Monolayers of monodisperse latex spheres of micron size were used as deposition masks to fabricate arrays of ferroelectric nanostructures by pulsed laser deposition using a BaTiO3 target. First, arrays of well-ordered structures were prepared on SrTiO3:Nb (100) single-crystal substrates at room temperature. Investigations of these isolated as-deposited nanostructures by atomic force microscopy revealed that they have a pyramid-like shape with about 200 nm lateral size at half their height and form a regular hexagonal pattern. Then postdeposition annealing was used to crystallize the nanostructures. The ferroelectric properties of the crystalline structures were investigated by scanning force microscopy in piezoresponse mode. Piezoelectric hysteresis loops were recorded, demonstrating that the barium titanate nanopyramids have a remanent polarization and are switchable by an electric field, i.e., they are indeed ferroelectric.

Ma, W., Harnagea, C., Hesse, D., & Gösele, U. (2003). Well-ordered arrays of pyramid-shaped ferroelectric BaTiO3 nanostructures. Applied Physics Letters, 83(18), 3770–3772.