Growth stages of sol-gel derived PZT(30/70) on Pt/Ti/SiO₂ as shown by SPM (PFM and topography)

The integration of PZT into devices based on silicon is of great interest for the further miniaturisation of sensors and actuators and their integration into MEMS devices. PZT is the material of choice for these applications due to it's good piezoelectric properties. When PZT is produced by sol-gel the material undergoes a series of transformations. After the initial drying stage the sol transforms into the non-ferroelectric pyrochlore phase. Upon further heat treatment the ferroelectric perovskite phase is formed. A single layer (ca. 70nm thick) film of PZT has been deposited onto highly [111] orientated Pt. The degree of transformation from the pyrochlore phase to the perovskite phase has been recorded using XRD and a variety of scanning probe techniques, including Piezoresponse force microscopic (PFM) and contact mode topographic analysis. A map of the surface topography and the PFM image show variations in both topography and distribution of piezoelectric regions as the perovskite/ pyrochlore ratio changes. The method by which the changes occur can be explained by the nucleation of perovskite phase from the pyrochlore phase. The range of temperatures examined were 400 to 530°, the sample being left at each temperature for 5 minutes. It was found that fully transformed perovskite PZT was produced at 530°C. The XRD pattern for the sample shows that it is [111] orientated.