Melt Flow Structure Research Articles

Melt layer solidification of fatty acids in a rectangular cell

Experiments have been performed on the impurity incorporation in the solid layer grown from a binary melt of myristic acid and palmitic acid using a rectangular cell with well-controlled temperature. The binary melt forms a simple eutectic phase diagram. Direct numerical simulations of melt solidification were carried out in order to validate the new theory of interfacial solute distribution proposed by the present authors [J. Chem. Phys. 109, 7468 (1998)]. The theoretical predictions of purity or impurity concentration profile in the solid layer agreed well with the experimental measurements. The purity profile inside the solid layer was found to be basically controlled by the flow structure of melt that essentially contributed to the transport phenomena of heat and mass near the solid layer surface.

Turbulent transport of oxygen in the Czochralski growth of large silicon crystals

Rigorous control of oxygen concentration in a large diameter silicon crystal grown by the Czochralski process is a challenge for the crystal growers. In this work, the renormalization group (RNG) method is employed to simulate the turbulent flows in a large melt with high turbulence level. It is found that the oxygen solubility of silica crucible, the evaporation of oxygen from the free surface, and the melt flow structure greatly affect the oxygen transport. Details of the transport mechanisms of oxygen in a large melt are investigated for various process conditions.

Density anomaly effect upon silicon melt flow during Czochralski crystal growth I. Under the growth interface

Temperature fluctuations under the growth interface region were measured to evaluate the flow structure during the Czochralski silicon growth process. The impurities which influence the density anomaly of the silicon melt are doped as experimental parameters. The flow structure of this region was found to be basically a random one that is supposed to represent the “soft turbulence” induced by Rayleigh-Bénard convection. The addition of gallium to the melt changes the flow structure to a laminar-like one when the melt depth is shallow while the flow structure is still similar to a soft turbulence in the cases of boron-doped and undoped at the same melt depth. These results suggest that the density anomaly of the silicon melt influences the melt flow structure of this region.

Analysis of melting around a moving heat source

This paper presents an analysis for simulating melting heat transfer around a moving, horizontal, cylindrical heat source. Motivated by the experimental observations, the melt domain is divided into two regions, namely, the close-contact region and the melt pool region. Two mathematical models are formulated and solution procedures are developed accordingly. The temperature and the flow fields in the two regions are calculated for a constant surface temperature heat source and the resulting velocity of the source and motion and shape of the interface are determined. The effects of the prescribed surface temperature of the source and its density, as well as influence of natural convection in the melt pool, are investigated and reported. The predicted melt flow structure and the motion and shape of the solid-liquid interface are found to be in good agreement with the experimental observations when natural convection in the melt is included in the model.