Morphological evolution and ordered quantum structure formation in heteroepitaxial core--shell nanowires.

We have performed three-dimensional dynamic simulations to study strain-driven morphological evolution and the formation of quantum structures on heteroepitaxial core--shell nanowire surfaces. Our simulations show that depending on geometric and material parameters, such as the radius of the wire, the thickness of the shell, and the mismatch strain, various surface morphologies including smooth core--shell nanowire surfaces, nanoring arrays, nanowire arrays, and ordered quantum dot arrays can be obtained by controlling initial surface configurations through prepatterning. It is also shown that these quantum structures may be trapped in a metastable state and may undergo a series of metastable state transitions during subsequent dynamic evolution. Our results identify possible pathways for fabrication of ordered quantum structures on the epitaxial core--shell nanowire surfaces and provide guidelines for achieving smooth core--shell structures.