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 p iezoelectric properties of lead zirconate titanate (PZT) films in the morphotropic phase boundary composition. An AFM tip was used, in the c ontact mode, as a top electrode to apply a voltage to polarize the fil m and to apply an oscillating field to obtain piezoelectric coefficien ts and piezoelectric loops from the inverse piezoelectric effect induc ed on the film. The piezoelectric coefficient in nanoregions was measu red as a function of stress by changing the applied force with the AFM tip. The piezoelectric coefficient was found to decrease monotonicall y as the stress was increased. It was additionally found that as the s tress was decreased to its initial value, the effective piezoelectric coefficient approximately followed the same trace on increasing the st ress. These results suggested that non-180 degrees domains did not con tribute to the measured piezoelectric coefficient for the stress level s applied and that the mobility of ferroelastic domain walls is very l ow for these PZT films.