Thermodynamics of 3D diamond-like epitaxial (film) morphologies on 1D modulated substrate: Weak crystallization...

Being inspired by recent theoretical findings in block copolymer ordering, we present, within the simplest version of the Landau weak crystallization theory, a consistent treatment of the thin film thermodynamics. It is first shown that a proper design of the period of a 1D modulated substrate results in the formation of a 3D morphology whose symmetry is close to a cubic diamond one and differs from the latter due to a symmetry violation caused by the block copolymer-substrate interaction. The corresponding phase portraits are built. With a decrease in the temperature, the diamondlike morphology becomes less stable until it turns (via the 1st order phase transition) into the lamellar phase. On the contrary, with an increase in the substrate selectivity, the lamellae become less stable and, finally, turn into the diamondlike morphology.