In order to understand the influence of crucible geometry combined with natural convection and Marangoni convection on melt flow pattern, temperature and pressure fields in silicon Czochralski crystal growth process, a set of numerical simulations was conducted. We carry out calculation enable us to determine temperature, pressure and velocity fields in function of Grashof and Marangoni numbers. The essential results show that the hemispherical geometry of crucible seems to be adapted for the growth of a good quality crystal and the pressure field is strongly affected by natural and Marangoni convection and it is more sensitive than temperature.

The effects of several growth parameters in cylindrical and spherical Czochralski crystal process are studied numerically and particularly, we focus on the influence of the pressure field. We present a set of threedimensional computational simulations using the finite volume package Fluent in two different geometries, a new geometry as cylindro-spherical and the traditional configuration as cylindro-cylindrical. We found that the evolution of pressure which is has not been studied before; this important function is strongly related to the vorticity in the bulk flow, the free surface and the growth interface. It seems that the pressure is more sensitive to the breaking of symmetry than the other properties that characterize the crystal growth as temperature or velocity fields.

Abstract. In order to understand the influence of a semispherical crucible geometry combined with different convection modes as a thermocapillary convection, natural convection and forced convection, induced by crystal rotation, on melt flow pattern in silicon Czochralski crystal growth process, a set of numerical simulations are conducted using Fluent Software. We solve the system of equations of heat and momentum transfer in classical geometry as cylindrical and modified crystal growth process geometry as cylindro-spherical. In addition, we adopt hypothesis adapted to boundary conditions near the interface and calculations are executed to determine temperature, pressure and velocity fields versus Grashof and Reynolds numbers. The analysis of the obtained results led to conclude that there is advantage to modify geometry in comparison with the traditional one. The absence of the stagnation regions of fluid in the hemispherical crucible corner and the possibility to control the melt flow using the crystal rotation enhances the quality of the process comparatively to the cylindrical one. The pressure field is strongly related to the swirl velocity.

Since their introduction at the beginning of the 19th century, Casuarina species have become important components of the Algerian landscape, yet the numbers of species present in Algeria and their identity, distribution, and symbiotic status are still not well understood. A survey conducted on 2,304 trees in 96 Casuarina stands across Algeria indicates that they are represented exclusively by five species: Casuarina cristata Miq., C. cunninghamiana Miq., C. equisetifolia L., C. glauca Sieber ex Spreng. and C. junghuhniana Miq. Two species, C. cunninghamiana and C. glauca, were the most common – the former occurring more often in the relatively humid and temperate areas of the country while the latter is most frequent in the drier and warmer areas. Production of seedlings of C. cunninghamiana and C. glauca in 12 nurseries resulted in low rates of spontaneous mycorrhizal infection frequency and nodulation, suggesting that inoculation of seedlings with selected mycorrhizal fungi and/or Frankia strains in the nursery would be necessary to improve their establishment in the field. This study is the first survey of the geographical distribution of Casuarina species in Algeria and should lead to more efficient utilization of this widely used tree genus in Algeria.

No abstract