient of solidification, that then evolves with time. In the case of solute-driven flow, the analysis of the onset of thermosolutal convection in initial transient of solidification enables a complete understanding of the dynamics and of the localization of morphological instability.

Research paper thumbnail of Array of doublets: A branch of cellular solutions in directional solidification

Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics, 1993

In directional solidification of alloys, the interface pattern assumes a cellular structure, with... more In directional solidification of alloys, the interface pattern assumes a cellular structure, with a periodic array of cells, when the velocity is increased beyond the threshold of planar interface instability. A detailed experimental study in the succinonitrile-acetone system has revealed a branch of cellular structure in which the interface pattern consists of a periodic array of coupled cells or doublets.

Research paper thumbnail of Deposition of gold nanofeatures on silicon samples by field-induced deposition using a scanning tunneling microscope

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2005

ABSTRACT Gold islands of diameter as small as 15 nm and 6 nm high were deposited on a standard si... more ABSTRACT Gold islands of diameter as small as 15 nm and 6 nm high were deposited on a standard silicon (100) surface by field-induced deposition using a scanning tunneling microscope operating with Pt or W tips coated by a gold film. Gold atoms are transferred by applying to the sample negative voltage pulses of few volts in magnitude, and of some tens of microseconds in duration. The scanning tunneling microscope tip morphology and composition have been analyzed systematically by field-emission gun scanning electron microscope plus energy dispersive x-ray (EDX) microanalysis before and after its use for lithography. The deposits composition have also been analyzed by EDX. Finally, preliminary results on trials of direct bonding of microscopic contact leads are presented.

Research paper thumbnail of Unidirectional solidification of dilute PbBi alloys

Acta Metallurgica, 1981

ABSTRACT

Research paper thumbnail of Atomic structure of the () R 30° of silicene on Ag(111) surface

Journal of Physics: Conference Series, 2014

The deposition of one monolayer of silicon on a Ag(111) substrate induces the formation of silice... more The deposition of one monolayer of silicon on a Ag(111) substrate induces the formation of silicene structures exhibiting different ordered phases, including a (2 √ 3×2 √ 3)R30 • , a (4×4) and a ( √ 13× √ 13)R13.9 • superstructures. In this paper we focus on the (2 √ 3× √ 3)R30 • phase. Using a combination of scanning tunneling microscopy and LEED observations, we show that this phase corresponds to a 11 • rotation of the silicene sheet relative to the substrate orientation.

Research paper thumbnail of High anisotropic inserted dendritic growth during first stage of Zn monolayer deposition on Ag(111) substrate

Research paper thumbnail of Array Disorder, Pattern Selection and Local Dendritic Transition in Cellular Directional Solidification

Research paper thumbnail of Growth of Silicon Nano-ribbons on Ag(110): State of the Art

Springer Series in Materials Science, 2016

Research paper thumbnail of Organisation des réseaux bidimensionnels de cellules de solidification dirigée

Research paper thumbnail of Erratum to: Pattern selection during directional solidification

Journal of Crystal Growth

ABSTRACT

Research paper thumbnail of In-Situ &REALTIME Observation by Optical Methods of Cellular Directional Solidification of a Transparent Alloy in a Cylinder

Research paper thumbnail of A comprehensive analysis of the (R13xR13)R13.9{\deg} type II structure of silicene on Ag(111)

Research paper thumbnail of Dynamics of the Interfacial Shape during the Directional Solidification of a Succinonitrile-0.2 wt % Acetone Alloy in a Cylinder

Research paper thumbnail of In situ Characterisation of the Effect of Thermal and Thermosolutal Convection on Directional Solidification of Succinonitrile-Acetone Alloy

Research paper thumbnail of A comprehensive study of the (2R3x2R3)R30 structure of silicene on Ag(111)

The deposition of one silicon monolayer on Ag (111) provides a set of superstructures depending o... more The deposition of one silicon monolayer on Ag (111) provides a set of superstructures depending on growth experimental conditions. These superstructures are correlated to the epitaxy between the honeycomb structure of silicon (so called silicene) and the silver substrate. In this paper, we bring new experimental results, obtained by Scanning Tunneling Microscopy and by Low Energy Electron Diffraction, on the (2R3x2R3) R30 structure which is the most controversial one. A detailed analysis of these results allows us to propose a new atomic model of the silicene layer based on periodic arrangements of perfect areas of (2R3x2R3)R30 surrounded by defect areas. A generalization of this model explains the main controversies of this structure: deviation of the average direction, Moir\'e patterns, and apparent global disorder.

Research paper thumbnail of Effect of experimental procedure on pattern formation and array disorder in cellular solidification

Cellular arrays in Bridgman directional solidification of Pb-Tl are investigated. By using two di... more Cellular arrays in Bridgman directional solidification of Pb-Tl are investigated. By using two different experimental procedures, the response of the planar interface to a sudden change in pulling velocity is examined. It is shown that the final pattern characteristics (average wavelength, level of disorder) are independent of experimental conditions even if the system reaches its steady state by different transients.

