Directed assembly of photonic crystals through simple substrate patterning

We present molecular dynamics simulations of the epitaxial growth of high quality crystalline films for photonics applications from triblock Janus colloids. With a featureless substrate, the film morphologies were qualitatively similar to previously reported experimental results, with two stacking polymorphs appearing in nearly equal proportion. However, with a patterned substrate deliberately designed to be easy to fabricate by standard photolithography techniques, both the grain size and selectivity towards the photonically active polymorph were greatly improved. We also evaluated the effect of particle flux to find that lower flux led to higher quality crystals, while higher flux led to frustrated films with smaller crystalline domains. Our results suggest that carefully engineered but simple to manufacture patterned substrates could yield self-assembled single crystals of sufficient quality to exhibit a complete photonic bandgap.