Surface morphology and ferroelectric properties of compositional gradient PZT thin films prepared by chemical solution deposition process

A series of PbTiO3/PbZrxTil−xO3 (PT/PZT) and PbZrO3/PbZrxTil−xO3 (PZ/PZT) compositional gradient thin films are obtained by chemical solution decomposition (CSD) method. The influences of buffer layers on surface morphology are investigated. Thin films with buffer layer are able to maintain the perovskite structure with (1 1 1)-preferred orientation. The surface microstructure and ferroelectric properties of the PZT thin films differs significantly depending on the use of PT or PZ buffer layers. When the PT buffer layer has five layers, the root mean square roughness (RMS) [17.7 nm] and remnant polarization (Pr) [35.83 μC/cm2] are maximized. On the other hand, when PZ buffer layer has one layer, the RMS [3.67 nm] and Pr [26.08 μC/cm2] are also maximized. The down-graded (Zr composition varying from 0.6 at the bottom surface to 0.4 at top surface) thin films exhibit larger surface roughness and better ferroelectric property than up-graded (Zr composition varying from 0.4 at the bottom surface to 0.6 at top surface) thin films. Therefore, different buffer layer determines different surface morphology. It is concluded that the ferroelectric property of the gradient thin films not only depends on its composition structure, but can also be controlled by the surface morphology. The results indicate that the PZT films with better ferroelectric property should have larger surface roughness.