Sensitivity of Piezoelectric Ultrasonic Microsensors with Sol-Gel Derived PZT Films Prepared through Various Pyrolysis Temperatures^†

Sensitivity of piezoelectric-diaphragm type ultrasonic microsensors were investigated with sol-gel derived lead-zirconate-titanate (PZT) films prepared through various pyrolysis temperatures. The residual stress of the PZT film should be precisely controlled because the sensor diaphragms show static deflection by buckling and highly sensitive sensors have been realized on upward-buckled diaphragms whose buckling direction and deflection are determined by the stress. The films were prepared under pyrolysis temperatures in the range from 250 °C to 400 °C and for (100)- or (111)-orientation. Higher pyrolysis temperature resulted in lower film stress and larger buckling deflection of the diaphragms. The (111)-oriented films showed the higher sensitivity in the higher pyrolysis temperatures. The (100)-oriented films, however, showed the highest sensitivity in the lowest pyrolysis temperature (250 °C).