Jean Costecalde

Enhancement of energy storage in epitaxial PbZrO3 antiferroelectric films using strain engineering

We demonstrate an approach to enhance the energy storage density W of antiferroelectric film through simple altering a crystallographic orientation of the substrate. We reveal that the antiferroelectric phase stability of PbZrO3 can be enhanced for the (110) or (111) SrTiO3 substrate orientation, thus suppresses the antiferroelectric-ferroelectric phase transition to higher electric field with ∼120 kV/cm increment. In addition, the polarization values of these films are also favorably increased hence increases W by 5.3 J/cm3 at 700 kV/cm. The observed enhancement is found to originate from a high sensitivity of phase transition to mechanical confinements due to the volume expansion at the transition.

Effect of residual stress on energy storage property in PbZrO3 antiferroelectric thin films with different orientations

The effect of residual stress on energy storage property was investigated for a series of PbZrO3 thin films on SrTiO3 and Si substrates. Compressive or tensile residual stress influences the critical electric field EA for the ferroelectric-to-antiferroelectric phase transition, thus for films with (110)/(101) orientation, energy density W of films on SrTiO3 is 38% larger than films on Si; in contrast, (001)-oriented PbZrO3 films on SrTiO3 show slightly smaller W compared to films on Si. We conclude that the different responses of W to stress are related to the different constrain states in films with different orientations.

Wafer-scale fabrication of self-actuated piezoelectric nanoelectromechanical resonators based on lead zirconate titanate (PZT)

In this paper we report an unprecedented level of integration of self-actuated nanoelectromechanical system (NEMS) resonators based on a 150 nm thick lead zirconate titanate (PZT) thin film at the wafer-scale. A top-down approach combining ultraviolet (UV) lithography with other standard planar processing technologies allows us to achieve high-throughput manufacturing. Multilayer stack cantilevers with different geometries have been implemented with measured fundamental resonant frequencies in the megahertz range and Q-factor values ranging from ~130 in air up to ~900 in a vacuum at room temperature. A refined finite element model taking into account the exact configuration of the piezoelectric stack is proposed and demonstrates the importance of considering the dependence of the beam’s cross-section upon the axial coordinate. We extensively investigate both experimentally and theoretically the transduction efficiency of the implemented piezoelectric layer and report for the first time at this integration level a piezoelectric constant of d31 = 15 fm.V−1. Finally, we discuss the current limitations to achieve piezoelectric detection.

Low-temperature crystallization of high performance Pb0.4Sr0.6TiO3 films compatible with the current silicon-based microelectronic technology

This investigation presents a simple approach to realize the low temperature crystallization of Pb0.4Sr0.6TiO3 thin films at 400 °C by taking advantage of well controlled lead excess and kinetic-driving-force compensated thermodynamics crystalline via sputtering deposition. The thin films prepared at low temperature show fine-grained micro-structure because of the suppressed grain growth, furthermore, the intrinsic dielectric response can be modulated by the distinct level of crystallinity. The film processed at 450 °C exhibited a dielectric constant of 435 and high figure merit of 130 at 400 kV/cm, superior ferroelectric property, and stable performance with temperature and frequency.

Lead-zirconate titanate (PZT) nanoscale patterning by ultraviolet-based lithography lift-off technique for nano-electromechanical systems applications

The advantage of using lead zirconate-titanate (PbZr 0.54 Ti 0.46 O 3 ) ceramics as an active material in nano-electromechanical systems (NEMS) comes from its relatively high piezoelectric coefficients. However, its integration within a technological process is limited by the difficulty of structuring this material with submicrometer resolution at the wafer scale. In this work, we are developed a specific patterning method based on optical lithography coupled with a dual layer resist process. The main objective is to obtain sub-micron features by lifting off a 100 nm thick PZT layer while preserving the materials piezoelectric properties. A subsequent result of the developed method is the ability to stack several layers with a lateral resolution of few tens of nanometers, which is mandatory for the fabrication of NEMS with integrated actuation and read-out capabilities.