X-ray diffraction of ferroelectric nanodomains in PbTiO3 thin films

X-ray diffraction constitutes a powerful technique with which to characterise ferroelectric domains. Here we describe the principles of ferroelectric nanodomain diffraction and present some results for PbTiO3 thin films grown under tensile strain on two different substrates, with thicknesses below and above the critical thickness for strain relaxation. The combination of conventional and grazing incidence diffraction and the analysis of the scattering between Bragg peaks allowed the identification of a new polar symmetry in ultra-thin films with only anti-parallel 180 degrees domains. Thick films showed tetragonal 90 degrees ferroelectric/ferroelastic domains instead, with a depressed TC and a domain periodicity largely independent of temperature