Stress-dependent piezoelectric properties of ferroelectric lead zirconate titanate films studied by atomic force microscopy

Atomic force microscopy (AFM) has been used for the determination of piezoelectric properties of lead zirconate titanate (PZT) films in the morphotropic phase boundary composition. An AFM tip was used, in the contact mode, as a top electrode to apply a voltage to polarize the film and to apply an oscillating field to obtain piezoelectric coefficients and piezoelectric loops from the inverse piezoelectric effect induced on the film. The piezoelectric coefficient in nanoregions was measured as a function of stress by changing the applied force with the AFM tip. The piezoelectric coefficient was found to decrease monotonically as the stress was increased. It was additionally found that as the stress was decreased to its initial value, the effective piezoelectric coefficient approximately followed the same trace on increasing the stress. These results suggested that non-180° domains did not contribute to the measured piezoelectric coefficient for the stress levels applied and that the mobility of ferroelastic domain walls is very low for these PZT films.