Strain behavior of thin film PbZr0.3Ti0.7O3 (30/70) examined through piezoforce microscopy

Using an atomic force microscope (AFM) modified to perform piezo-AFM we have investigated the piezoelectric response of sol-gel thin film lead zirconate titanate (PZT 30/70, PbZr0.3Ti0.7O3) on Pt-Ti/SiO2/Si to a quasi-dc electric field. By applying a sinusoidal 2 Hz ac waveform between the AFM cantilever and ground we have generated strain field, or butterfly loops for the PZT film. Coercive fields for the thin films have been calculated from the minimum point of the strain before reversal for the system and are shown to be -30 and +32 V/mum in absolute terms and -23 and +39 V/mum in terms relative to the charge trapped at the electrode interface. The maximum strain of the system was shown at applied biases of +/-10 V and was 0.3% at a bias of +10 V, although at this bias the sample was not showing saturated behavior. By relating the offset of the butterfly loops to the charge density generated by defects at the PZT-electrode interface, calculated to be 0.025 Cm-2, an estimate of the number of defects at the interface has been calculated to be one defect for every 6 nm2 of surface, or one defect in every 40 unit cells. (C) 2003 American Institute of Physics.