Size effects in mechanical behavior of submicron and nanometer thick textured Pt films

{111}-textured Platinum (Pt) thin films facilitate the growth of {001}-textured PZT films with high transverse piezoelectric coefficients, and serve as the electrodes for PZT films for MEMS. However, the film thickness, texture, and strain rate dependent mechanical behavior of magnetron sputtered {111}-textured freestanding Pt films are unknown, and are expected to control failure initiation of the PZT films. To this goal, freestanding Pt films with thicknesses of 50, 150, 200, 500, and 1000 nm and perfect {111}-texture were studied via uniaxial tension experiments at strain rates 10-6 ? 10 s–1. The elastic modulus, E = 164 ± 8 GPa, was independent of strain rate and film-thickness and was in very good agreement with theoretical estimates for the in-plane modulus of {111}-textured polycrystalline Pt. The yield stress increased with decreasing film-thickness: thicker films, 500 and 1000 nm, yielded early and accumulated larger plastic strain (~0.6–0.7%) when compared with the 200- and 150-nm Pt films that accumulated only 0.15% plastic strain, and the 50-nm films that failed in a brittle manner. This thickness dependence could be the result of both intergranular (grain rotation, grain boundary sliding) and intragrain (dislocation motion) plasticity taking place in thicker films as compared to only intergranular plasticity taking place in the thinner films. Strain-rate hardening was low for 1000-nm thick films, with strain-rate sensitivity m ~ 0.01, and was practically absent for all other film thicknesses. All films failed at only ~1% strain which may be attributed to localization of slip due to texture. Fracture for the 1000 nm and 500 nm films occurred at ~45o with respect to the loading direction with transgranular features and strain localization, whereas the failure of 200, 150, and 50 nm thick films was brittle

Large displacement vertical translational actuator based on piezoelectric thin films

A novel vertical translational microactuator based on thin-film piezoelectric actuation is presented, using a set of four compound bend-up/bend-down unimorphs to produce translational motion of a moving platform or stage. The actuation material is a chemical-solution deposited lead–zirconate–titanate (PZT) thin film. Prototype designs have shown as much as 120 µm of static displacement, with 80–90 µm displacements being typical, using four 920 µm long by 70 µm legs. Analytical models are presented that accurately describe nonlinear behavior in both static and dynamic operation of prototype stages when the dependence of piezoelectric coefficients on voltage is known. Resonance of the system is observed at a frequency of 200 Hz. The large displacement and high bandwidth of the actuators at low-voltage and low-power levels should make them useful to a variety of optical applications, including endoscopic microscopy.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/85407/1/jmm10_7_075016.pd

A Pb(Zr\u3csub\u3e0.55\u3c/sub\u3eTi\u3csub\u3e0.45\u3c/sub\u3e)O\u3csub\u3e3\u3c/sub\u3e-transduced fully differential mechanically coupled frequency agile filter

This letter reports on the performances of a frequency-tunable lead-zirconate-titanate-transduced fully differential mechanically coupled high-overtone width-extensional filter. The demonstrated electric field tuning provides channel agility and bandwidth adjustability for the incorporation of analog spectral processors in modern radio receiver architectures. We designed and experimentally characterized the higher overtone frequency response of a fully differential width-extensional filter. The filter demonstrates a center frequency (fC) tuning range of 7 MHz at 260 MHz and an adjustable bandwidth from 3 to 6.3 MHz while maintaining a maximum frequency shift due to hysteresis effects below 0.14% and a stopband rejection floor of -60 dB

PZT transduction of high-overtone contour-mode resonators

This paper presents the Butterworth-van Dyke model and quantitative comparison that explore the design space of lead zirconate titanate-only (PZT) and PZT on 3-, 5-, and 10-μm single-crystal silicon (SCS) high-overtone width-extensional mode (WEM) resonators with identical lateral dimensions for incorporation into radio frequency microelectromechanical systems (RF MEMS) filters and oscillators. A novel fabrication technique was developed to fabricate the resonators with and without a silicon carrier layer using the same mask set on the same wafer. The air-bridge metal routings were implemented to carry electrical signals while avoiding large capacitances from the bond-pads. We theoretically derived and experimentally measured the correlation of motional impedance (RX), quality factor (Q), and resonance frequency (f) with the resonators\u27 silicon layer thickness (tSi) up to frequencies of operation above 1 GHz

PZT transduced high-overtone width-extensional resonators above 1 GHz

This paper provides the theoretical modeling, simulation, and quantitative comparison that explore the design space of PZT-only (Lead Zirconate Titanate) and PZT-on 3, 5 and 10 μm single-crystal silicon high-overtone width-extensional mode (WEM) resonators with identical lateral dimensions for incorporation into radio frequency microelectromechanical systems (RF MEMS) filters and oscillators. A novel fabrication technique was developed to fabricate the resonators with and without silicon layer using the same mask-set on the same wafer. The air-bridge metal routings were implemented to carry electrical signals while avoiding large capacitances from the bond-pads. We theoretically verified and experimentally measured the correlation of motional impedance (RX), quality factor (Q), and resonance frequency (f) with the resonators\u27 silicon layer thickness (tSi) up to above 1 GHz frequency of operation. For identical lateral dimensions and PZT-layer thickness (tPZT), the resonators with thicker silicon layer have higher f. The resonators with thicker silicon also have higher Q and lower RX up to 900 MHz frequency

Performance comparison of Pb(Zr\u3csub\u3e0.52\u3c/sub\u3eTi\u3csub\u3e0.48\u3c/sub\u3e)O\u3csub\u3e3\u3c/sub\u3e-only and Pb(Zr\u3csub\u3e0.52\u3c/sub\u3eTi\u3csub\u3e0.48\u3c/sub\u3e)O\u3csub\u3e3\u3c/sub\u3e-on-silicon resonators

This paper provides a quantitative comparison and explores the design space of lead zirconium titanate (PZT)–only and PZT-on-silicon length-extensional mode resonators for incorporation into radio frequency microelectromechanical system filters and oscillators. We experimentally measured the correlation of motional impedance (RX) and quality factor (Q) with the resonators’ silicon layer thickness (tSi). For identical lateral dimensions and PZT-layer thicknesses (tPZT), the PZT-on-silicon resonator has higher resonant frequency (fC), higher Q (5100 versus 140), lower RX (51 Ω versus 205 Ω), and better linearity [third-order input intercept point (IIP3) of +43.7 dBm versus +23.3 dBm]. In contrast, the PZT-only resonator demonstrated much wider frequency tuning range (5.1% versus 0.2%)

Fatigue-induced grain coarsening in nanocrystalline platinum films

Mechanisms to explain the unique mechanical behavior of nanograined metals focus primarily on grain and grain boundary mobility. In most nanograined metal materials systems (both pure and alloyed) it has not been possible to decouple these time- and cycle-dependent contributions. In contrast, the 460 nm thick, (1 1 1) textured, nanograined platinum thin films evaluated in this work have robust grain morphologies that allow us to uniquely identify the fatigue damage accumulation processes. Unlike other reports of face-centered cubic metal behavior, the platinum films exhibited a particularly limited range of fatigue crack growth (\u3c3 MPa √m) with extremely large (~10.5) power law exponents typically associated with fatigue of structural ceramics and ordered intermetallics. Transmission electron microscopy and fatigue crack growth data suggest that the crack growth mechanism appears to be intrinsic in origin and dislocation mediated