Unsteady Growth ofBaB2O4Single Crystal from High-Temperature Solution

Two-dimensional growth of BaB2O4 single crystal from high-temperature solution was performed, and the motion of solid-liquid interface was observed in real time by differential interference microscopy. Results show that the solid-liquid interface exhibits the morphology of a vicinal face where steps with height of several microns are observed. The measurements of growth rate V and step propagating velocity υ show that both V and υ fluctuate by up to 40∼50% of their average values, respectively, under constant external conditions. Such intrinsic fluctuations with time interval of the order of one second is mainly the result of step bunching, which has been confirmed by the gradual decrease of step spacing when approaching the edge of the growing interface. Besides above fluctuations, a longer-period oscillation of V (period interval of 4∼5 seconds) is obtained for relatively rapid growth, which is triggered by the periodical alteration of step propagating directions.