Laser Lift-off Processing of PZT Thin Films for Improved Piezoelectric-based Microelectromechanical Systems PDF Download
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Author: Loucas Tsakalakos
Publisher:
ISBN:
Category :
Languages : en
Pages : 220
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Author: Loucas Tsakalakos
Publisher:
ISBN:
Category :
Languages : en
Pages : 220
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Author: Kirsten L. Brookshire
Publisher:
ISBN:
Category : Microelectromechanical systems
Languages : en
Pages : 126
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Pb(Zr, Ti)O3 (PZT) is a very attractive material for use in piezoelectric-based microelectromechanical systems (MEMS) due to its high piezoelectric coefficients and ability for large displacements with relatively low applied fields (as compared to electrostatic-based MEMS). The piezoelectric effect is strongly anisotropic, thus it is very desirable to control the crystallographic orientation of the active material. This study is designed to understand the effect of crystallographic texture on the long-term stability of piezoelectric-based MEMS devices. Utilizing (100)-oriented solution deposited LaNiO3 (LNO) and PbTiO3 (PT) seed layers, (001) fiber texture of rfmagnetron sputtered PZT films (ex situ annealed) with varying thickness was optimized. X-ray diffraction rocking curve data indicated good out-of-plane alignment, with full-width-at-half-maximum (FWHM) values of 3.8° - 4.5° and 2.5°- 3.1° for PZT on LNO and PT, respectively. This optimization of (001) orientation is paramount to maximizing the piezoelectric response of PZT thin films for MEMS applications, as this promotes the highest piezoelectric response. Dielectric and ferroelectric properties were obtained for films 120-1320 nm thick. Subsequently these films were subjected to lifetime (fatigue) tests similar to what is experienced in piezo- MEMS applications. Fatigue endurance is a critical factor in evaluating long-term device reliability in these devices. A study of fatigue dependence on film thickness, morphology, bottom electrode, and field strength was conducted. Results of these studies show film morphology contributes strongly to film fatigue and film failure prior to reaching 108 fatigue cycles, with increased grain size leading to improved fatigue endurance. Film thickness was also shown to contribute significantly to fatigue, predominantly in PZT on PT films, with films over 1 [micrometer] in thickness showing large fatigue after 108 cycles. Films with bottom LNO electrodes demonstrated improved performance over all thickness ranges studied when compared to PT bottom electrodes, exhibiting minimal fatigue after 108 cycles.
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Publisher: The Electrochemical Society
ISBN: 9781566774222
Category : Microelectromechanical systems
Languages : en
Pages : 352
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Author: Shi Yin
Publisher:
ISBN:
Category :
Languages : en
Pages : 194
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Recently, piezoelectric materials, like lead titanate zirconate Pb(ZrxTi1-x)O3 (PZT), zinc oxide ZnO, and the solid solution Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT), increasingly receive intensive studies because of their innovative applications in the microelectromechanical systems (MEMS). In order to integrate them on silicon substrate, several preliminaries must be taken into considerations, e.g. buffer layer, bottom electrode. In this thesis, piezoelectric films (PZT and PMN-PT) have been successfully epitaxially grown on silicon and SOI (silicon-on-insulator) in the form of single crystal by sol-gel process. In fact, recent studies show that single crystalline films seem to possess the superior properties than that of polycrystalline films, leading to an increase of the performance of MEMS devices. The first objective of this thesis was to realize the epitaxial growth of single crystalline film of piezoelectric materials on silicon. The use of a buffer layer of gadolinium oxide(Gd2O3) or strontium titanate (SrTiO3 or STO) deposited by molecular beam epitaxy (MBE) has been studied in detail to integrate epitaxial PZT and PMN-PT films on silicon. For Gd2O3/Si(111) system, the study of X-ray diffraction (XRD) on the growth of PZT film shows that the film is polycrystalline with coexistence of the nonferroelectric parasite phase, i.e. pyrochlore phase. On the other hand, the PZT film deposited on STO/Si(001) substrate is successfully epitaxially grown in the form of single crystalline film. In order to measure the electrical properties, a layer of strontium ruthenate (SrRuO3 or SRO) deposited by pulsed laser deposition (PLD) has been employed for bottom electrode due to its excellent conductivity and perovskite crystalline structure similar to that of PZT. The electrical characterization on Ru/PZT/SRO capacitors demonstrates good ferroelectric properties with the presence of hysteresis loop. Besides, the relaxor ferroelectric PMN-PT has been also epitaxially grown on STO/Si and confirmed by XRD and transmission electrical microscopy (TEM). This single crystalline film has the perovskite phase without the appearance of pyrochlore. Moreover, the study of infrared transmission using synchrotron radiation has proven a diffused phase transition over a large range of temperature, indicating a typical relaxor ferroelectric material. The other interesting in the single crystalline PZT films deposited on silicon and SOI is to employ them in the application of MEMS devices, where the standard silicon techniques are used. The microfabrication process performed in the cleanroom has permitted to realize cantilevers and membranes in order to mechanically characterize the piezoelectric layers. Mechanical deflection under the application of an electric voltage could be detected by interferometry. Eventually, this characterization by interferometry has been studied using the modeling based on finite element method and analytic method. In the future, it will be necessary to optimize the microfabrication process of MEMS devices based on single crystalline piezoelectric films in order to ameliorate the electromechanical performance. Finally, the characterizations at MEMS device level must be developed for their utilization in the future applications.
