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Featured researches published by Thierry Duffar.


Journal of Crystal Growth | 1993

Wetting of III–V melts on crucible materials

I. Harter; P. Dusserre; Thierry Duffar; J.Ph. Nabot; N. Eustathopoulos

Abstract The measurement of the wetting angle of GaSb and InSb melts on C, BN, AIN, Al 2 O 3 and SiO 2 substrates by the sessile drop method under static vacuum is described and discussed. The surface tension and the work of adhesion are calculated. Finally, the results are compared with published data and with the predictions of theoretical models.


Journal of Crystal Growth | 1997

Theoretical model of crystal growth shaping process

V.A. Tatarchenko; V.S. Uspenski; E.V. Tatarchenko; J.Ph. Nabot; Thierry Duffar; B. Roux

Abstract A theoretical investigation of the crystal growth shaping process is carried out on the basis of the dynamic stability concept. The capillary dynamic stability of shaped crystal growth processes for various forms of the liquid menisci is analyzed using the mathematical model of the phenomena in the axisymmetric case. The catching boundary condition of the capillary boundary problem is considered and the limits of its application for shaped crystal growth modeling are discussed. The static stability of a liquid free surface is taken into account by means of the Jacobi equation analysis. The result is that a large number of menisci having drop-like shapes are statically unstable. A few new non-traditional liquid meniscus shapes (e.g., bubbles and related shapes) are proposed for the case of a catching boundary condition.


Journal of Crystal Growth | 1997

Full encapsulation by molten salts during the Bridgman growth process

Thierry Duffar; J.M. Gourbil; P. Boiton; Pierre Dusserre; N. Eustathopoulos

Abstract Full encapsulation of liquid semiconductors during Bridgman growth helps to improve the crystal quality by decreasing the nucleation of grains and the dislocation density. An experimental and theoretical study has been undertaken in order to better understand the phenomena and to determine the necessary conditions to be achieved. In the case of the LiClKCl encapsulant in silica crucibles, surface energy calculations predict a stable salt layer between the molten semiconductor and the crucible. For GaAs growth with B 2 O 3 encapsulant, surface energies are not strong enough and it is shown that the oxide layer is due to the high viscosity of the encapsulant which prevents it flowing upward. It is then mandatory to have a good wetting of the crucible walls by the boron oxide before the melting of the semiconductor.


Journal of Crystal Growth | 1997

Some features of two commercial softwares for the modeling of bulk crystal growth processes

J.L. Santailler; Thierry Duffar; F. Théodore; P. Boiton; C. Barat; B. Angelier; N. Giacometti; Pierre Dusserre; J.P. Nabot

Two commercial codes, FIDAP and MARC, have been used to model a number of crystal growth processes in collaboration with industrial and research teams. Examples of global and local simulations in the field of heat transfer, hydrodynamics, chemistry and mechanics are given and the results are compared to experimental measurements, with good agreement as a rule. This establishes that such codes can be used to help improve crystal growth processes, while full global transient models still belong to software specifically written in order to model crystal growth. Emphasis is put on the necessity to validate the numerical results by comparison with experiments and to have a clear understanding of the physical laws hidden behind the software.


Journal of Crystal Growth | 1999

Effect of crucible–sample adhesion on grain germination

Thierry Duffar; Pierre Dusserre; N. Giacometti; P. Boiton; J.P. Nabot; N. Eustathopoulos

Solid-liquid interface demarcations have been performed during the growth of GaSb and Ge samples by the vertical Bridgman method. The crucibles were made of boron nitride, silica or carbon based materials. Subsequent metallographies in a plane containing the sample axis show that the interface is distorted on a distance of about 100 μm close to the crucible wall. The angle of the interface line with the crucible, measured on the solid side, ranges between 25° for GaSb/BN to 120° for Ge/SiO 2 . These measures are compared to the experimental observation that parasitic grain nucleation has a high probability of occurrence when BN crucibles are used and a rather low one in the case of silica crucibles. These results are in qualitative agreement with the theory of nucleation on homogeneous or heterogeneous substrates.


Materials Science and Engineering A-structural Materials Properties Microstructure and Processing | 1993

Modellization and numerical simulation for bulk crystal growth process

Thierry Duffar; C. Barat; J.-Ph. Nabot

Abstract The aim of this work was to study the relevance of numerical simulation to improve the process control for French industrial crystal growers. This investigation focused on the growth of semiconductor and halogenide crystals by the Bridgman technique. Calculations were performed by the finite element method and, for comparison, experiments were carried out in Bridgman pulling machines working either in the laboratory or in industrial plants. Comparison of calculations with experimental data has revealed a good agreement and a satisfactory reliability. Finally, it resulted in a better understanding and various improvements of industrial processes.


Journal of Crystal Growth | 1995

Some problems of stability analysis of movable meniscus

V.A. Tatarchenko; J.Ph. Nabot; Thierry Duffar; E.V. Tatarchenko; B. Roux


Archive | 1997

Device for the tight crossing of a partition by a mobile member

Jean Delepine; Thierry Duffar; Jean-Philippe Nabot; Bernard Wales


Archive | 1992

Convection related radial segregation in an idealized horizontal Bridgman configuration

Jean-Paul Garandet; Thierry Duffar; Jean-Jacques Favier


Archive | 1997

Sealed feedthrough for a moving part

Jean Delepine; Thierry Duffar; Jean-Philippe Nabot; Bernard Wales

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