Electromechanical properties and fatigue of antiferroelectric (Pb, La) (Zr, Sn, Ti)O3 thin film cantilevers fabricated by micromachining
Introduction
Micro electromechanical systems (MEMSs) with improved performance are demanded for a great variety of applications. Electromechanical on/off actuation and switch are often required in many MEMS as the basic operations [1], [2]. Due to the RC (resistance–capacitance) delay in electrical circuits, an ideal digital on/off electric signal can never be generated. Consequently conventional electrostatic or piezoelectric mechanisms often cannot effectively provide the real digital on/off states as required in high-speed digital switches. The stability of the digital actuation in MEMS under cyclic loadings is another issue to be solved.
Antiferroelectrics (AFEs) are promising for providing the on-off actuation as required, due to their strain resulted from the electric field induced AFE to ferroelectric (FE) transformation. Their strain behavior in response to the electric field simulates a real digital response to an electric signal with response time of about 90 ns as reported in literature, limited by the phase transition speed [3]. Although the response time of the actuator is limited by its mechanical resonance frequency and (resistance–capacitance) delay, optimization of the device parameters with highly miniaturized designs could be done to make use of the intrinsic fast response of the AFE thin films.
The strains in some AFEs induced during the phase transformations could be larger than those induced in piezoelectric materials [4], [5], [6]. In addition, some reports have shown that AFEs could possibly have higher electric-fatigue strength than piezoelectrics in ferroelectrics under bipolar voltage loading [7], [8], [9], [10], [11]. AFEs are mainly composed of 180° domains. During the AFE–FE switching, the direction of polarization changes only by 180° which results in smaller internal stress than those generated in FEs during the switching of spontaneous polarization by 90°. Consequently under a cyclic loading, less defects and micro-cracks could be formed in AFEs, resulting in higher electric-fatigue strength. There is no depoling issue for AFEs as compared with ferroelectrics without a substantial bias. For applications of ferroelectric thin films even under unipolar condition, large bias could result in accelerated property degradation. It is reported that the remnant polarization of ferroelectric thin films under large bias above the coercive field could even decrease to 20% of its initial value after 105 cycles [12]. In comparison to the ferroelectric thin films with bias, AFEs could show much larger fatigue strength due to the much smaller locally injected power density and consequently less phase decomposition probability in AFEs [12].
Beside large strain and potential high fatigue endurance, no electrical poling process is required for AFEs. This is another important advantage of AFEs over FEs, where FEs should usually be poled before the application in MEMS devices, which is a time and labor consuming process.
There have been many efforts made for investigating the structure and properties of AFE thin films [13], [14], [15], [16], [17]. However, the strain-fatigue behavior of AFE thin films has not been studied yet, which is very critical for device applications. The electromechanical responses of micro-machined structures comprising AFE thin film with on-off switch function need be investigated. To the best of our knowledge, there is no such a study either. Although Yang et al. have recently suggested a fabrication process for AFE (Pb, La) (Zr, Ti)O3 based micro-cantilevers, they have not reported any functional characteristics of the cantilevers [18]. Here, for the first time, we report the electro-mechanical responses and the strain-fatigue behavior of AFE (Pb0.97, La0.02) (Zr0.90, Sn0.05, Ti0.05)O3 (PLZST) thin film cantilevers micro-machined on silicon wafers.
Section snippets
Experimental procedure
The chemical solution deposition process, structure, and the electrical properties of the AFE (Pb0.97, La0.02) (Zr0.90, Sn0.05, Ti0.05)O3 (PLZST) thin films were reported in our previous publication [19]. Cantilevers comprising thin layers of Si, SiO2, Ti/Pt, AFE PLZST, and Ni were fabricated on 4-in. silicon wafer through a series of thin film deposition, patterning, and Si bulk micromachining steps. The Ni and Pt layers were DC-sputtered to form the sandwich electrode structure. The top Ni
Results and discussion
The cross-section of the PLZST multilayer was examined with an SEM, as shown in Fig. 2(a). An SEM image for an obtained PLZST cantilever with bonding pads is shown in Fig. 2(b). The cantilevers were composed of 18-μm Si, 1-μm SiO2, 0.5-μm Pt bottom electrode, 1.2-μm PLZST, and 0.1-μm Ni top electrode layers. The length and width of the cantilevers were fixed at 4 mm and 1 mm respectively. The residual stress measurements by XRD using sin2 ψ method [21] revealed a 60 MPa tensile residual stress in
Conclusions
Antiferroelectric cantilevers comprising a laminate of Ni/PLZST/Pt/Ti/SiO2/Si were fabricated through bulk micro-machining process on silicon wafers. The antiferroelectric cantilevers showed the distinct digital actuation characteristics with the strain generated due to the antiferroelectric–ferroelectric transformation. The maximum displacement per unit voltage around the phase switching field reached 16.7 μm/V, significantly larger than the typical piezoelectric cantilevers. The effective d
Acknowledgement
The authors would like to acknowledge the research grant support (IMRE/10-1C0109) from Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology and Research), Singapore.
