RELAXATION OF THE STEP PROFILE FOR DIFFERENT MICROSCOPIC MECHANISMS

Theoretical and experimental studies of the rate of decay of metastabl e structures are compared quantitatively. The effect of decay mechanis m, size, and periodicity of the structure on the rate of decay is eval uated within both a coarse-grained step-based model and a continuum mo del. For high-amplitude structures, the decay scales with size (N) and time as (t/N-alpha)(-beta). The exponents alpha and beta depend on th e mass transport mechanism. The size scaling is alpha=4 for locally co nserved diffusive flux and alpha=2 for locally nonconserved flux. The time scaling exponent is beta=1/5 for diffusive limited mass transport and beta=1/4 for step attachment limited mass transport. Experiments were performed on metastable structures of controlled sizes 3-5 nm in height, prepared by direct current heating on Si(111). Quantitative ag reement with theoretical predictions of both scaling (alpha=4.3+/-0.5, beta=0.2+/-0.3) and absolute rate of decay were obtained. (C) 1996 Am erican Vacuum Society.