Abstract
Growth rate of a dislocation-free Ba (NO 3) 2 crystal was measured in microgravity by real-time phase-shift interferometry (RPSI) which could resolve the steps with one nm high in 1/30 s. Due to the temperature decrease by 6 degree to grow the crystal, the thermal distortion of the glass window, on which the seed crystal was glued, was found to be 20 times larger than the growth of the seed crystal. This difficulty was overcome by measuring the distortion rate of the glass window by analyzing the phase-shift interference fringes precisely to be subtracted from the apparent growth rate of the crystal face. This successful analysis lead a clear difference of growth mechanism at low supersaturation: homogeneous 2D-nucleation in microgravity whereas heterogeneous 2D-nucleation in normal gravity. This difference would also lead to the difference in the perfection of crystals in microgravity.