Author: Alper Erturk
Publisher: John Wiley & Sons
ISBN: 1119991358
Category : Technology & Engineering
Languages : en
Pages : 377
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Book Description
The transformation of vibrations into electric energy through the use of piezoelectric devices is an exciting and rapidly developing area of research with a widening range of applications constantly materialising. With Piezoelectric Energy Harvesting, world-leading researchers provide a timely and comprehensive coverage of the electromechanical modelling and applications of piezoelectric energy harvesters. They present principal modelling approaches, synthesizing fundamental material related to mechanical, aerospace, civil, electrical and materials engineering disciplines for vibration-based energy harvesting using piezoelectric transduction. Piezoelectric Energy Harvesting provides the first comprehensive treatment of distributed-parameter electromechanical modelling for piezoelectric energy harvesting with extensive case studies including experimental validations, and is the first book to address modelling of various forms of excitation in piezoelectric energy harvesting, ranging from airflow excitation to moving loads, thus ensuring its relevance to engineers in fields as disparate as aerospace engineering and civil engineering. Coverage includes: Analytical and approximate analytical distributed-parameter electromechanical models with illustrative theoretical case studies as well as extensive experimental validations Several problems of piezoelectric energy harvesting ranging from simple harmonic excitation to random vibrations Details of introducing and modelling piezoelectric coupling for various problems Modelling and exploiting nonlinear dynamics for performance enhancement, supported with experimental verifications Applications ranging from moving load excitation of slender bridges to airflow excitation of aeroelastic sections A review of standard nonlinear energy harvesting circuits with modelling aspects.
Author: Swetapadma Praharaj
Publisher: CRC Press
ISBN: 1003803849
Category : Technology & Engineering
Languages : en
Pages : 211
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Book Description
This book explains the state-of-the-art green piezoelectric energy harvesting (PEH) technology. It highlights different aspects of PEH, starting right from the materials, their synthesis, and characterization techniques to applications. Various types of materials, including ceramics, polymers, composites, and bio-inspired compounds in nano, micro, and meso scale and their recent advancements are captured in detail with special focus on lead-free systems. Different challenges and issues faced while designing a PEH are also included. Features: Guides on how to harvest piezoelectric energy in a sustainable manner Describes related figures of merit for piezoelectric energy harvesting Covers synthesis of piezoelectric materials in the form of bulk, single crystal, nano, and thin/thick film Includes pertinent advanced characterization techniques Reviews piezo-energy harvesting devices and structures This book is aimed at researchers, professionals, and graduate students in electrical engineering, materials, and energy.