References (31)
- et al.
Stability of phases in modified lead zirconate with variation in pressure, electric field, temperature and composition
Journal of Physics and Chemistry of Solids
(1964) - et al.
Electrical fatigue of ferroelectric PbZr0.5Ti0.5O3 and antiferroelectric PbZrO3 thin films
Materials Research Bulletin
(2000) - et al.
Deflection of wafers and cantilevers with Pt/LNO/PZT/LNO/Pt/Ti/SiO2 multilayered structure
Thin Solid Films
(2008) - et al.
A fully packaged piezoelectric switch with low-voltage actuation and electrostatic hold
Proceedings of the MEMS
(2010) - et al.
Micro-Electromechanical-System (MEMS) based switches for power applications
I&CPS
(2011) - et al.
Growth and study of antiferroelectric lead zirconate thin films by pulsed laser ablation
Journal of Applied Physics
(1999) - et al.
Antiferroelectric to ferroelectric phase switching thin films in the lead zirconate stannate titanate solid solution system
- et al.
Dielectric properties and field-induced phase switching of lead zirconate titanate stannate antiferroelectric thick films on silicon substrates
Journal of Applied Physics
(2000) - et al.
Effect of composition and temperature on electric fatigue of La-doped lead zirconate titanate ceramics
Journal of Applied Physics
(1994) - et al.
Electric fatigue in antiferroelectric and ferroelectric Pb(Zr, Sn, Ti)NbO3 thin films prepared by sol–gel process
Japanese Journal of Applied Physics
(1998)
Electric fatigue properties of Pb-based ferroelectric and antiferroelectric thin films
Ferroelectrics
Why do antiferroelectrics show higher fatigue resistance than ferroelectrics under bipolar electrical cycling?
Applied Physics Letters
Polarization fatigue in ferroelectric thin films and related materials
Journal of Applied Physics
Transducer using the electric field-forced antiferroelectric–ferroelectric transition
Ultrasonics
Transducers using forced transitions between ferroelectric and antiferroelectric states
IEEE Transactions on Sonics and Ultrasonics
Cited by (18)
Dielectric, piezoelectric and electrostrictive properties of antiferroelectric lead-zirconate thin films
2022, Journal of Alloys and CompoundsCitation Excerpt :Antiferroelectric materials show a double hysteresis loop in the polarization versus electric field characteristics, P(E), presenting interest for energy storage application [1,2]. This family of materials also exhibits large strain, useful for actuators and sensors [2–5]. In this context, materials such as pure or doped PbZrO3 (PZO) have been widely studied [6–9].
Hierarchical domain structures in (Pb,La)(Zr, Sn, Ti)O<inf>3</inf> antiferroelectric ceramics
2020, Ceramics InternationalCitation Excerpt :For example, the nanodomains have been considered to be responsible for the ultrahigh piezoelectric properties of Pb(Zr, Ti)O3 [4] with composition located at the morphotropic phase boundary (MPB) and dielectric dispersion in relaxor Pb(Mg, Nb)O3 [5–7]. Compared with the extensive researches of FE domains, antiferroelectric (AFE) domains are less studied but are drawing more and more attentions in recent decades since the AFE materials are expected to have important application in microactuators [8,9], energy storage [10–15], cooling devices [16,17], etc. The promising functionalities of AFE materials originate from the reversible process between the antiparallel dipoles state and the parallel dipoles state under external electric field, temperature or stress field, which mainly manifests itself in the evolution of crystal structure and domain structure [16,18,19].
Large-displacement actuating and high-frequency vibrating characteristics of silicon-based antiferroelectric (Pb, La)(Zr, Ti)O<inf>3</inf> thick-film micro-cantilevers
2016, Microelectronic EngineeringCitation Excerpt :In order to meet this challenge, the AFE silicon-based (Pb, La)(Zr, Ti)O3 micro-cantilevers are fabricated by integrating the AFE thick films with the MEMS technology. The actuators made with AFE thick films can be taken an excellent candidate as a micro-positioning mechanism due to the bigger displacement, faster response and lower driving voltage than other types of micro- actuators [6–9]. With the electrostriction behavior of AFE materials, the AFE micro-cantilever is an electrical-field-induced micro-actuator when transiting from the AFE phase to the ferroelectric (FE) one.
Polarization fatigue in antiferroelectric (Pb,La)(Zr,Ti)O<inf>3</inf> thin films: The role of the effective strength of driving waveform
2015, Ceramics InternationalCitation Excerpt :However, practical materialization of AFEs involves being exposed to several obstacles. For instance, to achieve the best performances, AFE materials usually operate under a high repetitive ac/dc field [3,7,8]. In this regard, excellent fatigue resistance is of great importance to guarantee the reliability of AFE-based devices.
Effective driving voltage on polarization fatigue in (Pb,La)(Zr,Ti)O<inf>3</inf> antiferroelectric thin films
2015, Ceramics International