PERIODIC ROUGHENING TRANSITIONS IN DIFFUSION-LIMITED GROWTH

By interference contrast microscopy and atomic-force microscopy, we ob served for the first time a periodic roughening transition occurring o n the surface of crystal aggregates of NH4Cl grown in agarose gel. The experiments show that the period of the roughening transitions depend s on both NH4Cl concentration and agarose gel density. We suggest that this phenomenon arises from the competition of the interfacial growth and the nutrient transfer, a common but usually ignored effect in man y growth systems.