INFLUENCE OF ATMOSPHERE ON MOLTEN SILICON DENSITY

The influence of atmosphere on the density of molten silicon has been studied. The density was measured by an improved Archimedean method wi th the accuracy of 1.1%. The density under argon gas mixed with hydrog en 7.15% is found to be equivalent to that under pure argon gas at the melting; point, but showed higher values at higher temperatures (1430 -1500 degrees C) with the thermal volume expansion coefficient of abou t 8.8 x 10(-5) K-1. The density under the hydrogen-containing argon al so shows a time-dependent variation over 5 h after melting. The solubi lity of hydrogen in molten silicon is estimated to be below 3 x 10(18) atoms cm(-3). This result suggests that the increase of the density i n the presence of hydrogen is caused by the change of the arrangement of the silicon atoms.