Observation of surface oscillation in a molten silicon column using Moire interferometry

Surface oscillation due to oscillatory Marangoni flow in a Liquid bridge of molten silicon was observed using phase-shift interferometry. The molten silicon surface was described by phase-distribution profiles with a sampling rate of 30 Hz. From the phase-distribution profiles, we analyzed the oscillation of the radial displacement, axial gradient, and azimuthal gradient of the molten silicon surface. The oscillation of the radial displacement and the axial gradient showed an in phase relationship. However, in-phase oscillation was not observed between the radial displacement and the azimuthal gradient. Marangoni frequencies was observed at 0.1 to 5 Hz in which the frequencies higher than 1Hz had not previously been observed by conventional methods. We also found eigenfrequencies of the liquid bridge at 8.8Hz and 11.5Hz.