Surface tension of molten silicon measured by microgravity oscillating drop method and improved sessile drop method

The surface tension of molten silicon was measured using both the oscillating drop method and an improved sessile drop method. The oscillating drop method was used under microgravity conditions. The purity of the silicon sample was 9N. The atmosphere was Ar-3% H2 gas purified using platinum asbestos and magnesium perchlorate. The result measured using the oscillating drop method agrees very well with that measured using the sessile drop method, and is expressed by the following equation: γ = 733 − 0.062(T − 1687), where γ is the surface tension (mN/m) and T is the temperature (K). The standard deviation of the scatter of the values obtained by the oscillating drop method is less than 1% which is smaller than that obtained by the sessile drop method. In addition, the surface tension can be measured over a wider temperature range including the undercooled state using the oscillating drop method. Accordingly, a much more accurate temperature dependence is obtained.