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°. 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-Schwöbel 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).