Author: Charles Yeager
Publisher:
ISBN:
Category :
Languages : en
Pages :
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This thesis describes the optimization of piezoelectric Pb(ZrxTi1-x)O3 (PZT) thin films for energy generation by mechanical energy harvesting, and self-powered micro-electro-mechanical systems (MEMS). For this purpose, optimization of the material was studied, as was the incorporation of piezoelectric films into low frequency mechanical harvesters. A systematic analysis of the energy harvesting figure of merit was made. As a figure of merit (e31,f)2/[epsilon]r (transverse piezoelectric coefficient squared over relative permittivity) was utilized. PZT films of several tetragonal compositions were grown on CaF2, MgO, SrTiO3, and Si substrates, thereby separating the dependence of composition on domain orientation. To minimize artifacts associated with composition gradients, and to extend the temperature growth window, PZT films were grown by metal organic chemical vapor deposition (MOCVD). Using this method, epitaxial {001} films achieved c-domain textures above 90% on single crystal MgO and CaF2 substrates. This could be tailored via the thermal stresses established by the differences in thermal expansion coefficients of the film and the substrate. The 001 single-domain e31,f for PZT thin films was determined to exceed -12 C/m2 in the tetragonal phase field for x >= 0.19, nearly twice the phenomenologically modeled value. The utilization of c-domain PZT films is motivated by a figure of merit above 0.8 C2/m4 for (001) PZT thin films. Increases to the FoM via doping and hot poling were also quantified; a 1% Mn doping reduced [epsilon]r by 20% without decreasing the piezoelectric coefficient. Hot poling a device for one hour above 120 °C also resulted in a 20% reduction in [epsilon]r; furthermore, 1% Mn doping reduced [epsilon]r by another 12% upon hot poling. Two methods for fabricating thin film mechanical energy harvesting devices were investigated. It was found that phosphoric acid solutions could be used to pattern MgO crystals, but this was typically accompanied by damage to the PZT film. An energy harvester was fabricated by etching the MgO substrate down to 10-20 [mu]m under a circular diaphragm device; this structure had a natural frequency of 2.7 kHz and was estimated to provide a maximum RMS power of 8.8 [mu]W/cm2g2. Due to the lack of selectivity in the patterning, MgO was not as versatile as silicon substrates, which can be etched rapidly by wet and dry methods.To successfully release a PZT film onto a polymer passive elastic layer, dry (gas) etch methods were preferable. This protected the interfacial bonding between PZT films and Parylene. A 2 cm2 thin film membrane (15 [mu]m Parylene/ 3 [mu]m Cyclotene 4022/ 0.1 [mu]m Pt-Ti/ 1.4 [mu]m PZT (52/48)/ 0.14 [mu]m Pt-Ti/ 1 [mu]m SiO2) was released from a silicon substrate and operated with a 5 Hz natural frequency, the lowest reported for a thin film energy harvester operating in resonant excitation. Though problems existed with buckling of the beam due to tension in the Cyclotene 4022 (a benzocyclobutene, BCB, resin) from curing on a silicon substrate, the cantilevered device was calculated to output up to RMS 0.53 [mu]W/cm2 when swept through an arc >30°. Silicon substrates facilitated scaling in size and quantity of devices compared to MgO substrates, which motivated an investigation into the reduction of 90° domain walls for thin films released from substrate clamping conditions. Circular test structures were designed to produce systematic changes in the clamping condition of {001} PZT thin films. The stiffness of the substrate interface was modified either by using a PZT buffer layer on the substrate or by removing the substrate completely. Films allowed to stress relax upon release, via curling, had reduced domain wall restoring force compared to fully clamped structures, leading to a 72% increase in irreversible domain wall contributions for free-standing 300 [mu]m features. The irreversible dielectric Raleigh coefficient, [alpha], for a 1.64 [mu]m {001} PZT film measured at 20 Hz increased from 40 cm/kV to 71 cm/kV in this way. Griggio et al., Phys. Rev. Let. 108, no. 15 (2012) 157604 reported [alpha] of 148 cm/kV at 100 Hz for broken sections of 70 [mu]m diaphragms. To understand the relationship between [alpha] reported in those experiments and the results of this thesis, the size dependence of [alpha] was investigated by partitioning 300 [mu]m diaphragms into wedges. Both [alpha] and the frequency dispersion of [alpha] increased as the membrane was sectioned. This was attributed to a decrease in the elastic restoring force for domain walls. Interface (local) stresses were found to have a smaller impact on domain wall mobility, even after the domain structure was annealed above the Curie temperature post release.
