**1. Introduction**

Highly integrated nano-ferroelectric/piezoelectric devices with Si-CMOS technology require a low-processing temperature (≤450°C) of ferroelectric/piezoelectric films [1]. Among ferroelectric/piezoelectric materials, lead zirconium titanate (PZT) [2] appears as the most promising candidate because of its excellent structural and electrical properties, in addition to its

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

relatively low processing temperature (~600°C) compared to organic, lead-free, and the other inorganic materials [3, 4].

Many efforts have been done for lowering the process temperature of device-quality PZT films to below 450°C such as the chemical vapor deposition [5], pulse laser deposition [6], and sputtering [7]. However, most of these technologies are costly and complicated, which are not suitable for practical applications. On the other hand, the chemical solution deposition (CSD) technique offers many advantages such as simplicity, low-cost, large area deposition, and feasibility of material compositional control. Many low-temperature CSD methods, including tailoring precursor solution [8, 9], seeding the film [10], hydrothermal annealing [11], and better lattice matching [12], have been investigated, but all provide insufficient film quality and compromised properties. Hitherto, the relatively successful approaches have been microwave annealing [13], localized heating by pulse laser [14], and ultraviolet-assisted annealing [15]. Nevertheless, microwave heating results in damage of CMOS circuits, while the costly pulse laser processing is unfavorable for industrial application.

This chapter presents a critical review on the low-temperature solution-processed PZT films and devices since last 15 years, and addresses challenges for fundamental understanding and practical integration of multifunctional PZT films in devices. Database collection was performed using major searching engines such as ISI Web of Science (Thomson Reuters) and Google Scholar. In the first part, recent advances in fabrication of CSD-derived PZT films at a low temperature (≤450°C) using chemical and physical approaches are thoroughly reviewed. The second part discusses various techniques such as wet/dry-etching, lift-off, and imprinting for patterning PZT into micro-nano-sized patterns. Lastly, some potential applications of the low-temperature CSDderived PZT films and devices for sensor/actuator and energy harvesting are demonstrated.

energy [17]. The seeded PZT films showed a lesser (111)-preferential orientation, greater nucleation density, and a better ferroelectricity. The formation of the metastable intermetallic

seeded films [18]. The obtained dielectric permittivity (ε), remnant polarization (*Pr*

) of the 430°C-pyrolyzed seed-PZT film were 500, 6.71 μC/cm2

PZT thin films deposited on a platinized substrate, which greatly influences on crystallization temperature, microstructure, and electrical properties of resulting films [18, 19]. This metastable phase forms at around 330°C and disappears as elevated heating (**Figure 1**). The pyrolysis and annealing conditions as well as the film thickness determine the formation of this intermetallic phase. These conditions impact on the reduction of Pb2+ into Pb, which drives the formation of

than directly on Pt. This explains why the formation of PZT(111) phase is facilitated by the intermediate ones (**Figure 2**) [20]. Due to very small lattice mismatch (0.4%) between the PbPt<sup>3</sup>

PZT phases, the nucleation activation energy might be reduced. As a result, well (111)-oriented perovskite PZT was able to be fabricated at 440–480°C. The PZT film exhibited a good quality

Solvothermal synthesis is a method of crystallizing solution-derived materials under a high pressure and at a temperature higher than boiling temperatures of used solvents. The method

phase. The perovskite nucleation was found on top of the intermetallic phase rather

and a *Pr*

of 24 μC/cm2

[20].

Pb interlayer, between the film and the Pt electrode layer, was also observed. However, the local random perovskite nucleation might result in the decreased (111) orientation of the

Lead Zirconium Titanate Films and Devices Made by a Low-Temperature Solution-Based Process

), and coer-

and

, and 80 kV/cm,

phase is formed in the early stages of pyrolysis for

phase and perovskite PZT for the three-layer films

http://dx.doi.org/10.5772/intechopen.79378

91

Ptx

cive field (*Ec*

dried at 200°C [19].

respectively.

the PbPt3

*2.1.2. Formation of an early stage seeded PbPtx layer*

**Figure 1.** Temperature-time-texture diagram for the metastable PbPt3

with a pyroelectric coefficient of 1.8 × 10−<sup>4</sup> Cm−<sup>2</sup> K−<sup>1</sup>

*2.1.3. Solvothermal synthesis*

It has been reported that an intermetallic PbPt3
