Transient Laser Heating Enabled Nanocomposite Structures from Block Copolymers toward Photonic & Phononic Quantum Materials

Organic amphiphilic block copolymers swelled by carbon precursors self-assemble into a cocontinuous network mesophase via solvent vapor annealing. After carbonization in an inert atmosphere, the resulting mesoporous resin/carbon thin films are backfilled with amorphous silicon, acting as templates. The thermal stability of the templates derived from polymers is significantly enhanced via nanosecond transient laser heating to allow the crystallization of Si (temperatures upward of 1400 °C). Melting and recrystallization of Si during this highly non-equilibrium ultrafast time frame enable conformal template backfilling and the polycrystalline silicon inherits the mesostructural order of the 3D resin/carbon templates. Detailed analysis of X-ray scattering data reveals symmetry reduction from cubic alternating gyroids to orthorhombic networks with D2 point group symmetry. Such unique nanostructures from block copolymers obtained under non-equilibrium laser heating conditions could pave the way to topological photonic and phononic metamaterials in this growing field of soft matter enabled quantum materials.