This paper reviews deposition, integration, and device fabrication of ferroelectric PbZrxTi1-xO3 (PZT) films for applications in microelectromechanical systems. As examples, a piezoelectric ultrasonic micromotor and pyroelectric infrared detector array are presented. A summary of the published data on the piezoelectric properties of PZT thin films is given. The figures of merit for various applications are discussed. Some considerations and results on operation, reliability, and depolarization of PZT thin films are presented.

http://iopscience.iop.org/article/10.1088/0960-1317/10/2/307/pdf

Ferroelectric thin films for micro-sensors and actuators: a review

https://dr.ntu.edu.sg/bitstream/10356/101824/1/A%20comprehensive%20review%20on%20the%20progress%20of%20lead%20zirconate-based%20antiferroelectric%20materials.pdf

A comprehensive review on the progress of lead zirconate-based antiferroelectric materials

This paper provides a detailed overview of developments in transducer materials technology relating to their current and future applications in micro-scale devices. Recent advances in piezoelectric, magnetostrictive and shape-memory alloy systems are discussed and emerging transducer materials such as magnetic nanoparticles, expandable micro-spheres and conductive polymers are introduced. Materials properties, transducer mechanisms and end applications are described and the potential for integration of the materials with ancillary systems components is viewed as an essential consideration. The review concludes with a short discussion of structural polymers that are extending the range of micro-fabrication techniques available to designers and production engineers beyond the limitations of silicon fabrication technology.

/pdf/new-materials-for-micro-scale-sensors-and-actuators-an-21qnaonn0l.pdf

New materials for micro-scale sensors and actuators An engineering review

The use of chemical solution deposition for the fabrication of perovskite thin films is reviewed. A variety of approaches including sol−gel, chelate, and metalloorganic decomposition have all been employed with success in the preparation of these materials. For a number of perovskite compounds, thin-film properties that equal those of the bulk materials have been obtained. Various aspects of the solution chemistries for the three different routes are discussed, and the effects of solution precursor properties on the conversion of the as-deposited film to the desired perovskite phase are discussed. The roles that thermodynamic and kinetic factors have on this transformation process are also reviewed. Finally, some of the applications for solution-derived thin films currently under development are reviewed, and the inherent limitations of the deposition technique for device manufacture are considered.

Chemical Solution Deposition of Perovskite Thin Films

Chemical solution deposition of electronic oxide films

A two-step seeding process has been developed to lower the transformation temperature and modify the grain structure of ferroelectric lead zirconate titanate (PZT) thin films with high Zr/Ti ratio. Previous study has shown that nucleation is the rate-limiting step for the perovskite formation. Therefore, any process that enhances the kinetics of nucleation is likely to decrease the transformation temperature. In this process, a very thin (45 nm) seeding layer of PbTiO3, which has a low effective activation energy for perovskite formation, was used to provide nucleation sites needed for the low temperature perovskite formation. In this study, we have shown that the pyrochlore-to-perovskite phase transformation temperature of PbZrxTi1−xO3 films of high Zr/Ti ratio (e.g., x = 53/47) can be lowered by as much as 100 °C. The grain size of these films can also be substantially modified by this two-step approach.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0884291400019427

Low temperature perovskite formation of lead zirconate titanate thin films by a seeding process

Pyrochlore to perovskite phase transformation in sol‐gel derived lead‐zirconate‐titanate (PZT) films was studied by x‐ray diffraction and transmission‐electron microscopy (TEM). X‐ray diffraction studies of PZT films on sapphire substrates indicated that the pyrochlore to perovskite phase transformation was completed at 650 °C. In contrast, TEM investigations of free‐standing PZT films showed that the phase transformation was completed at much higher temperatures. This discrepancy in the behavior of free‐standing films versus films on substrate can be related to the size effect.

/pdf/pyrochlore-to-perovskite-phase-transformation-in-sol-gel-3jreacvv1u.pdf

Pyrochlore to Perovskite phase-transformation in sol-gel derived lead-zirconate-titanate thin-films

The pyrochlore to perovskite transition in sputtered PZT thin films has been studied using SEM and XRD. The films were annealed in the temperature range between 350 °C and 750 °C, and the transition temperature for pyrochlore to perovskite transition was found to be around 525 °C. Isothermal annealing was used to study the nucleation and growth kinetics of the perovskite phase. The results showed a linear growth rate for the perovskite phase, thereby indicating an interface controlled process. Also, the growth was found to be isotropic in two dimensions parallel to the plane of the substrate. The nucleation of the perovskite phase was found to be random. The effective activation energy of the perovskite transition was found to be 494 kJ/mol using Avrami’s approach.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0884291400074513

Formation kinetics of PbZrxTi1−xO3 thin films

A process for producing a ferroelectric lead zirconate titanate dielectric for a semiconductor device by applying a lead titanate seeding layer to a substrate before applying the lead zirconate titanate film, and a semiconductor device produced in accordance with the process. The lead titanate seeding layer allows the subsequent lead zirconate titanate to be annealed at a significantly lower seeding temperature, to lessen interdiffusion among the films, electrodes and substrate and to lessen thermal stresses.

Low temperature seeding process for ferroelectric memory device

The properties of ferroelectric thin films can be significantly influenced by the presence of point defects. The concentration of vacancies presented in these thin films is known to be one of the key parameters causing the degradation of these films when these films are subjected to polarization reversals. p]To study the effects of the vacancy concentration on the ferroelectric properties, sol gel PZT films and powders were annealed in different oxygen partial pressures. For the PZT films, the reduction of oxides to pure metals was not observed even with films annealed at 2×10−5 atmosphere of oxygen partial pressure. Samples annealed at low oxygen partial pressure (for instance, 10−3 and 2×10−5 atmosphere), which has more Pb and O2 depletions and consequently has more Pb and O2 vacancies, cannot be switched easily. The ratios of coercive field after and before fatigue increase as the defect concentrations of the annealed samples increase.

Chi Kong Kwok

Papers

Low temperature perovskite formation of lead zirconate titanate thin films by a seeding process

Pyrochlore to Perovskite phase-transformation in sol-gel derived lead-zirconate-titanate thin-films

Formation kinetics of PbZrxTi1−xO3 thin films

Low temperature seeding process for ferroelectric memory device

Role of Oxygen Vacancies on the Ferroelectric Properties of Pzt Thin Films