Direct Piezoelectric Force Microscopy: Applications Towards the Characterisation of Multiferroic stacks

The characterisation of BaTiO 3 thin films by direct piezoelectric effect microscopy (DPFM) is presented. The technique allows for both the mapping of the polarisation of the surface, by imaging lines of constant electrostatic force over a polarised region, but also for the characterisation of the direct piezo coefficient, via the acoustically excited, lock-in demodulated, induced piezo-voltage response of the same region. The ability to objectively discriminate between piezo-effect and surface polarisation is crucial for the characterisation of artificial multiferroic stacks, where the polarisation response of buried layers can be masked by conductive caps, but the piezo response persists.