Enhanced growth instability of strained film on wavy substrate

We demonstrate that the growth of a strained film is inherently less stable on a wavy substrate than on a flat substrate. For small surface undulation, the lowest strain energy state is for the film surface to adopt the same wavelength as the substrate surface in an antiphase configuration at the early stage of growth. The critical wavelength (lambda(c)) of growth instability on a wavy substrate is half of that on a flat substrate (lambda(0)). It increases linearly with increasing film thickness (t) as lambda(c)=lambda(0)/2+pi t. Implications for strain directed self-assembly on patterned substrate are discussed. (C) 2008 American Institute of Physics.