Growth instability due to lattice-induced topological currents in limited mobility epitaxial growth models

摘要

The energetically driven Ehrlich-Schwoebel (ES) barrier had been generallyaccepted as the primary cause of the growth instability in the form ofquasi-regular mound-like structures observed on the surface of thin film grownvia molecular beam epitaxy (MBE) technique. Recently the second mechanism ofmound formation was proposed in terms of a topologically induced flux ofparticles originating from the line tension of the step edges which form thecontour lines around a mound. Through large-scale simulations of MBE growth ona variety of crystalline lattice planes using limited mobility, solid-on-solidmodels introduced by Wolf-Villain and Das Sarma-Tamborenea in 2+1 dimensions,we propose yet another type of topological uphill particle current which isunique to some lattice, and has hitherto been overlooked in the literature.Without ES barrier, our simulations produce spectacular mounds very similar, insome cases, to what have been observed in many recent MBE experiments. On alattice where these currents cease to exist, the surface appears to bescale-invariant, statistically rough as predicted by the conventional continuumgrowth equation.