融液ミステリーの追跡 : 新技術事業団創造科学事業「融液動態プロジェクト」結果報告

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In our study of molten Si, the energy dispersive X-ray diffraction technique revealed the reduced intensities structure factor and temperature dependent change of the nearest interatomic distance and the coordination number as compared with the previous findings. A small angle scattering technique showed that there is no evidence of cluster formation in Si melt near melting temperature against an expectation. The extended X-ray absorption fine structure spectroscopy revealed that impurity level gallium atoms are tightly bound by three Si atoms in Si melt.A measurement of Si melt density after melting gave a clear tendency of relaxation with an equilibration period of 3 hours. The influence of the relaxation time to grown crystals was studied and found evident in formation of point defects. The density measurement after relaxation revealed that the anomalous change takes place in the temperature range up to 15 degress higher than the melting point. In this region, thermal expansion was calculated about an order of magnitude lager than that in the higher temperature region. The property anomaly in the same temperature range was also found for surface tension and viscosity. Addition of 0.1% boron did not show any effect while that of 0.1% gallium or antimony wiped out the anomaly. We found that in highly antimony doped Si melt a volatile species of Sb_2O forms in proportion to the square of Sb concentration and evaporates. Also determined are the evaporation rates of SiO and Sb_2O. Electrical resisticity, thermal diffusivity and spectral emissivity were also studied and it was deduced that four electrons from each Si atom were delocalized liberated into the bulk of the melt. Conventional computer simulation techniques were closely checked and the result was compared with that by the X-ray fluoroscopic observation of Si melt in a crucible. They agreed with each other qualitatively. The calculation using the newly determined evaporation rate revealed that the experimentally found radial oxygen distribution in the crystal agreed well with the calculation result. The simulation algorism was improved by analyzing a three dimensional mesh system and introducing a computation technique called k-ε model. The result of the calculation based on our new algorism was found remarkably consistent with the experimentally determined temperatures at some localities of Si melt in the crucible.
日本結晶成長学会の論文
1996-09-25

融液ミステリーの追跡 : 新技術事業団創造科学事業「融液動態プロジェクト」結果報告

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