Fabrication of Monocrystalline-Based Composite PZT Thin Film with Polycrystalline Crack Stopper Structure

This paper reports on a new type of Pb(Zr, Ti)O3 (PZT) thin film, where monocrystalline (Mono) PZT is sectioned by narrow mesh-like polycrystalline (Poly) PZT. This Mono-Poly composite PZT thin film basically has unique characteristics of the Mono PZT such as reasonably high piezoelectric constant and low dielectric constant. In addition, accidental crack propagation in the Mono PZT is stopped by the Poly PZT. The motivation of this study is to solve the easy-to-fracture nature of single crystals, which is the case with Mono PZT. We successfully sputter-deposited the Mono-Poly composite thin film on a Si substrate covered with a patterned underlayer. Indentation tests demonstrated that the Poly PZT patterns prevented the crack propagation across Mono PZT areas. That is expected to improve the mechanical robustness of the entire film.