Morphological instability of Cu vicinal surfaces during step-flow growth

The step-flow growth of Cu on vicinal Cu surfaces, Cu (1 1 17) and Cu (0 2 24), is investigated by variable-temperature scanning-tunneling microscopy. These vicinal surfaces have identical terrace widths but their step orientation differs by 45 degrees. Upon growth, the surfaces develop a step-meandering instability, resulting in an in-plane patterning of the surfaces with a temperature- and flux-dependent characteristic wavelength lambda (u). The instability-induced structural patterns depend on the step orientation and are the manifestation of the Bales-Zangwill instability in both cases. The selected characteristic wavelength is interpreted as the interplay of a destabilizing effect due to the presence of the Ehrlich-Schwobel barrier and a stabilizing mechanism presumably due to "diffusion noise." As a result, lambda (u) is proportional to the one-dimensional nucleation length l(n) along a straight step, involving the diffusion barrier along both the (110) and (100) step orientations on Cu(001).