Author:
Publisher:
ISBN:
Category : Microactuators
Languages : en
Pages : 378
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Author: Maryam Abazari Torghabeh
Publisher:
ISBN:
Category : Ferroelectric devices
Languages : en
Pages : 193
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As a high performance piezoelectric material widely used in sensors, actuators and other electronic devices, lead zirconate titanate (PZT) ceramics have been the center of attention for many years. However, the toxicity of these materials and their exposure to the environment during processing steps, such as calcination, sintering, machining as well as problems in recycling and disposal have been major concerns regarding their usage all around the globe for the past couple of decades. Consequently, utilizing lead-based materials for many commercial applications have been recently restricted in Europe and Asia and measures are being taken in United States as well. Therefore, there is an urgent need for lead-free piezoelectrics whose properties are comparable to those of well-known PZT materials. Recently, the discovery of ultra-high piezoelectric activity in the ternary lead-free KNaNbO3-LiTaO3-LiSbO3 (KNN-LT-LS) and (Bi, Na)TiO3-(Bi, K)TiO3-BaTiO3 (BNT-BKT-BT) systems have given hope for alternatives to PZT. Furthermore, the demand for new generation of environment-friendly functional devices, utilizing piezoelectric materials, inspired a new surge in lead-free piezoelectric thin film research. In this study, an attempt has been made to explore the development of lead-free piezoelectric thin films by Pulsed Laser Deposition (PLD) on SrTiO3 substrate. While the growth and development process of KNN-LT-LS thin films was the primary goal of this thesis, a preliminary effort was also made to fabricate and characterize BNT-BKT-BT thin films. In a comprehensive and systematic process optimization study in conjunction with X-ray diffractometry, the phase evolution, stoichiometry, and growth orientation of the films are monitored as a function of deposition conditions including temperature and ambient oxygen partial pressure. Processing parameters such as substrate temperature and pressure are shown to be highly dominant in determining the phase and composition of the films. Oxygen partial pressure has shown to control the chemical composition of the films through solid-gaseous phase equilibrium and substrate temperature has mostly influenced the growth mode and microstructure. Findings of this study has shown that 300-500 nm single-phase epitaxial KNN-LT-LS and BNT-BKT-BT thin films could indeed be obtained at a temperature of 700-750 oC and 300-400 mTorr of oxygen partial pressure. Following a series of studies on effect of doping, it was revealed that addition of 1 mol% Mn to KNN-LT-LS composition resulted in a significant suppression of leakage current and enhancement of polarization saturation. A remanent polarization of 16 æC/cm2 and coercive field of 20 kV/cm were measured for such thin film, which are comparable to those of hard PZT counterparts. Also, a high remanent polarization and coercive field of 30 æC/cm2 and 95 kV/cm were achieved in 350 nm BNT-BKT-BT thin films. Longitudinal (d33) and transverse (e31, f) piezoelectric coefficients of KNN-LT-LS thin films were found to be 55 pm/V and -4.5 C/m2 respectively, prepared at the optimized conditions, whereas 350 nm BNT-BKT-BT thin films exhibited an e31, f of -2.25 C/m2. The results of this study present the great potential of KNN-LT-LS and BNT-BKT-BT thin films for piezoelectric MEMS devices and provide a baseline for future investigations on lead-free piezoelectric thin films.
Author: Aimé Peláiz-Barranco
Publisher: BoD – Books on Demand
ISBN: 9535108859
Category : Science
Languages : en
Pages : 546
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Book Description
Ferroelectricity is one of the most studied phenomena in the scientific community due the importance of ferroelectric materials in a wide range of applications including high dielectric constant capacitors, pyroelectric devices, transducers for medical diagnostic, piezoelectric sonars, electrooptic light valves, electromechanical transducers and ferroelectric random access memories. Actually the ferroelectricity at nanoscale receives a great attention to the development of new technologies. The demand for ferroelectric systems with specific applications enforced the in-depth research in addition to the improvement of processing and characterization techniques. This book contains twenty two chapters and offers an up-to-date view of recent research into ferroelectricity. The chapters cover various formulations, their forms (bulk, thin films, ferroelectric liquid crystals), fabrication, properties, theoretical topics and ferroelectricity at nanoscale.
