Sputter deposition and characterization of “epi-poly” Pb(Zr, Ti)O3 thin film on (100) Si substrate for MEMS applications

Monocrystalline Pb(Zr, Ti)O3 (mono-PZT) thin films are suitable for specific microelectromechanical systems applications. However, these films are more brittle than general polycrystalline PZT thin films. Herein, we focus on an epitaxial PZT thin film with multiple variants in the in-plane direction. Such a unique crystalline structure is expected to have properties intermediate between the mono- and polycrystalline PZT thin films. Such a film is called as "epi-poly" thin film in this paper. We formed an LaNiO3 buffer layer with three variants as an underlayer. PZT was then sputter-deposited onto it. Thus, a (100)-oriented epi-poly PZT thin film with three variants was obtained. Its piezoelectricity, ∣e31,f∣, dielectric constant, εr33, dielectric loss, and tanδ were measured to be approximately 9 C m−2, 750–800, and 0.02, respectively. Nano-indentation tests on the epi-poly and mono-PZT thin films indicated that the former had superior mechanical robustness than that of the latter.