Numerical analysis of Oxygen control during growth of Czochralski silicon single crystals
In the present work, a set of 2D global furnace simulations accounting for oxygen dissolution and transport have been used to predict Oi content along the produced Silicon crystal. It is shown that Oi content is sensitive to several growth parameters (melt level, crucible rotation, etc.). Results indicate Oxygen tends to increase at the end of the crystal due to a combination of weakening of turbulence and planar velocity in addition to decrease of the melt free surface. Crucible rotation is the most influencing parameter at low melt level. Argon gas pressure and flow have a limited impact at low melt level.
Effect of crucible rotation and crystal rotation on the oxygen distribution at the solid-liquid interface during the growth of Czochralski monocrystalline silicon under superconducting horizontal magnetic field
Abstract This paper presents incorporating superconducting horizontal magnetic field, a very effective way with low power consumption and high field strength. To improve crystal quality of large diameter Czochralski monocrystalline silicon (CZ-Si) when it grows and to accurately describe the influential process parameters of oxygen distribution on the solid-liquid interface, 3D simulation is running on together with 2D/3D hybrid model established for obtaining boundary conditions. Compared with conventional horizontal magnetic field, the superconducting horizontal magnetic field shows that the increasing magnetic induction intensity helps to adjust the shape of solid-liquid interface, to reduce the oxygen content at the interface and to improve the uniformity of radial oxygen distribution. Further, when crucible is large and melt is deep, the low crucible rotation speed or the low crystal rotation speed is favorable for reducing the oxygen content at the interface. Suitable magnetic induction, low crucible and low crystal rotation speed processes are more conducive to improving the uniformity of the radial oxygen distribution at the interface during the growth. Finally, simulation and experiment results show the effectiveness for the proposed method.
The peculiar thermo-structural behavior of the anionic lipid DMPG.
Aqueous dispersions of the anionic phospholipid dimyristoyl phosphatidylglycerol (DMPG), around 100 mM ionic strength, are known to exhibit a thermal behavior similar to that of the largely studied lipid dimyristoyl phosphatidylcholine (DMPC), which undergoes a gel to liquid crystalline phase transition at 23 degrees C, well characterized by differential scanning calorimetry (DSC), and other methods. However, at low ionic strength, DMPG has been shown to present a large gel-fluid transition region, ranging from 18 to 35 degrees C. This intermediate phase is optically transparent and characterized by a continuous change in membrane packing. Structural properties of the DMPG gel-fluid transition region will be discussed, based on results obtained by several techniques: electron spin resonance (ESR) of spin labels at the membrane surface and intercalated at different depths in the bilayer; light scattering; DSC; small angle X-ray scattering (SAXS); and fluorescence spectroscopy of probes in the bilayer.