IN SITU MEASUREMENTS OF STRESS WITH TEMPERATURE IN THIN FILM Pb_xBa_{1 − x}TiO₃

ABSTRACT

In situ curvature measurements were used to monitor the macroscopic film stress with temperature in well-oriented thin films of Pb_xBa_{1 − x}TiO₃ (x = 0.2, 0.5, 1.0) on single crystal MgO (001). Successive measurements were made between room and the growth temperature, 650 °C. The films were found to be in compression at room temperature. The compressive stresses in the films continually decreased at nearly constant rates with increasing temperature, and near the Curie temperature for each composition T _c(x) these rates increased. Energy minimization calculations were used to predict the changes in the domain volume fractions and the film stresses with temperature. We find qualitative agreement between the predicted and measured behavior of the domain volume fractions. However, the stress in the films is not relaxed below T _c(x) as expected. We discuss the effects that may inhibit this relaxation, namely film thickness, growth effects, and the presence of grain boundaries.

Keywords:

• Ferroelectrics
• polydomain structures
• thin films
• film stress
• stress relaxation
• CGS
• Coherent Gradient Sensing

ACKNOWLEDGMENTS

This work has been supported by ARO MURI grant number DAAD19-01-1-0517.