Evaluation of longitudinal displacement for lead zirconate titanate films

An atomic force microscope (AFM) probing system was connected with a ferroelectric test system to measure the polarization hysteresis (P-E) curve and longitudinal displacement properties simultaneously with a large AC drive signal at 5 Hz, since this measurement system has the advantages of enabling dynamic evaluation of longitudinal displacement and direct comparison of the ferroelectric and piezoelectric properties. With decreasing the top electrode diameter from 500 to 30 mum, the longitudinal displacement direction changes from negative to positive since the longitudinal piezoelectric effect becomes dominant. The longitudinal piezoelectric constant calculated with a unipolar signal (+5 V, 5 Hz) was d(33) = 108 pm/V for a 30-mum-dia top electrode. This value is lower than that of bulk PZT but higher than that of reported data measured using the double-beam laser interferometer or the AFM with a small AC signal of about 1 kHz.