  We describe a novel approach for the rational design and synthesis of
self-assembled periodic nanostructures using martensitic phase transformations.
We demonstrate this approach in a thin film of perovskite SrSnO3 with
reconfigurable periodic nanostructures consisting of regularly spaced regions
of sharply contrasted dielectric properties. The films can be designed to have
different periodicities and relative phase fractions via chemical doping or
strain engineering. The dielectric contrast within a single film can be tuned
using temperature and laser wavelength, effectively creating a variable
photonic crystal. Our results show the realistic possibility of designing
large-area self-assembled periodic structures using martensitic phase
transformations with the potential of implementing "built-to-order"
nanostructures for tailored optoelectronic functionalities.
