Effect of multi-coating process on the orientation and microstructure of lead zirconate titanate (PZT) thin films derived by chemical solution deposition

This paper describes the effects of multi-coating processes on the orientation, microstructure and electrical property of lead zirconate titanate (PZT) thick films derived by chemical solution deposition. PZT thick films (> 1 μm in thickness) were deposited by various multi-coating processes, such as layer-by-layer crystallization, seed-layering or single-crystallization. The orientation and microstructure of the thick films were characterized by X-ray diffractometry and scanning electron microscopy. For the layer-by-layer crystallization process, repeated deposition, pyrolysis at 470 or 250°C and rapid thermal annealing (RTA) were carried out. When pyrolyzed at 470°C, the resulting films were found to be (111)-oriented with a columnar structure. When pyrolysis temperature was 250°C, the thick films were found to be (100)-oriented with a columnar structure. For seed-layering, single-coated (100)-oriented PZT thin films were utilized as a seed layer. Thick films were fabricated by repeating deposition onto the seed layer, then pyrolysis at 470°C, followed by a single RTA. We found that the upper side of the thick films was randomly oriented with a granular structure and their bottom side was (100)-oriented with a columnar structure. For the single-crystallization process, repeated deposition and pyrolysis at 470°C followed by a single RTA resulted in randomly oriented PZT thick films with a granular structure. Electrical measurements of the (111)-oriented PZT thick films revealed a 750 dielectric constant, 21 μC/cm² remnant polarization and 50 kV/cm coercive field. The same properties for the (100)-oriented PZT thick films were 1250, 14 μC/cm² and 29 kV/cm, respectively.