Atomic force microscopic study of step bunching and macrostep formation during the growth of L-arginine phosphate monohydrate single crystals

The experimental results of the formation of step bunches and macrosteps on the (100) face of L-arginine phosphate monohydrate crystals grown from aqueous solutions at different supersaturations studied by using atomic force microscopy are described and discussed. It was observed that (1) the step height does not remain constant with increasing time but fluctuates within a particular range of heights, which depends on the region of step bunches, (2) the maximum height and the slope of bunched steps increases with growth One as well as supersaturation used for growth, and that (3) the slope of steps of relatively small heights is usually low with a value of about 8 degrees and does not depend on the region of formation of step bunches, but the slope of steps of large heights is up to 21 degrees. Analysis of the experimental results showed that (1) at a particular value of supersaturation the ratio of the average step height to the average step spacing is a constant, suggesting that growth of the (100) face of L-arginine phosphate monohydrate crystals occurs by direct integration of growth entities to growth steps, and that (2) the formation of step bunches and macrosteps follows the dynamic theory of faceting, advanced by Vlachos et al.