Abstract Research on Marangoni flow of molten silicon in a half-zone structure, which corresponds to floating-zone configuration, was carried out in microgravity and earth gravity conditions. Flow and temperature fields were successfully observed using X-ray radiography and temperature measurement using fine thermocouples. Temperature oscillation measurement showed that the critical Marangoni number for transition from an oscillatory flow with a single frequency to one with multiple frequencies is about 3000. Observation of the flow's structural instability showed that the mode was either m = 1 or m = 2 depending on the aspect ratio of the liquid column. Measurement of surface tension and its temperature coefficient for molten silicon suggested that Marangoni flow is sensitive to oxygen partial pressure of ambient atmosphere. Investigating Marangoni flow on a flat surface, which corresponds to Czochralski configuration, would supply a new viewpoint on the Czochralski growth of silicon single crystals.