Research paper thumbnail of Cellular structures in three-dimensional directional solidification: Simulation and analysis

Physical Review E, 1998

Page 1. Cellular structures in three-dimensional directional solidification: Simulation and analy... more Page 1. Cellular structures in three-dimensional directional solidification: Simulation and analysis K. Kassner,1 J.-M. Debierre,2 B. Billia,2 N. Noël,2 and H. Jamgotchian2 1Institut für Theoretische Physik, Otto-von-Guericke-Universität ...

Research paper thumbnail of Nonlinear Dynamics in Cellular Solidification in Presence of Defects

Interactive Dynamics of Convection and Solidification, 1992

Research paper thumbnail of Silicene on Ag(111) : domains and local defects of the observed superstructures

Journal of Physics: Conference Series, 2014

On Ag(111) substrate, the growth of a silicene layer (the equivalent of graphene for silicon) giv... more On Ag(111) substrate, the growth of a silicene layer (the equivalent of graphene for silicon) gives rise to four main superstructures due to the epitaxy between the silicene layer (honeycomb structure) and the Ag(111) substrate. Depending on both the substrate temperature and the deposition rate, the following superstructures were observed: (4 × 4),

Research paper thumbnail of Free growth and instability morphologies in directional melting of alloys

Physical review. E, Statistical, nonlinear, and soft matter physics, 2002

The dynamics of melting morphologies, namely, liquid droplets in the bulk solid and liquid dendri... more The dynamics of melting morphologies, namely, liquid droplets in the bulk solid and liquid dendrites due to morphological instability of the phase boundary, is observed in situ and in real time during directional melting of transparent succinonitrile-acetone alloys in a cylinder. Specific patterns are associated to grain boundaries. A model based on free growth but with time-dependent superheating is proposed for the lateral growth of the liquid inclusions. Contrary to what is largely believed, it is shown that free melting is not the mere reversal of free crystal growth, basically because solute diffusion is much lower in the solid, which imposes a boundary layer approach.

Research paper thumbnail of Localized microstructures induced by fluid flow in directional solidification

Physical review letters, Jan 15, 2001

The dynamical process of microstructure localization by multiscale interaction between instabilit... more The dynamical process of microstructure localization by multiscale interaction between instabilities is uncovered in directional solidification of transparent alloy. As predicted by Chen and Davis, morphological instability of the interface is observed at inward flow-stagnation regions of the cellular convective field. Depending on the driving force of fluid flow, focus-type and honeycomb-type localized patterns form in the initial transient of solidification, that then evolves with time. In the case of solute-driven flow, the analysis of the onset of thermosolutal convection in initial transient of solidification enables a complete understanding of the dynamics and of the localization of morphological instability.

Research paper thumbnail of Array of doublets: A branch of cellular solutions in directional solidification

Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics, 1993

In directional solidification of alloys, the interface pattern assumes a cellular structure, with... more In directional solidification of alloys, the interface pattern assumes a cellular structure, with a periodic array of cells, when the velocity is increased beyond the threshold of planar interface instability. A detailed experimental study in the succinonitrile-acetone system has revealed a branch of cellular structure in which the interface pattern consists of a periodic array of coupled cells or doublets.

Research paper thumbnail of Deposition of gold nanofeatures on silicon samples by field-induced deposition using a scanning tunneling microscope

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2005

ABSTRACT Gold islands of diameter as small as 15 nm and 6 nm high were deposited on a standard si... more ABSTRACT Gold islands of diameter as small as 15 nm and 6 nm high were deposited on a standard silicon (100) surface by field-induced deposition using a scanning tunneling microscope operating with Pt or W tips coated by a gold film. Gold atoms are transferred by applying to the sample negative voltage pulses of few volts in magnitude, and of some tens of microseconds in duration. The scanning tunneling microscope tip morphology and composition have been analyzed systematically by field-emission gun scanning electron microscope plus energy dispersive x-ray (EDX) microanalysis before and after its use for lithography. The deposits composition have also been analyzed by EDX. Finally, preliminary results on trials of direct bonding of microscopic contact leads are presented.

Research paper thumbnail of Unidirectional solidification of dilute PbBi alloys

Acta Metallurgica, 1981

ABSTRACT

Research paper thumbnail of Atomic structure of the () R 30° of silicene on Ag(111) surface

Journal of Physics: Conference Series, 2014

The deposition of one monolayer of silicon on a Ag(111) substrate induces the formation of silice... more The deposition of one monolayer of silicon on a Ag(111) substrate induces the formation of silicene structures exhibiting different ordered phases, including a (2 √ 3×2 √ 3)R30 • , a (4×4) and a ( √ 13× √ 13)R13.9 • superstructures. In this paper we focus on the (2 √ 3× √ 3)R30 • phase. Using a combination of scanning tunneling microscopy and LEED observations, we show that this phase corresponds to a 11 • rotation of the silicene sheet relative to the substrate orientation.