Microstructural evolution and piezoelectric properties of thick Pb(Zr,Ti)O₃ films deposited by multi-sputtering method: Part I. Microstructural evolution

Thick and crack-free Pb(Zr,Ti)O₃ [PZT] films were fabricated on platinized silicon substrates by a multisputtering technique. The PZT films were deposited on the Si substrate by the radio frequency magnetron sputtering method using a single oxide target. As the film became thicker, its grain size increased. Therefore, the microstructure of the film was able to be controlled by repeatedly depositing thin layers. In addition, by using a seed layer with the same composition but a much smaller grain size, it was possible to further reduce the grain size of the film. When the film had a small in-plane grain size and a fibrous columnar structure, it was highly resistant to cracking, presumably because of its enhanced strength and structural stability. By exploiting these phenomena, highly dense, crack-free, and thick PZT films were successfully deposited up to a thickness of about 5 μm. The evolution of the crystallographic orientation of the film as a function of its thickness was also observed and correlated with the total strain energy of the system.