Emergence of supersteps on KH2PO4 crystal surfaces.

In situ AFM investigation of growth on the [100] face of KH2PO4 in the presence of Al(III) and other trivalent metals reveals the emergence of a new type of morphological feature-the superstep. Supersteps, or step bunches consisting of 50-1500 elementary steps, are responsible for growth at all supersaturations and exhibit behavior not predicted by accepted models. The step velocity of the superstep is greater than that of single atomic steps and increases with step height. The steepness of the step riser reaches a limiting value of only 11.8 degrees.