Phase segregation of thin film polymer blends on Au nanopatterned Si substrates

We present a method for producing nano- to submicron scale, chemically heterogeneous surface patterns using an Ar ion mill. To observe the effects of the pattern on dewetting, thin films of PS and PMMA blends were spun-cast and annealed on these surfaces. The results showed that in hole morphologies the as-cast samples phase segregated with q ₂ ∼ q ₁/2, where q ₂ and q ₁ are the wave vectors characterizing the air interface morphology and the Au/Si pattern, respectively. Annealing resulted in the formation of a heterogeneous surface adsorbed phase covered by a PS layer at the air interface. The wave vector of the adsorbed phase, q ₄, obeyed the relationship q ₄ ∼ q ₁/2 for holes and q ₄ ∼ 2q ₁ for islands. The PS layer was observed to completely wet the surface adsorbed layer when the PS and PMMA domains were bicontinuous. Partial wetting occurred when either the PS or PMMA phase in the adsorbed layer was discontinuous.