Crystallisation surface microtopography of [1120]- Direction growth sapphire crystal

Observations of the microtopography evolution on a crystallisation surface of sapphire crystal grown from Al2O3 melt show the smooth region was formed by thin atomic layers with wave-like edge trace and the rough region was mainly of aligning long bar-like structure formed by many spiral hillocks spreaded along lines corresponding to the direction [8803]. Moreover, decreasing the undercooling would enhance the width of the bars and decrease the width of the grooves adjacent the bars. According to these observations, the growth mechanism of the smooth region is believed to be the 2D nucleation mechanism and that of the rough region is the spiral growth mechanism. Consequently, a conclusion was drew that the controlling growth mechanism of sapphire crystal grown from melt through SAPMAC method is 2D nucleation mechanism.