Piezoelectric hysteresis measurement using atomic force microscopy

Local piezoelectric hysteresis of Pb(Zr,Ti)O3 thin films were measured using atomic force microscopy and lock-in amplifier. PZT films were prepared by sol-gel processing and rf-sputtering. PZT films exhibit inverse piezoelectric response on application of a voltage. To detect such a small response of the thin (less than 100 nm in thickness) PZT films, ac modulation technique was used. Actual displacements were obtained by the calibration of the first harmonic signal (Acos) from X-cut quartz crystal (piezoelectric coefficient of 23pm/V). Coercive voltages and the maximum displacements were measured, respectively, from the deconvoluted phase and amplitude. As calibrated, the effective local piezoelectric coefficient were 5.8 and 11.5 in arbitrary unit from sol-gel processed and sputtered films. In case of the PZT films processed by sol-gel technique showed a larger local variation of the piezoelectric response and smaller displacements than the sputtered PZT films with similar film thickness.