Effects of residual stress on the electrical properties in PbZr_0.52Ti_0.48O₃ thin films

In this paper, Pb(Zr_0.52Ti_0.48)O₃ (PZT) thin films were prepared on Pt/Ti/SiO₂/Si substrates via sol–gel method. The effects of residual stress on the electrical properties in PZT thin films were investigated. There is no significant difference in grain size and orientation for PZT thin films, indicating that the influences of grain size and orientation on electrical properties of PZT thin films can be neglected. The residual stresses in PZT thin films, which decrease with increase in the film thickness, were detected by the phonon mode shift of Raman scattering. In the thin films, the interface between PZT thin films and platinum electrodes is the main factor that affected dielectric properties. As the film thickness increases, the contribution of the interface is increasingly attenuated and the residual stress is the main factor. To relieve some of the residual stress, there are more 90° domains to form, which can improve the ferroelectric and piezoelectric properties of PZT thin films.

The value of dielectric constants decreases at 1 MHz, and tan δ increases with the decrease in film thickness. In this paper, the processing was designed to control grain size and crystal orientation. Therefore, residual stress and interface are the main factors that affect the dielectric constant. For the sample with the thickness of 162 and 324 nm, there is a ~45 % increase in measured dielectric constant and this change appears to be too much to be accounted for by the residual stress alone. The main factor that affects dielectric constant in the thinner films is the interface which can dilute the effective dielectric constant. As the film thickness increases, the contribution of the interface is increasingly attenuated and there is only 4 % change in the dielectric constant, indicating that residual stress is the main factor that affected dielectric constant.