Effect of Thermal Stress on Orientation Control of CSD-Derived Pb(Zr0.53Ti0.47)O3 Thin Films

Abstract

Electrical properties of Pb(Zr0.53Ti0.47)O3 (PZT) thin films are significantly affected by the film orientation. Especially c-axis-oriented PZT thin films exhibit higher electrical properties. However, perfect orientation control to c-axis is very difficult, especially for the case of chemical solution deposition (CSD). Therefore, we tried to make clear the factors that affect the film orientation of the CSD-derived PZT thin films, by applying the thermal stress. We used stainless steel (SS) substrates with higher thermal expansion coefficients and the CSD-derived LNO seeding layer, which showed good lattice matching with c-plane of PZT and similar thermal expansion coefficient to the SS substrates, to apply the thermal compressive stress to the PZT thin film during cooling. As a result, we successfully deposited the selectively c-axis-oriented PZT thin film with higher remanent polarization, Pr, over 30 μC/cm2 and good squareness of the hysteresis loop. These results elucidate that the thermal compressive stress by the constraint force from substrate is very effective not only for the orientation contol of the resulting PZT thin films but also to improve the electrical properties of the PZT thin films. This strategy is essential to obtain the ferroelectric thin films with excellent electrical properties.