The role of nanoporosity on the local piezo and ferroelectric properties of lead titanate thin films

Nanoporous and dense ferroelectric PbTiO3 thin films are prepared by a modified sol-gel process. The presence of nanoporosity, with similar to 50 nm pore size formed using a block polymer as a structure-directing agent, markedly affects the microstructure, crystallization and ferroelectric properties of the film. The crystallization of the tetragonal phase is enhanced in nanoporous films. It is suggested that the decomposition of the block-copolymer in porous films triggers the crystallization of the perovskite phase at low temperatures via the local increase of temperature. Consequently, nanoporous films with improved tetragonality exhibit enhanced piezoelectric coefficients, switchable polarization and low local coercivity. By providing a means of achieving enhanced properties, nanoporosity may have a broad impact on the applications of ferroelectric thin films.