Abstract
The surface tension of molten silicon was successfully measured by an oscillating drop method using electromagnetic levitation over a wide temperature range from 1100 to 1500°C including the undercooling condition of 300K. Correction proposed by Cummings and Blackburn (J. Fluid Mech. 224 (1991) 395) was utilized for a deformed droplet under normal gravity condition. Silicon crystals heavily doped with B and Sb (resistivity as low as 1×10-4Ω⋅m) were successfully melted and levitated. The surface tension of molten silicon was 783.5×10-3N⋅m-1 at the melting point of 1410°C within the measurement accuracy of 3-4%. Its temperature coefficient was -0.65×10-3N⋅m-1⋅K-1. Secondary ion mass spectroscopy analysis showed that O and Sb evaporated during melting, while the B concentration after melting was unchanged. This means that surface tension and its measured temperature dependence correspond to those for a contamination-free silicon melt. Levitation and oscillation were confirmed using a parabolic flight of the NASA KC-135 aircraft. Surface tension measurement will be sure to be measured without correction using 10-second microgravity at a drop shaft.
