In Situ Annealing Studies of Sol‐Gel Ferroelectric Thin Films by Spectroscopic Ellipsometry

Spectroscopic ellipsometry was utilized to follow in situ the annealing of sol‐gel Pb(Zr,Ti)O₃ films on sapphire and platinum‐coated silicon substrates. Low‐temperature processes, such as pyrolysis of organics and film densification, could be identified readily. Crystallization of the perovskite phase was initiated between 500° and 600^deg;C for the film on sapphire. This was coincident with the roughening of the film surface. Identification of higher‐temperature processes in the film on platinum‐coated silicon was complicated by temperature‐dependent changes in the substrate. In situ annealing studies on the substrate alone confirmed that, for the lengthy annealing profiles utilized in these experiments, substantial and irreversible changes in the effective substrate dielectric function occurred at temperatures >550^deg;C. In addition, the role of extended, high‐temperature annealing on the optical frequency dielectric properties of the films was investigated.