Strong interactions at the interface between a crystalline film and substrate can impart new structure to thin films. Here, a germanium surface (purple atoms) squeezes a BaTiO3 thin film above, revealing a hidden phase not seen in the bulk. The hidden phase of BaTiO3 shows oxygen octahedra cages (shaded in aqua) alternating in size. By combining theory, synchrotron x-ray diffraction, and electron microscopy, a new materials design approach has uncovered hidden traits of a material that can be expressed through articulated forces at an interface.
