Stress-Driven Alloy Decomposition during Step-Flow Growth

A surface under stress is morphologically unstable. In normal step-flow growth, this is manifested as a step-bunching instability. Here it is shown that for alloy growth the resulting inhomogeneous strain drives decomposition of the alloy. At the same time, this decomposition “screens” the inhomogeneous strain, partially suppressing the instability. In contrast to a previous continuum model, stress-driven alloy decomposition during step flow is never destabilizing, nor does it ever fully stabilize the surface. A possible mechanism for spontaneous superlattice formation is suggested.